EPA-67Q/2-74-007
March 1974
Environmental Protection Technology Series
Physical, Chemical, and Microbiological
METHODS OF SOLID WASTE TESTING
Four Additional Procedures
National Environmental Reset
Office of Research and Development
U.S. Environmental Protection Agency
Cincinnati, Ohio 45268
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EPA-67012-74-007
March 1974
Physical
Chemical and
Microbiological
METHODS OF
SOLID WASTE TESTING
Four Additional Procedures
by Nancy S. Ulmer
Program Element No 1OB064
SOLID AND HAZARDOUS WASTE RESEARCH LABORATORY
NATIONAL ENVIRONMENTAL RESEARCH CENTER
OFFICE OF RESEARCH AND DEVELOPMENT
U.S. ENVIRONMENTAL PROTECTION AGENCY
CINCINNATI, OHIO 45268
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REVIEW NOTICE
The National Environmental Research Center, Cincinnati, U.S.
Environmental Protection Agency, has reviewed this report and approved its
publication. Mention of trade names or commercial products does not
constitute endorsement or recommendation for use.
11
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FOREWORD
Man and his environment must be protected from the adverse
effects of pesticides, radiation, noise and other forms of pollution, and the
unwise management of solid waste. Efforts to protect the environment
require a focus that recognizes the interplay between the components of our
physical environment - air, water, and land. The National Environmental
Research Centers provide this multidisciplinary focus through programs
engaged in
• studies on the effects of environmental contaminants on
man and the biosphere, and
• a search for ways to prevent contamination and to
recycle valuable resources.
In May 1973, the Solid and Hazardous Wastes Research
Laboratory published a manual "Physical, Chemical, and Microbiological
Methods for Solid Waste Testing" (EPA 6700-73-01). It was not intended to
be a complete manual, but the first edition of a growing collection of
methods used to characterize refuse, compost, incinerator residues and
wastewaters, landfill leachates, and related water samples. This publication is
the first manual supplement and presents for the first time procedures for
determining (a) chloride in solid wastes, incinerator wastewaters, landfill
leachates, and related water samples; (b) total phosphate in solid wastes; and
(c) total and orthophosphate in refuse extracts, landfill leachates, and related
water samples.
A. W. Breidenbach, Ph.D.
Director
National Environmental
Research Center, Cincinnati
111
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LABORATORY PROCEDURE FOR DETERMINING THE CHLORIDE
CONTENT OF INCINERATOR WASTEWATERS,
LANDFILL LEACHATES, AND RELATED WATER SAMPLES
Nancy S. Ulmer*
DISCUSSION 2
EQUIPMENT 2
REAGENTS 3
SAFETY PRECAUTIONS 3
STANDARDIZATION 3
SAMPLE PREPARATION 4
PROCEDURE 5
CALCULATIONS 5
METHOD EVALUATION 6
ACKNOWLEDGMENTS 10
REFERENCES 10
•"Research Chemist, Criteria Development Branch, Water Supply Research Laboratory,
National Environmental Research Center - Cincinnati; Miss Ulmer was formerly with
the Solid and Hazardous Waste Research Laboratory of NERC - Cincinnati.
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METHODS OF SOLID WASTE TESTING
DISCUSSION
The significance of chloride ion as a solid waste characteristic becomes apparent when one
considers the impact of the discharge of highly reactive incinerator waters and landfill leachates to
the environment. The direct effect of chloride on the receiving medium is, of course, a chemical
degradation. Indirect effects, biological in nature, may also occur. Thus, a knowledge of the chloride
content of incinerator scrubber, quench, and clarifier wastewaters; landfill leachates; and related
water samples is of value to those persons developing and evaluating water treatment processes in
solid waste management systems.
Chemists have employed a variety of titrimetric, potentiometric, and colonmetric methods for the
determination of chloride in water and wastewater (1,2). The procedure recommended here is a
mercuric nitrate titration. In the pH range of 2.3 to 2.8, diphenylcarbazone indicates the end point of
the titration by forming a deep purple complex with excess mercuric ion. The error in the titration is
about 1 percent of the titrant volume used per change of 0.1 pH unit, in the pH range of 2.1 to 2.8.
EQUIPMENT
1. Balance, analytical, 0.1 -mg readability
2. Bar, magnetic stirring, approximately 14 mm (9/16 inch) long
3. Beakers, Pyrex, 250-ml
4. Blender, e.g., Waring® no. 700
5. Bottles, liquid storage, Pyrex, amber, 1-gal (~ 3.8-hters), with screw-cap lid
6. Bottles, reagent, Pyrex, amber, 500-ml
7. Bottles, reagent, Pyrex, 250-ml and 1-liter
8. Bottle, weighing; low form; cylindrical with standard taper cap; height, 30mm; inside
diameter, 60 mm
9. Buret, 50-ml, with a fine tip, dispensing drops 0.025 ml or less in volume
10. Buret, micro, 5-ml, with a fine tip, dispensing drops 0.01 ml or less in volume
11. Desiccator, either Pyrex or small stainless-steel cabinet-type
12. Filters, cellulose ester, 0.45ju-pore size, 47-mm-diameter (e.g., Millipore Corp. type HA)
13. Filter holders, hydrosol stainless, (e.g., Millipore Corp. no. XX20-047-20)
14. Flasks, filtering, Erlenmeyer form with side arm, 250-ml
15. Flasks, volumetric, 500-ml, l-liter, and 2-liter
16. Meter, pH (e.g., Corning, Model 7 with Corning pH electrode no. 476022 with triple-purpose
glass membrane and Corning reference calomel electrode no. 476002 with asbestos junction; a
silver electrode, Corning no. 476065, is suggested if the chloride concentration of the unknown
solution is low)
17. Pipets, Pyrex, serological, 1-ml and 5-ml
18. Pipets, Pyrex, volumetric, 5-, 10-, 15-, and 20-ml
19. Spatula, stainless-steel (e.g., Scoopula,® Fisher Scientific Co. no. 14-357)
20. Stirrer, magnetic, round (e.g., Fisher Scientific Co. no. 14-511-1)
21. Support, buret
22. Tubing, vacuum (with internal diameter to fit both the side arm of the filtering flask and the
vacuum source)
23. Vacuum source
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Chloride in Solutions
REAGENTS
1. Chloride-free water- If necessary, redistill or deionize distilled water to remove chloride and any
interferring ion, such as iron.
2. Diphenylcarbazone bromphenol blue indicator: Dissolve 2.5 g diphenylcarbazone and 0.25 g
bromphenol blue in 375 ml 95 percent ethyl alcohol and dilute with same to 500 ml. Store in
an amber reagent bottle. (Note: Some analysts employ a diphenylcarbazone indicator
containing xylene cyanol FF (l,p. 98). The author prefers the bromphenol blue indicator
because its color change (at pH 3) serves as a guide in the pH adjustment of the sample prior to
titration, thus, the routine use of a pH meter is eliminated. The final yellow-pink-deep
purple color change is generally easier to discern than the blue-purple change of the indicator
containing xylene cyanol FF).
3. Nitric acid solution, approximately 3.9 N: To 375 ml chloride-free water, slowly add
125 ml concentrated nitric acid. Cool and store in a 1-liter reagent bottle. (Note: Some analysts
recommend a less concentrated nitric acid solution. The use of a 3.9 N acid solution, however,
minimizes the dilution of the sample during pH adjustment.)
4. Standard sodium chloride solution, 0.0141 N: Dissolve 0.8241 g analytical reagent grade
NaCl (previously dried at HOC for 1 hour) in chloride-free water and dilute with same to
1 liter.
5. Standard mercuric acid solution no. 1, (0.1410 N): Dissolve 50 g Hg(NO3)2-H2O in 1800 ml
chloride-free water containing 5 ml concentrated nitric acid. Dilute with chloride-free water to
2 liters. Determine the normality of the solution as directed in the Standardization section of
this Procedure.
6. Standard mercuric nitrate solution no. 2, (0.0141 N): Dissolve 5 g Hg(NO3)2-H2O in 200 ml
chloride-free water containing 0.5 ml concentrated nitric acid, and dilute with chloride-free
water to 2 liters. Determine the normality of the solution as directed in the Standardization
section of this Procedure.
7. Buffer solution, pH 2.0 ± 0.02 at 25 C (e.g., Fisher Scientific Co. no. SO-B-96.)
8. Potassium chloride solution, saturated (e.g., Corning no. 477000).
SAFETY PRECAUTIONS
To avoid hazards associated with the titration
1. Wear safety glasses when handling concentrated nitric acid and mixtures thereof.
2. Exercise care in weighing, transferring, and disposing mercuric nitrate solutions because
inhalation, ingestion, or contact with the compound may cause mercurial poisoning.
STANDARDIZATION
The normality of a mercuric nitrate solution is determined after titrating triplicate samples of
both a water blank and a standard sodium chloride solution, as follows:
Procedure Comments
1. Place 100ml of the sample to be titrated 1. a) If titrating a water blank, use 100ml of
with mercuric nitrate solution in a 250-ml chloride-free water.
beaker. b) If titrating a standard NaCl solution
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METHODS OF SOLID WASTE TESTING
2. While gently stirring the contents of the
beaker with a magnetic stirrer, add 1 ml
diphenylcarbazone bromphenol blue indica-
tor.
3. Slowly add 3.9 N nitric acid dropwise until a
yellow color forms.
4. Using the mercuric nitrate solution that is to
be standardized, titrate the contents of the
beaker to a deep purple end point.
5. Calculate and record the average volume of
titrant required to titrate 100 ml
chloride-free water.
6. Calculate the normality of the mercuric
nitrate solution as directed in the
Calculations section of this Procedure. Aver-
age the calculations.
with mercuric nitrate solution no. 1
(approximately 0.1410 N), use 25 ml
0.0141 N NaCl diluted to 100 ml with
chloride-free water.
c) If titrating a standard NaCl solution
with mercuric nitrate solution no. 2
(approximately 0.0141 N), use 5 ml
0.0141 N NaCl diluted to 100 ml with
chloride-free water.
4. a) Use a 50-ml buret with mercuric nitrate
solution no. 1 and a S-ml micro buret
with mercuric nitrate solution no. 2.
b) The pH of the solution should be
2.5 ± 0.1 at the end point.
5. In our laboratory, 100ml chloride-free
water usually requires 0.02 ml 0.141 ON or
0.2 ml 0.0141 N mercuric nitrate.
6. The deviation of each individual observation
of normality from the average should not
exceed 0.0002.
SAMPLE PREPARATION
Physical
Process or tap water, well water, and other groundwater samples are generally analyzed directly
without any physical preparation; however, landfill leachates containing soil particles are usually
filtered through a Millipore® HA filter using a hydrosol filter holder. In this manner, iron particles,
which can interfere with the titration, can be removed without loss of soluble chloride. Incinerator
quench, scrubber, and clarifier waters containing insoluble particles of various sizes are usually
homogenized in a Waring Blender® prior to analysis. (Filtration of incinerator wastewaters may be
applicable, but has not been evaluated in our laboratory.)
Chemical
If a sample contains more than 10 mg sulfite or chromate or 20 mg ferric ion per liter (even after
dilution with chloride-free water to an appropriate range of chloride concentration), the analyst
should also chemically pretreat the samples as suggested by the American Society for Testing and
Materials in Referee Method A of standard D512-67 (2, p. 26-27).
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Chloride in Solutions
PROCEDURE
Duplicate determinations of a water blank; a standard solution; and an incinerator wastewater, or
landfill leachate, or related water sample will be required. The chloride content of two 100-ml
aliquots of chloride-free water should be determined as outlined in the Standardization section. The
procedure, presented herein, is applicable for the determination of 250 mg (or less) chloride in
100-ml aliquots of a standard or aqueous solution. Smaller aliquots (5 to 50 ml) are generally used to
attain measurable chloride concentrations and to avoid color and ionic interferences during titration.
(See Method Evaluation section of this Procedure.)
Mercuric nitrate solution no. 1 (approximately 0.1410 N) can be used for titrating 100-ml aliquots
containing up to 250 mg chloride. Those aliquots, containing less than 5.0 mg chloride, are best
titrated, however, with mercuric nitrate solution no. 2 (approximately 0.0141 N).
Procedure
1. Place an appropriate aliquot of sample
(100 ml or less) in a 250 ml beaker.
2. Dilute the sample to 100 ml, if necessary,
with chloride-free water.
3. While carefully stirring the contents of the
beaker with a magnetic stirrer, add 1 ml
diphenylcarbazone bromphenol blue indi-
cator.
4. Slowly add 3.9 N nitric acid dropwise until
a yellow color forms.
5. Using the appropriate mercuric nitrate solu-
tion, titrate the contents of the beaker to a
deep purple end point. Record the volume
of titrant used.
Comments
1. The aliquot must contain less than 250 mg
chloride.
5. a) Use mercuric nitrate solution no. 1, con-
tained in a 50-ml buret, for 100-ml sam-
ples containing 5.0 to 250 mg chloride.
b) Use mercuric nitrate solution no. 2, con-
tained in a 5-ml micro buret for 100-ml
samples containing less than 5.0 mg chlo-
ride.
6. Calculate the concentration of chloride as
instructed in the Calculations section im-
mediately below.
CALCULATIONS
The normality, (N), of either mercuric nitrate solution is calculated as follows:
where
N,
V,
A
B
normality of the standard sodium chloride solution
ml of standard sodium chloride solution diluted to 100 ml
ml of mercuric nitrate solution used to titrate the sodium chloride solution
ml of mercuric nitrate solution used to titrate 100 ml chloride-free water.
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METHODS OF SOLID WASTE TESTING
The concentration of chloride (mg Cl/1) in a sample is calculated as follows:
_N(A-.01BC) (35.45) (1000)
where
N = normality of the mercuric nitrate solution used in the titration
A = ml of mercuric nitrate solution used in the titration
B = ml of mercuric nitrate solution used to titrate 1 00 ml of chloride-free water
C = ml of chloride-free water used to dilute the sample aliquot to 1 00 ml
S = ml undiluted sample titrated
METHOD EVALUATION
Interferences
Iodide and bromide are titrated with mercuric nitrate in the same manner as chloride. Zinc, lead,
nickel, ferrous, and chromous ions affect the solution and end point colors but not the accuracy
unless their individual concentrations exceed lOmg per 100-ml sample. Only 5 mg copper can be
tolerated in a similar volume of sample. Interferences will also occur when more than 1 mg of sulfite
or chromate or 2 mg ferric ion is present in a 100-ml sample.
Accuracy
The accuracy of the method was first evaluated by determining the chloride concentration of two
aqueous samples, which were provided by the Analytical Quality Control Laboratory, National
Environmental Research Center-Cincinnati, U.S. Environmental Protection Agency. The average
percent recovery of the chloride concentration of these samples was 100. (See Table 1 .) The chloride
content of 1 0-ml aliquots of 13 wastewater samples was also determined before and after adding 5 ml
0.0141 N NaCl. The percent chloride recovery from the Winston Salem, North Carolina, and Boone
County, Kentucky, landfill leachates was 96.8 and 1 00, respectively. The average percent chloride
recovery from the 1 1 Boone County, Kentucky, refuse extracts was 97.9.
Precision
The reproducibility of the observations of the chloride content of incinerator tap water and
wastewater samples has been evaluated by calculating the standard deviation and coefficient of
variation of the triplicate determinations of each of 20 samples (see Table 2). In each case, the
coefficient of variation was 0.02 or less.
The reproducibility of the observations of the chloride content of the refuse extracts, landfill
leachates, and related well-water samples was evaluated by calculating the pooled standard deviation
and coefficient of variation of groups of duplicate observations. The groupings were based on sample
type, and the subgroupings on range of chloride concentration. A review of the data, presented in
Table 3, similarly reveals that the coefficient of variation never exceeded 0.02.
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TABLE 1
ACCURACY OF THE METHOD
Chloride in Solutions
Sample type
Sample source
Lab. No.
% Recovery of added
chloride
Aqueous solutions
Analytical
Quality Control
Min. 1
Min. 2
100
100.1
Landfill leachates
Refuse extracts
Lab. (NERC-
Cincinnati, U.S.
EPA)
Winston Salem,
N.C.
Boone County, Ky.
(Cell 2D)
Boone County, Ky.
(Cell 1)
70-204
73-8
71-120
71-173
71-125
71-128
71-130
71-133
71-135
71-138
71-140
71-145
71-160
96.8
100
96.4
96.4
98.0
96.8
100.4
96.4
96.8
100.4
97.6
97.6
100
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METHODS OF SOLID WASTE TESTING
TABLE 2
PRECISION OF TRIPLICATE CHLORIDE DETERMINATIONS OF
WATER SAMPLES FROM INCINERATOR NO. 3, DELAWARE CO , PENNSYLVANIA
Type of
sample
Tap or process
water
Quench water
Scrubber water
Clarifier
water
Lab. No.
70-56
70-64
70-72
70-80
70-88
70-54
70-62
70-70
70-78
70-86
70-52
70-60
70-68
70-76
70-84
70-50
70-58
70-66
70-74
70-82
Observed mean,
mgCl/1
(M)
63.83
83.68
75.05
87.48
88.16
512.4
1045
1169
729.8
780.5
1399
1606
1816
1868
2573
1348
1386
1621
1683
2345
Standard
deviation
(S)
1.20
0.30
1.36
0.52
1.50
1.38
2.30
2.65
1.79
1.79
1.15
0.00
1.73
3.46
2.87
1.15
1.53
0.00
0.60
2.65
Coefficient of
variation
(S/M)
0.02
0.00
0.02
0.01
0.02
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
8
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Chloride in Solutions
TABLE 3
PRECISION OF DUPLICATE CHLORIDE DETERMINATIONS OF REFUSE EXTRACTS
LEACHATES, AND WELL-WATER SAMPLES FROM THE RESEARCH LANDFILL OPERATION
IN BOONE COUNTY, KENTUCKY
Type of
sample
Refuse
extracts*
Leachates
Leachates
Sample
source
Cell no. 1
refuse
Cell no. 1
upper
pipe
Cell no. 1
lower
pipe
Group
Total
Subgroup A
Subgroup B
Subgroup C
Total
Subgroup A
Subgroup B
Subgroup C
Total
No. of
samples
in
group
14
1
11
2
48
1
44
3
38
Range of chloride
concentration
in me/1
(»
1
1
10
100
10
10
100
1000
100
(<)
1000
10
100
1000
10000
100
1000
10000
1000
... Pooled
Mean . . .
_., „ standard
mgCl/1 ,
deviation
(M)
64.86
5.90
52.74
161.0
694.8
90.00
678.8
1123.
495.8
(Sp)
0.39
0.14
0.39
0.50
4.35
0.00
4.01
8.16
3.95
•
Coefficient
of variation
(Sp/M)
0.01
0.02
0.01
0.00
0.01
0.00
0.01
0.01
0.01
Well water Well no. 1
Total
Subgroup A
Subgroup B
Subgroup C
18
3
7
8
10
10
100
1000
10000
100
1000
10000
1621.
83.93
417.0
3619.
7.74
0.40
4.31
10.89
0.00
0.00
0.01
0.00
Well water
Well no. 2A Total
Subgroup A
Subgroup B
20
14
6
1000
1000
10000
100000
10000
100000
8458.
3936.
16800.
15.04
7.07
31.62
0.00
0.00
0.00
*Each extract was prepared in the laboratory by suspending 50 g ground, mixed refuse (particles 2 mm or less in
diameter) in 750 ml distilled water. After occasional stirring over a 15-hour penod, the mixture was filtered. The
remaining solid was washed with several 200-ml portions of distilled water and the mixture refiltered each time. The
combined filtrates were diluted to 2 liters with distilled water.
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METHODS OF SOLID WASTE TESTING
ACKNOWLEDGMENTS
The author wishes to thank the staffs of the Process and Disposal Division, Office of Solid Waste
Management Programs, and the Landfill Disposal Project, Solid and Hazardous Waste Research
Laboratory, NERC-Cincinnati, for supplying the incinerator and landfill water samples, respectively.
Special thanks are also extended to Israel Cohen, Monitoring and Analysis Project, for preparing
some of the incinerator water samples.
REFERENCES
1. American Public Health Association, American Water Works Association, and Water Pollution
Control Federation. Chloride. In: Standard methods for the examination of water and
wastewater. 13th ed. Washington, D. C., American Public Health Association, 1971. p. 95-99,
376-380.
2. American Society for Testing and Materials. Standard methods of test for chloride ion in
industrial water and wastewater. In: 1969 Book of ASTM standards, pt. 23. D512-67.
Philadelphia, 1969. p. 24-31.
10
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LABORATORY PROCEDURE FOR DETERMINING
THE CHLORIDE CONTENT
OF SOLID WASTES
Nancy S. Ulmer*
DISCUSSION 2
EQUIPMENT 2
REAGENTS 3
SAFETY PRECAUTIONS 4
STANDARDIZATION 5
SOLID WASTE SAMPLE PREPARATION 5
PROCEDURE 5
CALCULATIONS 9
METHOD EVALUATION 10
ACKNOWLEDGMENTS 10
REFERENCES 12
*Research Chemist, Criteria Development Branch, Water Supply Research Laboratory,
National Environmental Research Center — Cincinnati; Miss Ulmer was formerly with
the Solid and Hazardous Waste Research Laboratory of NERC-dncinnati.
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METHODS OF SOLID WASTE TESTING
DISCUSSION
The significance of chloride ion as a solid waste characteristic becomes apparent when one
considers the impact it may have upon processing equipment and on the environment surrounding a
processing or disposal site. P. D. Miller et al. have studied the corrosion, pitting, and cracking of
incinerator boiler tubes, probes, and wet scrubbers (1). Their analyses clearly demonstrated the
presence of ferrous chloride (FeCl2), sodium chloride (NaCl), and potassium chloride (KC1) in
boiler-tube deposits and up to 16 percent chloride in the scrubber fan deposits. Their investigations
also revealed that the most corrosive salts at 600 F (~316 C) are potassium bisulfate (KHSO4) and
potassium pyrosulfate (K2S2O7), whereas at 800 to 1000 F (~427 to 538 C) zinc chloride (ZnCl2)
and lead chloride (PbCl2 ) accelerate the corrosion. Since chloride appears to enhance the corrosive
action of sulfates, a knowledge of the concentration and distribution of chloride in solid wastes is
important to the engineers and scientists responsible for the design, maintenance, and control of
incinerator equipment.
The emission of hydrogen chloride gas from incinerator stacks and the leaching of highly reactive
chloride ion from municipal refuse and residue in incinerators or landfills may result in
environmental pollution. The direct effect of chloride is, or course, a chemical degradation of the
receiving medium, but indirect effects, biological in nature, may also occur. Thus, a knowledge of the
chloride content of municipal refuse, incinerator residue, wastewaters, stack emissions, and landfill
leachates is also important to those persons developing and evaluating gaseous pollutant control
measures and water treatment processes in solid waste management systems.
Chemists have employed a variety of analytical procedures to determine the chloride content of
the individual components of solid wastes (2-13). Most of the methods recommend that first a
sample be oxidized by either (a) wet digestion or (b) combustion in a muffle furnace, Parr Bomb, or
Schoniger, Thompson-Oakdale, or similar glass apparatus. A potentiometric, titrimetric, or
gravimetric determination of the chloride content then follows after absorption and solution of the
products of oxidation.
Since paper is the primary component of solid wastes, the ASTM procedure for chloride in paper
was considered (7). Briefly, it consists of ashing a dried sample at 600 C in a muffle furnace. After
aqueous solution and dilution of the ash, the chloride content is determined by titration using
AgNO3 as titrant and K2Cr2O7 as indicator. Since the sensitivity of this procedure is limited to 150
ppm (0.15 mg Cl/g sample) however, the technique is not applicable to solid wastes.
The procedure presented here, developed and evaluated in the Solid and Hazardous Waste
Research Laboratory, represents a modification of the techniques used for the determination of
chloride in mineral oils (14), epoxy resins (15), and wastewater (16). Briefly, it recommends that a
0.25- to 0.5-g solid waste sample, layered with mineral oil, be combusted under 30 atmospheres O2
in a combustion cup suspended in a Parr Bomb that contains a carbonate solution. The products of
combustion are absorbed by or dissolved in the carbonate solution, transferred with rinsing to a
beaker, diluted to 200 ml with distilled water, treated with diphenylcarbazone bromphenol blue
indicator, and acidified with dilute1 nitric acid until a yellow color (pH 3.0) forms. The chloride
content is then determined by titrating with 0.0141 N mercuric nitrate until excess mercuric ions are
indicated by the formation of a deep purple color (pH 2.5 ± 0.1).
EQUIPMENT
1. Balance, analytical, 0.1 -mg read ability
2. Bar, magnetic stirring, approximately 14 mm (9/16 inch) long
3. Beakers, Pyrex, 600-ml
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Chloride in Solids
4. Bottle, liquid storage, Pyrex, amber, 1-gal (3.8-liters), with screw-cap lid
5. Bottle, reagent, Pyrex, amber, 500-ml
6. Bottles, reagent, Pyrex, 1-liter
7. Bottle, washing-dispensing, polyethylene, 500-ml
8. Bottle, weighing; low form; cylindrical with standard taper cap, height, 30 mm; inside diameter,
60 mm
9. Buret, 25-ml, with fine tip, dispensing drops 0.025 ml (or less) in volume
10. Calorimeter, Parr Adiabatic, Series 1200; with a self-sealing, 360-ml stainless-steel, oxygen bomb
with double valve (Parr no. 1101); an oxygen-filling connection (Parr no. 1823); stainless-steel
capsules (Parr no. 43AS); and 26-gauge platinum fusion wire (Parr no. 43A); a platinum-lined or
tantalum-lined bomb and nickel capsules are suggested if numerous determinations are to be
performed over a long period of time.
11. Cloth, aluminum oxide, fine (e.g., Norton Alox®cloth, no. 120 or 150)
12. Cylinder, graduate, Pyrex, 25-ml
13. Desiccator, either Pyrex or small stainless-steel cabinet-type
14. Dishes, aluminum, moisture, 89- x 50-mm, with tightly fitting lids (e.g., Arthur H. Thomas Co.,
no. 3840-F30)
15. Flasks, volumetric, Pyrex, 2-liter, 1-liter, and 500-ml
16. Forceps, dissecting, with straight sharp points (e.g., Fisher Scientific Co., no. 8-880)
17. Meter, pH (e.g., Corning, Model 7, with Corning pH electrode no. 476022 with triple-purpose
glass membrane and Corning reference calomel electrode no. 476002 with asbestos junction; a
silver electrode, Corning no. 476065, is suggested if the chloride concentration of the unknown
solution is low)
18. Oven, forced draft, capable of maintaining a set temperature within the 75- to 105-C range over
a 4-hour period (e.g., Precision Scientific Co., Model 18)
19. Pipets, Pyrex, serological, 1-ml and 5-ml
20. Policemen, rubber, for glass rods, 4.8 mm (3/16 inch) in diameter
21. Press, pellet, with a 12- to 19-mm-(l/2- to 3/4-inch) diameter punch and dye set (e.g., Parr press
no. 2811 with punch and dye set no. A33PR or Carver Lab Press, Model B, and a
19-mm-diameter punch and dye set, made in machine stop)
22. Rods, stirring, glass, 4.8 mm (3/16 inch) in diameter
23. Spatula, stainless-steel (e.g., Scoopula,® Fisher Scientific Co. no. 14-357)
24. Stirrer, magnetic, round (e.g., Fisher Scientific Co. no. 14-511-1)
25. Support, buret
26. Support, gas cylinder, safety (e.g., Fisher Scientific Co. no. 10-595)
27. Support, ringstand, with a cast-iron support ring having a 60-mm (2-3/8 inch) I.D.
28. Syringe, Luer, Tuberculin, Pyrex, 1-ml, with 1/100-ml subdivisions
29. Wool, steel, fine (gauge no. 0000)
30. Wrench, for opening hand wheel on oxygen tank
REAGENTS
1. p-Chlorobenzoic acid, M. P. 239-241 C, 22.64 percent chloride by weight: Dry the solid at
105 C for 1 hour and store in a desiccator until used as a standard in the evaluation of the entire
procedure.
2. Squibb mineral oil, extra heavy
3. Chloride-free water: If necessary, redistill or deionize distilled water to remove chloride and any
interferring ion, such as iron.
-------
METHODS OF SOLID WASTE TESTING
4. Sodium carbonate solution, 2 percent: Dissolve 40 g anhydrous Na2CO3 in chloride-free water
and dilute with same to 2 liters. Store in two 1-liter reagent bottles.
5. Oxygen, produced by rectification of air, cylinder size 1A (244 cu. ft.)
6. Nitric acid solution, approximately 3.9 N: To 375 ml chloride-free water, slowly add 125 ml
concentrated nitric acid. Cool and store in a l-liter reagent bottle. (Note: Other procedures
recommend a less concentrated nitric acid. The use of a 3.9 N acid solution will, however,
minimize sample dilution during pH adjustment.)
7. Diphenylcarbazone bromphenol blue indicator: Dissolve 2.5 g diphenylcarbazone and 0.25 g
bromphenol blue in 375 ml of 95 percent ethyl alcohol and dilute with same to 500 ml. Store in
an amber reagent bottle. (Note: Some analysts employ an indicator containing 0.25 g
s-diphenylcarbazone and 0.03 g xylene cyanol FF in 100 ml of 95 percent ethyl alcohol. The
author prefers the indicator with bromphenol blue because the color change (at pH 3) serves as
a guide in the pH adjustment of the sample before titration; thus, the routine use of a pH meter
is eliminated. The final yellow-pink-deep purple color change (during the titration) is generally
easier to discern than the blue-purple change of the indicator containing xylene-cyanol FF).
8. Standard sodium chloride solution, 0.0141 N: Dissolve 0.8241 g analytical reagent grade NaCl
(previously dried at 140 C for 1 hour) in chloride-free water and dilute with same to 1 liter.
9. Standard mercuric nitrate solution, 0.0141 N: Dissolve 5g Hg(NO3)2.H2O in 200 ml
chloride-free water containing 0.5 ml concentrated HNO3, and dilute with chloride-free water
to 2 liters. Store in a 1-gal amber bottle. Determine the normality of the solution as directed in
the Standardization section of this Procedure.
10. Buffer solution, pH 2.0 ± 0.02 at 25 C (e.g., Fisher Scientific Co., no. SO-B-96).
11. Potassium chloride solution, saturated (e.g., Corning No. 477000).
SAFETY PRECAUTIONS
The high pressure and explosive reaction employed in the combustion of the sample need not be
hazardous if the analyst observes the following precautions:
1. Limit the total sample weight (solid waste plus oil) to 1 g; i.e., do not use a quantity of sample
that will liberate more than 10,000 calories of heat. If the calorific value of a solid waste is
unknown, determine the value before proceeding with the chloride determination.
2. Do not charge the bomb with more than 30 atmospheres of oxygen. If overcharging occurs,
release the bomb pressure gently and recharge. Never fire an overcharged bomb.
3. Keep all parts of the bomb, especially the insulated electrode assembly, clean and in good
repair. Do not fire a bomb if gas is leaking from the bomb when submerged in water.
4. Stand away from the calorimeter during and immediately after (15 seconds) firing the bomb.
To avoid the chemical hazards associated with the titration:
1. Wear safety glasses when handling concentrated nitric acid and mixtures thereof.
2. Exercise care in weighing, transferring, and disposing mercuric nitrate solutions because
inhalation, ingestion, or contact with the compound may cause mercurial poisoning.
-------
Chloride in Solids
STANDARDIZATION
The normality of the mercuric nitrate solution is determined after titrating triplicate samples of
both a water blank and a standard NaCl solution as follows:
Procedure
1. Place 200 ml of the sample to be titrated
with mercuric nitrate solution in a 600-ml
beaker.
2. While gently stirring the solution with a
magnetic stirrer, add 1 ml of the diphenyl-
carbazone bromphenol blue indicator.
3. Slowly add 3.9 N nitric acid dropwise until a
yellow color forms.
4. Using the mercuric nitrate solution, titrate
the contents of the beaker to a purple end
point. Record the volume of titrant used.
5. Calculate and record the average volume of
titrant required to titrate 200 ml chlonde-
free water.
6. Calculate the normality of the mercuric
nitrate solution as directed in the Calcula-
tions section of this Procedure. Average the
three calculations.
Comments
1. a) Use 200 ml of chloride-free water fora
water blank.
b) For the standard solution, use 5 ml stock
0.0141 N NaCl solution diluted to
200 ml with chloride-free water.
4. The pH of the solution should be 2.5 ± 0.1
at the end point.
5. In our laboratory, this volume is usually
0.04 ml.
6. The deviation of each individual observation
of normality from the average should not
exceed 0.0002.
SOLID WASTE SAMPLE PREPARATION
A solid waste sample must undergo physical preparation before its characterization is initiated in
the laboratory. The sample must be dried to constant weight, preferably in a forced-air or
mechanically-convected oven. A temperature of 70 to 75 C should be used to dry municipal refuse or
compost; incinerator residue may be dried at 100 to 105 C. The particle size of the dried sample
should then be reduced to 0.5 mm (or less) using a hammermill, pulverizer, and laboratory mill. Since
samples may absorb moisture during the grinding and mixing process, they should be redried for 4
hours at the previously specified temperature and then stored in a desiccator.
Immediately before initiating an analysis, prepare several 1.0-g pellets of the standard or solid
waste sample. (A punch and dye set, 12 to 19 mm in diameter, can be used with a Model B, Carver
Laboratory Press, capable of exerting a 7000-lb or 3175 kg load). Store the pellets in a desiccator and
remove as required for the determinations.
PROCEDURE
Duplicate determinations of a water blank, an oil blank, and a standard or solid waste sample will
be required. The volume of mercuric nitrate solution required to titrate two 200-ml aliquots of
-------
METHODS OF SOLID WASTE TESTING
chloride-free water should be determined, as outlined in the Standardization section, steps 1-5. The
chloride content of the oil blank and the standard or solid waste sample should be determined as
follows:
1.
2.
5.
6.
7.
Procedure
Carefully weigh a steel combustion capsule
to the nearest 0.0001 g.
If performing a standard or solid waste
analysis, add an appropriate portion of a
pelletized sample to the capsule and then
proceed to step 3.
Weigh the capsule and solid sample to the
nearest 0.0001 g. Determine and record the
weight of the solid sample.
Using a 1-ml, Pryex, Tuberculin syringe,
flow approximately 0.5 to 0.7 ml extra
heavy Squibb mineral oil directly into the
capsule, wetting any solid sample present.
Weigh the capsule and sample(s) to the
nearest 0.0001 g. Determine and record the
weight of the oil.
Rinse the inner surfaces of the stainless-steel
bomb with the 2 percent Na2 CO3 solution.
Place 25ml fresh 2 percent Na2CO3 solu-
tion in the bomb cylinder.
8. Attach the fuse wire to the 4A and 5A
electrodes of the bomb head.
9. Place the capsule containing the sample in
the base of the 5 A electrode.
10. Bend the fuse wire loop so that it either
barely touches the oil-soaked pellet or lies
just above the free oil (e.g., in the blank).
11. Place the bomb head in the cylinder.
12. Screw the bomb cap down thoroughly by
hand.
Comments
1. a) A capsule should have been previously
cleaned with fine steel wool, then rinsed
with chloride-free water, dried, and
stored in a desiccator until used.
b) Use nickel capsules if many chloride
determinations are planned over a period
of time.
2. a) Use 0.015 to 0.020 g p-chlorobenzoic
acid (standard) or 0.25 to 0.50 g solid
waste.
b) If performing an oil blank analysis, omit
steps 2 and 3 and proceed directly to
step 4.
4. If performing a standard or solid waste
analysis, limit the total weight of the sample
plus oil to 1 g; i.e., do not use sample and oil
quantities that will liberate more than
10,000 calories of heat.
6. a) Use 25 ml of solution for the bomb
cylinder and 15 ml for the bomb head.
b) Support the rinsed bomb head on a ring
stand.
8. Detailed instructions are provided in the Parr
Instrument Company Manual (17).
11. a)
Keep the cylinder upright to prevent any
sample loss from the capsule.
Make sure the sealing ring is in good
condition.
12. The outlet needle valve should be open
dunng this step.
b)
-------
Chloride in Solids
13. Close the outlet needle valve.
14. Remove the inlet valve thumb nut.
15. Attach the union nut of the oxygen-filling
tube firmly by hand.
16. Open the oxygen-filling connection control
valve slowly.
17. Allow the oxygen pressure to rise slowly
until the gauge reads 30 atmospheres.
18. Close the oxygen-filling connection control
valve.
19. Push the ball knob under the relief knob
sideways.
20. Disconnect the oxygen-filling tube.
21. Replace the thumb nut in the inlet valve.
22. Place the bomb in the bucket so that its feet
span the boss at the bottom of the bucket.
23. Attach the thrust terminal to the bomb
head.
24. Lower the bucket into the jacket.
25. Add 2000ml distilled water, at room
temperature, to the bucket.
26. Swing the calorimeter cover to the right and
lower it using the cam lever.
27. Check to see if the pump and stirrer drive
shafts are seated properly.
28. With the water inlet tube attached to a cold
water source and the discharge tube draining
to a sink, open the appropriate valves and
turn on the cold water.
29. After the water begins to drain from the
discharge tube, start the stirring motor.
30. WHILE STANDING TO THE SIDE OF THE
CALORIMETER, press the ignition button.
15. a) Use Parr no. 1823 oxygen-filling
connection.
b) Detailed instructions are provided in the
Parr Instrument Company manual (17,
p. 20-22).
16. a) The oxygen tank valve must have been
opened previously with a special wrench.
b) If the oxygen-filling connection valve is
opened too quickly, some of the sample
may be blown from the capsule and,
thus, prevent complete combustion.
19. This relieves the gas pressure in the con-
necting tube.
23. The lead wire should not extend above the
bucket.
24. Position the bucket so that the stirrer and
handle are in the rear.
27. a)
b)
The pump and stirrer shafts should be
lowered as far as possible and the pulleys
should move freely.
The calorimeter's thermometers are not
used in this test and can be removed.
28. Excessive water pressure will cause seepage
through the stirring shaft journal into the
bucket chamber.
30. a) If ignition occurs, a red light near the
ignition button will flash on briefly.
b) If ignition fails to occur (no red light
seen), proceed immediately to steps
32-35, 38-40, and then begin the deter-
mination again at step 8.
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METHODS OF SOLID WASTE TESTING
31. Allow the bomb to stand in the calorimeter
for 10 minutes after ignition.
32. Turn off the stirring motor and allow the
water to drain from the calorimeter cover.
33. Lift the cam lever, then the calorimeter
cover, and swing the latter to the left.
34. Lift the bucket out of the jacket and
disconnect the thrust terminal wire.
35. Remove the bomb and gently dry the
exterior with a towel.
36. Tilt the bomb 75 to 80 degrees and rotate to
wash the inner surfaces with the Na2CO3
solution.
37. Stand the bomb upright on a table for 10
minutes to allow the Na2CO3 solution to
dram to the bottom of the cylinder.
38. Gently and slowly open the outlet needle
valve to relieve the pressure.
39. Remove the screw cap.
40. Lift the bomb head and capsule slowly from
the cylinder.
41. Inspect the capsule and cylinder for un-
combusted sample.
42. Inspect the inner bomb head surface for
formation of iron oxide.
43. Wash all interior bomb surfaces and all
capsule surfaces with a fine stream of
chloride-free water. Collect all washings in a
600-ml beaker.
44. While gently stirring the combined washings
in the beaker, add 1.0 ml diphenylcarbazone
bromphenol blue indicator.
45. Slowly add 3.9 N nitric acid dropwise until a
yellow color forms.
46. Using 0.0141 N mercuric nitrate, contained
in a 25-ml buret with a fine tip, titrate the
contents of the beaker to a deep purple end
point. Record the volume of titrant used.
47. Calculate the concentration of chloride as
instructed in the Calculations section of this
Procedure.
32. The flow from the discharge tube will return
to normal when the cover is drained.
40. If the capsule fell down into the cylinder
during step 36, do not remove it until step
43.
41. If the combustion was-incomplete, discard
the test and proceed to step 48. Repeat the
determination beginning at step 1.
42. If a red color is noticeable, the analyst
should suspect a high cloride concentration.
The test may have to be repeated with a
smaller sample.
43. a) A rubber policeman is useful in rinsing
the surfaces of the cylinder.
b) The total volume of all washings should
be 200 ml.
44. Use a magnetic stirring device.
46. a) The buret should deliver 0.025-ml drops.
b) The pH of the solution should be
2.5 ±0.1 at the end point.
-------
Chloride in Solids
48. Rinse the interior surface of the bomb head 48. a) Occasionally clean the inner surfaces of
and cylinder with additional chloride-free the bomb head with fine steel wool
water and set them aside to drain. (gauge no. 0000) and then rinse with
chloride-free water and place in a ring
stand support to drain.
b) If the inner surface of the stainless-steel
cylinder becomes pitted over a period of
time, clean the surface with a fine
aluminum cloth (e.g., Alox®cloth no
120 or 150). Rinse surface well with
chloride-free water and drain.
49. For each determination, repeat steps 1-48.
50. At the end of a day (or a series of
determinations), turn off the cold water.
CALCULATIONS
The normality (N) of the mercuric nitrate solution is calculated as follows:
" A-B
where
N, = normality of the standard sodium chloride solution
V, = ml of standard sodium chloride solution diluted to 200 ml
A = ml of mercuric nitrate solution used to titrate the sodium chloride solution
B = ml of mercuric nitrate solution used to titrate 200 ml chloride-free water
The percent chloride (%C10) in the oil blank sample is calculated as follows:
a r, - 100 (N)(C-B) (0.03545)
/O \-r\Q \\r
W0
where
N = normality of the mercuric nitrate solution
B = ml of mercuric nitrate solution used to titrate 200 ml of chloride-free water
C = ml of mercuric nitrate solution used to titrate the total washings from the combusted
oil sample
W0 = grams of oil sample used in this test
The percent chloride (% Cls) of a standard or solid waste sample is calculated as follows:
^ 100 N (D-B) (0.03545) - % C10 (W0)
Ws
where
N = normality of the mercuric nitrate solution
B = ml of mercuric nitrate solution used to titrate 200 ml of chloride-free water
D = ml of mercuric nitrate used to titrate the total washings from the combined oil and
standard or solid waste sample
% C10 = percent chloride in the oil
W0 = grams of oil used in the test
Ws = grams of standard or solid waste used in the test
-------
METHODS OF SOLID WASTE TESTING
METHOD EVALUATION
Interferences
Iodide and bromide are titrated with mercuric nitrate in the same manner as chloride. Chromate
and sulfite ions interfere when present in excess of 10 mg/1 (16, p. 97-98). Concentrations of ferric
ions up to 20 mg/1 can usually be tolerated. Above that level, ferric ions interfere with the indicator
and cause a sliding or delayed endpoint in the titration.
Accuracy
Five p-chlorobenzoic acid samples, ranging in weight from 12 to 25 mgand containing 3 to 6 mg
chloride, respectively, were analyzed by using this procedure. The mean percent recovery of the
theoretical chloride content was 98.1. Three aliquots of a Boone County, Kentucky, refuse sample
(no. 71-130) were also analyzed before and after the addition of 15 to 23 mg p-chlorobenzoic acid.
The mean percent recovery of the added chloride was 97.4.
Precision
The reproducibility of the method has been determined by calculating the standard deviation of
the replicate determinations of the chloride content of a number of refuse samples. The data are
presented in Table 1.
ACKNOWLEDGMENTS
The author wishes to thank Dirk Brunner and the staff of the Landfill Disposal Project for
providing the Boone County, Kentucky, refuse samples. Special thanks are extended to Israel Cohen,
Monitoring and Analysis Project, for preparing these samples.
Raymond Loebker, Thermal Degradation Project, kindly provided and prepared the Troy, Ohio,
refuse samples for analyses.
10
-------
Chloride in Solids
TABLE I
REPRODUCIBILITY OF THE METHOD
Source of
refuse sample
Boone County,
Kentucky
Troy, Ohio
Lab. No.
71-120
71-123
71-125
71-128
71-130
71-133
71-135
71-138
71-140
71-142
71-145
71-155
71-158
71-160
72-668
72-669
72-670
72-671
72-672
73-19
73-20
Number of
replicate
determinations
per sample
2
2
2
2
2
2
2
2
2
2
2
2
2
2
3
2
6
2
2
2
2
Observed
mean
%
chloride
0.43
4.48
0.28
0.12
0.29
1.16
0.25
0.36
0.30
0.20
0.62
0.92
0.76
0.49
0.54
0.44
0.78
0.70
0.32
0.37
0.38
Standard
deviation
0.01
0.17
0.03
0.03
0.01
0.01
0.00
0.01
0.03
0.03
0.02
0.03
0.03
0.01
0.04
0.01
0.02
0.01
0.04
0.01
0.01
11
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METHODS OF SOLID WASTE TESTING
REFERENCES
1. Miller, P. D., et al. Corrosion studies in municipal incinerators. A report prepared for the Solid
Waste Research Laboratory under Research Grants EP-00325 and EP-00325-S1. Cincinnati,
National Environmental Research Center, Office of Research and Monitoring, U.S.
Environmental Protection Agency, 1972. 120 p.
2. Horwitz, W., ed. Cereal foods: macaroni, egg noodles, and similar products. In: Official methods
of the Association of Official Analytical Chemists, llth ed. sect. 14.129. Washington, D.C.,
Association of Official Analytical Chemists, 1970. p. 230.
3. Horwitz, W., ed. Plants. In: Official methods of the Association of Official Analytical Chemists.
11th ed. sect. 3.067-3.072. Washington, D.C., Association of Official Analytical Chemists, 1970.
p. 45.
4. Horwitz, W., ed. Fish and other marine products. In: Official methods of the Association of
Official Analytical Chemists, llth ed. sect. 18.014-18.015. Washington, D.C., Association of
Official Analytical Chemists, 1970. p. 296.
5. Horwitz, W., ed. Meats and meat products. In: Official methods of the Association of Official
Analytical Chemists. 11th ed. sect. 24.038. Washington, D.C., Association of Official Analytical
Chemists, 1970. p. 398.
6. Steyermark, A., R. A. Lalancute, and E. M. Contereas. Collaborative study of microanalytical
determination of bromine and chlorine by oxygen flask combustion. Journal Association Official
Analytical Chemists, 55(4):680-683, 1972.
7. American Society for Testing and Materials. Standard method of test for total chloride content
of paper and paper products. In: 1969 book of ASTM standards, pt. 15. Dl 161-60. sect. 1-9.
Philadelphia, 1969. p. 416-419.
8. American Society for Testing and Materials. Standard method of test for chlorine in cellulose. In:
1960 book of ASTM standards, pt. 15. D2641-67T. sect. 1-13. Philadelphia, 1969. p. 814-816.
9. Colman, D. M., Determination of chlorine concentration in plastics. University of California
method 5346. Livermore, California, University of California, 1958. p. 3-5.
10. American Society for Testing and Materials. Standard method of test for total chlorine in vinyl
chloride polymers and copolymers. In: 1969 book of ASTM standards, pt. 27. D1303-55. sect.
1-9. Philadelphia, 1969. p. 486-488.
11. American Society for Testing and Materials. Standard method of test for chloride content in
polyvinylchloride polymers and copolymers used in surface coatings. In: 1969 book of ASTM
standards, pt. 20. Dl 156-52. sect. 1-6. Philadelphia, 1969. p. 540-542.
12. American Society for Testing and Materials. Standard method of test for chlorine in organic
compounds by sodium peroxide bomb ignition. In: 1969 book of ASTM standards, pt. 22.
E256-67. sect. 1-8. Philadelphia, 1969. p. 586-592.
13. American Society for Testing and Materials. Standard method of test for chlorine in new and
used petroleum products (bomb method). In: 1969 book of ASTM standards, pt. 17. D808-63.
sect. 1-7. Philadelphia, 1969. p. 232-235.
14. Agruss, M. S., G. W. Ayers, Jr., and H. Schindler. Organic halogen compounds in mineral oils.
Industrial and Engineering Chemistry, 13(2):69-70, 1941.
15. American Society for Testing and Materials. Standard method of test for total chlorine content
of epoxy resins. In: 1969 book of ASTM standards, pt. 20. D1847-67. sect. 1-8. Philadelphia,
1969, p. 864-866.
12
-------
Chloride in Solids
16. American Public Health Association, American Water Works Association, and Water Pollution
Control Federation. Chloride. In: Standard methods for the examination of water and
wastewater. 13th ed. Washington, D.C., American Public Health Association, 1971. p. 97-99.
17. Parr Instrument Company. Oxygen bomb calorimetry and combustion methods. Technical
Manual no. 130. Moline, Illinois, 1966. 56 p.
13
-------
LABORATORY PROCEDURE FOR DETERMINING THE
TOTAL PHOSPHATE AND TOTAL ORTHOPHOSPHATE
CONTENTS OF REFUSE EXTRACTS, LANDFILL
LEACHATES, AND RELATED WATER SAMPLES
Nancy S. Ulmer*
DISCUSSION 2
SAFETY PRECAUTIONS 2
EQUIPMENT 3
REAGENTS 3
STANDARDIZATION 4
SAMPLE PREPARATION 5
PROCEDURES 5
Determination of Total Phosphate 5
Determination of Total Orthophosphate 7
CALCULATIONS 8
METHOD EVALUATION 9
ACKNOWLEDGMENTS 10
REFERENCES 12
*Research Chemist, Criteria Development Branch, Water Supply Research Laboratory,
National Environmental Research Center-Cincinnati; Miss Ulmer was formerly with the
Solid and Hazardous Waste Research Laboratory of NERC-Cmcinnati
-------
METHODS OF SOLID WASTE TESTING
DISCUSSION
Orthophosphates, condensed (pyro-, meta-, and poly-) phosphates, and organically-bound
phosphorus may occur in natural water and wastewaters. Since phosphorus promotes the growth of
algae, its discharge into receiving streams may contribute to the deterioration of water quality and
the eutrophication of lakes. A knowledge of the form and concentration of phosphorus in solid waste
leachates and other water samples, associated with landfill operations, is therefore important to the
scientists and engineers responsible for developing and evaluating solid waste and water quality
management systems.
Chemists have employed numerous methods to determine the various phosphorus forms present in
water and wastewater (1-10). In general, the procedures are characterized by (1) a conversion of the
phosphorus forms of interest to orthophosphate and (2),the determination of the latter by
colonmetnc, gravimetric, or atomic absorption techniques.
The amino reduction method (2 [sect. 13-21, p. 46-50]; 11) is recommended here for the
determination of the orthophosphate content of water and wastewater samples. An aliquot of an
unfiltered but appropriately diluted sample is first treated with a sulfuric acid reagent containing
bismuth. Ammonium molybdate is then added to form molybdophosphate. The subsequent addition
of l-amino-2-naphthol-4-sulfomc acid results in the formation of molybdenum blue. The absorbance
of the latter is measured at 650 nm against the absorbance of a similarly treated distilled water blank.
The bismuth in the acid reagent increases the intensity of the blue color fourfold.
When a total phosphate determination is desired, an unfiltered but appropriately diluted sample,
contained in an Erlenmeyer flask, is similarly treated with the sulfuric acid bismuth reagent. After
the addition of potassium persulfate, the sample is heated to convert the condensed phosphates and
organically-bound phosphorus to orthophosphate. The molybdenum blue color of the cooled and
appropriately diluted digest is then developed after the addition of ammonium molybdate and amino
solutions as previously described. The absorbance of the solution is measured against that of a
similarly processed distilled water blank. The observed total orthophosphate concentration serves as a
measurement of the total phosphate.
SAFETY PRECAUTIONS
To avoid hazards associated with the maintenance of the glassware and the performance of each
analysis:
1. Wear safety glasses when handling concentrated acids or mixtures thereof.
2. Perform all acid digestions in a hood to avoid inhaling acid fumes.
3. Wear asbestos glove while handling hot digestion flasks.
4. Place hot digestion flasks on asbestos mats while cooling their contents.
5. Exercise care in weighing, transferring, and disposing l-ammo-2-naphthoI-4-sulfomc acid as its
toxological properties have not been fully evaluated.
6. Avoid inhalation of SO2 vapors during disposal of the final color-reaction mixtures. The sink
area should be well ventilated and the tap water running during disposal of the solutions.
-------
Total Phosphate and Total Orthophosphate in Liquids
EQUIPMENT
Requirements
1. Balance, analytical, 0.0001-g readability
2. Bottles, reagent, 250-ml and 1-liter
3. Bottle, reagent, Pyrex, amber, 1-liter
4. Bottle, washing-dispensing, polyethylene, 500-ml
5. Bottle, weighing; low form; cylindrical with standard taper cap; 30mm high and 60mm in
diameter
6. Cuvettes, spectrophotometer, matched with 1-cm pathlength
7. Cylinders, graduate, Pyrex, 100-ml, with standard taper stopper; A 105-ml volume mark should
be etched on each cylinder with a glass-marking pencil.
8. Desiccator, Pyrex or small stainless-steel cabinet-type
9. Filler, pipet (e.g., Will Scientific Co. no 22105)
10. Flasks, Erlenmeyer, Kimax or Pyrex, 250-ml, with wide mouth
11. Flasks, volumetric, 100-ml and 2-liter
12. Foil, aluminum
13. Gloves, asbestos
14. Hood, capable of removing acid fumes
15. Hot plate, electric (230 volts), rectangular, 12 x 20 inches (~ 30x51 cm), with input
proportioner and 79- to 510-C temperature range (e.g., Lindberg Hevi-duty hot plate, type H-2,
Matheson Scientific Co. no. 28650-20)
16. Mats, asbestos, 12x12 inches (~ 30 x 30 cm)
17. Meter, pH (e.g., Corning Model 7, with Corning pH electrode no. 476022 with triple-purpose
glass membrane and Corning reference calomel electrode no. 476002 with asbestos junction)
18. Pencil, diamond, for marking glass
19. Pipets, serological, class A accuracy, 5-ml
20. Pipets, volumetric, Pyrex; 1-, 5-, and 10-ml
21. Spatula, stainless-steel (e.g., Scoopula®, Fisher Scientific Co. no. 14-357)
22. Spectrophotometer, operative at 650 nm, with matched cuvettes having a 1-cm pathlength (e.g.,
Beckman model B spectrophotometer)
Preparation
Soak all glassware in the special cleaning solution (See Reagents section below). Rinse well with
distilled water, and dry before using. Avoid contact of glassware with soaps or detergents as they
contain phosphates.
REAGENTS
1. Cleaning solution for glassware: Slowly add 250 ml concentrated hydrochloric acid to 750 ml
distilled water. Cool before using.
2. Stock organic phosphate solution(21.98 mgPO4/l): As needed, dissolve 0.1 g anhydrous beta
sodium glycerophosphate (e.g., C3H7Na2O6P'51/2 H2O, Fisher Scientific Co. no. 314, pre-
viously heated for 1 hour at 105 C to drive off water) in distilled water and dilute with same to
2 liters.
-------
METHODS OF SOLID WASTE TESTING
3. Stock inorganic phosphate solution no. 1 (lOOOmg PO4/1): Dissolve 1.433g KH2PO4
(previously dried for 1 hour at 105 C) in distilled water and dilute with same to 1 liter. Store in
a 1-liter reagent bottle.
4. Stock inorganic phosphate solution no. 2 (10 mgPO4/l): Prepare as needed by diluting 10 ml
stock inorganic phosphate solution no. 1 to 1 liter with distilled water.
5. Sulfunc acid solution containing bismuth: Slowly add 370ml concentrated sulfunc acid
(S.G. 1.84) to 600 ml distilled water. While the solution is warm, add 4.8 g Bi(NO3)3-5H2O.
Cool the solution to room temperature, and dilute with distilled water to 1 liter. Store in a
1-liter reagent bottle.
6. Potassium persulfate, A.C.S., anhydrous (K2 S2 O8).
7. Ammonium molybdate solution: Dissolve 48 g (NH4)6MO,O24 -4H2O in 800ml distilled
water. Add 2.5 ml concentrated NH4OH (S.G. 0.90), and dilute with distilled water to 1 liter.
8. Amino solution: In 500 ml distilled water, dissolve (in order specified) 18.5g sodium sulfite
(Na2SO3), 0.500 g l-amino-2-naphthol-4-sulfomc acid, and 31 g sodium metabisulfite (sodium
pyrosulfite, Na2 S2 Os). Store in an amber reagent bottle, wrapped in aluminum foil to exclude
light. Prepare fresh once a month.
9. Buffer solution, pH 2.0 ± 0.02 at 25 C (e.g., Fisher Scientific Co. no. SO-B-96).
10. Potassium chloride solution, saturated (e.g., Corning no. 477000).
STANDARDIZATION
The calibration of the method is initiated by developing the molybdenum blue color in eight
standard inorganic phosphate solutions that range in concentration from 0.5 to 5.0 mgPO4/l. After
measuring the absorbance of each standard solution against that of a similarly treated water blank, a
calibration graph is prepared.
The steps of the calibration procedure are as follows:
Procedure
1. Prepare a blank sample by transferring
100ml distilled water to a 100-ml glass-
stoppered cylinder.
2. Prepare eight calibration standards by indi-
vidually transferring a 2-, 5-, 10-, 15-, 20-,
25-, 30-, 40-, and 50-ml aliquot of standard
inorganic solution no. 2 to an appropriately
labelled 100-ml glass-stoppered cylinder.
Then dilute each with distilled water to
100ml.
3. Add 5 ml sulfuric acid reagent containing
bismuth to each of the nine cylinders.
Stopper and invert several times to mix the
contents.
4. Add 5 ml ammonium molybdate reagent to
each cylinder. Restopper and invert to mix
the contents.
Comments
2. The calibration standards contain 0.2, 0.5,
1.0, 1.5, 2.0, 2.5, 3.0, 4.0, and 5.0 mg
PO4/1, respectively.
3. Use a pipet filler and a clean serological
pipet to add each reagent m steps 3-5.
4. A yellowish color forms.
-------
Total Phosphate and Total Orthophosphate in Liquids
5. Without delay, add 5 ml amino solution to
each cylinder. Restopper and invert to mix
the contents. Note the time.
6. Fifteen minutes after mixing the samples in
step 5, transfer an aliquot of each solution
to a spectrophotometer cuvette having a
1-cm pathlength.
7. Measure at 650 nm the absorbance of each
standard solution against that of the water
blank, set at zero.
8. Prepare a calibration graph (i.e., on regular
graph paper plot the absorbance values as
ordinates and the phosphate concentrations
as abscissas; connect the points).
5. Molybdenum blue begins to form directly
upon the addition of this reagent to a
standard solution. The color intensity in-
creases within the first few minutes and
appears stable after 15 minutes.
6. The color remains stable for at least 25
minutes (i.e. from 15 to 40 minutes after
mixing the samples in step 5).
7. The final pH of each developed solution
should be 0.65 ± 0.05.
8. The graph should be linear.
SAMPLE PREPARATION
Since the total phosphate and total orthophosphate determinations are performed on aliquots of
the total aqueous sample, no sample preparation is required. It is advantageous, however, to minimize
the oxidation of a sample (particularly its ferrous iron content) during its collection and delivery to
the laboratory. If the collection vessel is quickly and completely filled and then tightly sealed, sample
oxidation will be minimized. In this way, the ferric iron concentration may be prevented from rising
to the level of interference. (See Method Evaluation Section of this Procedure.)
PROCEDURES
The procedures recommended here are applicable for the direct determination of the total
phosphate and total orthophosphate contents of refuse extracts, landfill leachates, and related water
samples containing up to 5 mg PO4/1. The range of applicability has routinely been extended to
100 mg PO4/1 by diluting an appropriate aliquot of the sample to 100 ml before initiating the
analysis.
Duplicate determinations of the total phosphate and total orthophosphate contents of a standard
or wastewater sample should be performed. A reagent blank should also be processed with each set of
samples. The blank for the total phosphate analysis (reagent blank no. 1) measures the color
produced by all the reagents and is therefore subjected to both the digestion and the color
development. The blank for the total orthophosphate analysis (reagent blank no. 2) measures only
the color produced by the reagents used in the color development.
Determination of Total Phosphate
Procedure
Comments
1. Prepare reagent blank no. 1 by transferring
100ml distilled water to a labelled, wide
mouth 250-ml Erlenmeyer flask.
-------
METHODS OF SOLID WASTE TESTING
2. Transfer an appropriate aliquot of a standard
solution or wastewater to a labelled wide-
mouth 250-ml Erlenmeyer flask.
3. If necessary, dilute the sample aliquot in the
flask to 100 ml with distilled water.
4. Process a second aliquot of the standard
solution or wastewater as directed in steps 2
and 3.
5. Add 5 ml sulfuric acid reagent containing
bismuth to each flask. Mix the contents of
the flask by swirling.
6. Add 0.8 g potassium persulfate to each flask.
Mix the contents of the flask by swirling.
7. Place each flask on a previously heated hot
plate.
8. Using maximum heating, boil the contents
of each flask for 40 minutes.
9. After digestion is completed, remove each
flask from the hot plate.
10. Wash down the inner surface of each flask
with a fine stream (10 ml) of distilled water.
11. Cool the contents of each flask to room
temperature (25 C ±5 C).
12. Transfer the contents of each flask to a
correspondingly labelled, 105-ml marked,
glass-stoppered cylinder.
2. a)
b)
c)
7.
An appropriate aliquot contains less than
0.5mgPO4.
A 10-ml aliquot of the stock organic
phosphate solution can be used for the
standard analysis.
A pipet filler and clean volumetric pipet
should be used to transfer each sample.
5. a)
b)
c)
b)
Wear safety glasses while handling acids
and mixtures thereof.
Use a pipet filler and clean serological
pipet to add the reagent.
A sample, containing sulfide, will turn
brown on addition of this reagent. If this
occurs, modify the procedure as suggest-
ed by ASTM. (See Method Evaluation
section of this procedure.)
6. Previously weighed glassine paper may be
used as support while weighing and trans-
ferring the potassium persulfate to each
flask.
a) Turn hot plate on to maximum heating
position 30 minutes prior to use.
The directions concerning the hot plate
apply to the apparatus specified in the
Equipment section of this procedure.
The sample volume normally decreases
to about 10 to 15ml during the
40-minute digestion. A white precipitate
forms if the volume falls below 10 ml.
If the sample volume falls below 25 ml
dunng the first 35 minutes of the diges-
tion, add distilled water to the sample to
maintain a volume between 25 and
100 ml.
Wear asbestos gloves while handling hot
flasks.
Support hot flasks on asbestos mats.
10. A dispensing-washing bottle can be used to
dispense the distilled water.
11. Cooling is usually completed after 45 to 60
minutes.
8. a)
b)
9. a)
b)
-------
Total Phosphate and Total Orthophosphate in Liquids
13. Using a fine stream (10ml) of distilled
water, rinse each flask several times. Add
each rinse to its corresponding sample, con-
tained in a cylinder.
14. Dilute the contents of each cylinder to
105 ml with distilled water. Stopper and
invert to mix the contents.
15. Add 5 ml ammonium molybdate solution to
each cylinder. Restopper and invert to mix
the contents.
16. Without delay, add 5 ml amino addition to
each cylinder. Restopper and invert to mix
the contents. Note the time.
17. Fifteen minutes after mixing the samples in
step 16, transfer an aliquot of each solution
to a spectrophotometer cuvette with a 1-cm
pathlength.
18. Measure at 650 nm the absorbance of each
standard solution or wastewater against that
of reagent blank no. 1, set at zero.
19. Obtain the Orthophosphate concentration
(mgPO4/l) of each solution from the cali-
bration graph.
20. If the sample aliquot (used in step 2) was
less than 100 ml, calculate the phosphate
concentration of the original (undiluted)
standard solution or wastewater as directed
in the Calculations section of this Procedure.
21. Report the observed total Orthophosphate
concentration as the total phosphate.
14. Mixing of insufficiently cooled samples may
result in excessive generation of heat, expan-
sion of flask contents, and expulsion of both
the stopper and acidic solution.
15. a) Use a pipet filler and clean serological
pipet to add each reagent in steps 15
and 16.
b) A yellowish color forms on addition of
this reagent.
16. Molybdenum blue begins to form upon the
addition of this reagent to the standard
solution or wastewater. The color intensity
increases within the first few minutes and
appears stable after 15 minutes.
17. The color remains stable for at least 25
minutes (i.e., from 15 to 40 minutes after
mixing the samples in step 16.)
18. The final pH of each developed solution
should be 0.65 ± 0.05.
Determination of Total Orthophosphate
Procedure
1. Prepare reagent blank no. 2 by transferring
100 ml distilled water to a labelled, 100-ml
glass-stoppered cylinder.
2. Transfer an appropriate aliquot of the stan-
dard solution of wastewater to a labelled,
100-ml glass-stoppered cylinder.
Comments
2. a) An appropriate aliquot contains less than
0.5 mgPO4.
b) A 10-ml aliquot of stock inorganic phos-
phate solution no. 2 can be used for the
standard analysis.
c) A pipet filler and clean volumetric pipet
should be used to transfer each sample.
-------
METHODS OF SOLID WASTE TESTING
3.
4.
5.
6.
7.
8.
9.
Dilute the contents of each cylinder, if
necessary, to 100 ml with distilled water.
Stopper and invert to mix the contents.
Process a second aliquot of the standard
solution or wastewater as directed in steps 2
and 3.
Add 5 ml sulfuric acid reagent containing
bismuth to each cylinder. Stopper and invert
to mix the contents.
Add 5 ml ammonium molybdate solution to
each cylinder. Restopper and invert to mix
the contents.
Without delay, add 5 ml amino solution to
each cylinder. Restopper and invert to mix
the contents. Note the time.
5. a) Wear safety glasses while handling acids
or mixtures thereof.
b) Use a pipet filler and a clean serological
pipet to add each reagent in steps 5-7.
c) A sample, containing sulfide, will turn
brown on addition of this reagent. If this
occurs, modify the procedure as suggest-
ed by the American Society for Testing
and Materials (ASTM). (See Method
Evaluation section of this Procedure).
6. A yellowish color forms when this reagent is
added.
7. Molybdenum blue begins to form upon the
addition of this reagent to the standard
solution or wastewater. The color intensity
increases within the first few minutes and
appears stable after 15 minutes.
8. The color remains stable for at least 25
minutes (i.e., from 15 to 40 minutes after
mixing the samples in step 7).
9. The final pH of each developed solution
should be 0.65 ± 0.05.
Fifteen minutes after mixing the samples in
step 7, transfer an aliquot of each solution
to a spectrophotometer cuvette with a 1-cm
pathlength.
Measure at 650 nm the absorbance of each
standard solution or wastewater against that
of reagent blank no. 2, set at zero.
1 0. Obtain the orthophosphate concentration
(mgPO4/l) of each solution from the cali-
bration graph.
If the sample aliquot (used in step 2) was
less than 1 00 ml, calculate the ortho-
phosphate concentration of the original (un-
diluted) standard solution or wastewater
sample as directed in the following section.
CALCULATIONS
Since the total phosphate concentration is reported in terms of the total orthophosphate concentra-
tion of a sample, the following formula suffices for the calculation of either the total phosphate or total
orthophosphate concentration of the original (undiluted) standard solution or wastewater sample.
11
where:
C = mg PO4/1 obtained from the calibration graph
V = ml of sample used in the test
-------
Total Phosphate and Total Orthophosphate in Liquids
METHOD EVALUATION
interferences
Studies performed in the Solid and Hazardous Waste Research Laboratory have demonstrated that
the color development of a 100-ml sample is not affected by the presence of 100 mg chloride or
50 mg calcium. Ferric iron may delay the color development for a few minutes, but the maximum
color intensity is always attained within 15 minutes in the presence of 20 mg ferric iron. The ASTM
has reported only a 2 percent error in the analyses of solutions containing silica concentrations fifty
times larger than their phosphate concentrations (2, sect. 15, p. 47). Nitrite, several mgsulfide, and
>75 mg chromate per liter, however, will interfere with the test. The analyst should use the
modifications proposed by ASTM to overcome these interferences (13).
Accuracy
Total phosphate method.
The accuracy of the total phosphate procedure was first evaluated by analyzing four aliquots of
three standard solutions of organic phosphates: beta sodium glycerophosphate, 3-adenylic acid, and
barium fructose 6-phosphate. The average percent recoveries of the theoretical phosphate
concentrations of the three solutions were 99.6, 91.3, and 86.3, respectively (See Table 1). Although
the phosphate recoveries from the 3-adenylic acid and barium fructose 6-phosphate solutions were
lower than the recovery from the beta sodium glycerophosphate solution, the observations compare
favorably with those of Gales, Julian and Kroner (4).
Four diluted leachate samples were also analyzed before and after the addition of an aliquot of
one of the organic phosphate solutions. The percent recovery of phosphate added as 3-adenylic acid
(3AA) to two landfill leachates was 92.6 whereas the percent recovery of phosphate added as barium
fructose 6-phosphate (BF6P) to the same leachates was 86.7. When aliquots of the beta sodium
glycerophosphate (BSG) solution were added to four leachates, the percent phosphate recovery
varied from 97.1 to 99.1; the average was 98.6. The excellent recovery of phosphate from two
leachates, (namely, nos. 71-303 and 73-49) was particularly significant because these samples
contained substances that prevented the determination of their total phosphate content by the
vanadomolybdophosphoric acid and stannous chloride methods (7, p. 78-93).
Total Orthophosphate method.
The accuracy of the total Orthophosphate method was first evaluated by analyzing an inorganic
phosphate standard obtained from the Analytical Quality Control Laboratory, National Environ-
mental Research Center-Cincinnati, U.S. Environmental Protection Agency. The percent recovery of
the theoretical phosphate concentration was 102. (See Table 2.)
Two diluted leachate samples were also analyzed before and after adding an aliquot of a standard
solution of monobasic potassium phosphate (KH2PO4). The percent phosphate recovery was 100 in
each case. The excellent phosphate recovery from leachate no. 73-49 was particularly significant in
view of the 290 mg iron (ferrous and ferric) present in the aliquot analyzed.
Precision
The reproducibility of the observations of the total phosphate and total Orthophosphate contents
of refuse extracts and landfill leachates was evaluated by calculating the pooled standard deviation
and coefficient of variation of groups of duplicate observations. The groupings were based on sample
type and source, and the subgroupings, on range of phosphate concentration. A review of the data,
presented in Tables 3 and 4, reveals that the coefficient of variation never exceeded 0.03.
-------
METHODS OF SOLID WASTE TESTING
ACKNOWLEDGMENTS
The author wishes to thank Dirk Brunner and the staff of the Landfill Disposal Project, Solid and
Hazardous Waste Research Laboratory, for supplying the refuse and landfill leachate samples. Special
thanks are also extended to Israel Cohen, Monitoring and Analysis Project, for preparing the refuse
extracts.
TABLE 1
ACCURACY OF THE TOTAL PHOSPHATE METHOD
Sample
Identity
mgP04/l
diluted
sample
Added
standard
mgP04/l
% Recovery
standard
Observed
Avg.
Standards
Beta sodium
glycerophosphate
(BSG)
3-Aden ylie acid
(3AA)
Barium fructose
6-phosphate
(BF6P)
2.198
2.198
2.198
1.099
.367
.367
.367
0.684
.200
.200
1.200
0.600
Boone Co., Ky., Landfill Leachates
no. 71-303 2.10
with BSG
with BSG
no. 72-125
with BSG
with 3AA
with BF6P
no. 72-126
with BSG
with 3AA
with BF6P
no. 73-49
with BSG
2.59
1.40
1.01
1.099
1.099
1.099
0.684
0.600
1.099
0.684
0.600
2.198
100.0
99.1
100.0
99.1
91.4
91.4
91.4
91.2
85.6
88.3
84.9
86.6
99.1
100.0
99.1
92.6
86.7
97.3
92.6
86.7
99.1
99.6
91.3
86.4
99.6
10
-------
Total Phosphate and Total Orthophosphate in Liquids
TABLE 2
ACCURACY OF THE TOTAL ORTHOPHOSPHATE METHOD
Sample
Identity
mgP04/l
diluted
sample
Added
standard
mgP04/l
%Recovery
standard
Standard
Analytical Quality
Control Lab.
nutrient soln.
no. 2
0.975
102
Boone Co., Ky.,
no. 73-9
with KH2 PO4
no. 73-49
with KH2 PO4
Landfill Leach ates
0.170
0.645
1.100
1.100
100
100
TABLE 3
PRECISION OF DUPLICATE TOTAL PHOSPHATE DETERMINATIONS OF
REFUSE EXTRACTS AND LEACHATES FROM THE RESEARCH LANDFILL
OPERATION IN BOONE COUNTY, KENTUCKY
Type of
sample
Refuse
extracts*
Leachates
Leach ates
Sample
source
Cell no. 1
refuse
Cell no. 1
upper
pipe
Cell no. 1
lower
pipe
No. of
Group samples
in group
Total
Subgroup A
Subgroup B
Total
Subgroup A
Subgroup B
Total
Subgroup A
Subgroup B
14
4
10
39
3
36
33
9
24
Range of total
PO4 cone, in
mg/1
>
1
1
10
1
1
10
1
1
10
<
100
10
100
100
10
100
100
10
100
Mean
mgP04/l
(M)
20.66
7.30
26.00
29.94
8.43
31.73
14.41
6.87
17.25
Pooled
standard
deviation
-------
METHODS OF SOLID WASTE TESTING
TABLE 4
PRECISION OF DUPLICATE TOTAL ORTHOPHOSPHATE DETERMINATIONS OF
LEACHATES FROM THE RESEARCH LANDFILL OPERATION IN BOONE COUNTY, KENTUCKY
Sample
source
Cell no. 1
upper
pipe
Cell no. 1
lower
pipe
Group
Total
Total
Subgroup A
Subgroup B
No. of
samples
in group
23
18
10
8
Range of total
PO4 cone, in
mg/1
>
10
1
1
10
<_
100
100
10
100
Mean
mgP04/l
(M)
31.50
11.53
6.26
18.12
Pooled
standard
deviation
-------
LABORATORY PROCEDURE FOR DETERMINING
THE TOTAL PHOSPHATE CONTENT
OF SOLID WASTES
Nancy S. Ulmer*
DISCUSSION 2
SAFETY PRECAUTIONS 2
EQUIPMENT 2
REAGENTS 3
STANDARDIZATION 4
SOLID WASTE PREPARATION 5
PROCEDURE 5
CALCULATIONS 9
METHOD EVALUATION 9
ACKNOWLEDGMENTS 10
REFERENCES 11
'Research Chemist, Criteria Development Branch, Water Supply Research Laboratory,
National Environmental Research Center - Cincinnati, Miss Ulmer was formerly with
the Solid and Hazardous Waste Research Laboratory of NERC-Cincinnati
-------
METHODS OF SOLID WASTE TESTING
DISCUSSION
The significance of phosphorus as a solid waste characteristic becomes apparent when one
considers that it is an essential nutrient. Along with nitrogen, phosphorus promotes the growth of
algae in streams. Discharging incinerator wastewater and landfill leachates containing phosphorus into
receiving streams will contribute to the deterioration of stream water quality and the eutrophication
of lakes. A knowledge of the concentration and distribution of phosphorus in solid wastes and
related water samples is, therefore, important to the engineers and scientists responsible for the
development and evaluation of solid waste and water quality management systems.
Analysts have employed a variety of methods to determine the phosphorus content of solid wastes
and related materials (1-11). The condensed phosphates and organically bound phosphorus present in
a sample must first be converted to orthophosphate by either ashing or digesting the sample. The
total orthophosphate content of the treated and diluted sample is then determined with the use of
volumetric, gravimetric, colorimetric, or atomic absorption technique.
The technique outlined here recommends the digestion of 1-g solid waste samples with sulfuric and
nitric acids. After the digestion is completed, the sample is cooled, filtered, and carefully diluted. The
orthophosphate concentration of an appropriate aliquot of solution is then determined colorimet-
rically using the amino reduction method (2, p. 46-50). The solution is therefore treated with a
sulfuric acid reagent containing bismuth. Ammonium molybdate is added to form molyb-
dophosphate. The latter, in turn, is reduced to molybdenum blue with 1-amino-2-naphthol-4-sulfonic
acid. The bismuth salt in the acid reagent provides a fourfold increase in the intensity of the blue
color.
SAFETY PRECAUTIONS
To avoid the physical and chemical hazards associated with the maintenance of the glassware and
the performance of each analysis:
1. Wear safety glasses when handling concentrated acids and mixtures thereof.
2. Perform all acid digestions in a hood to avoid inhalation of fumes.
3. Wear asbestos gloves while handling hot flasks.
4. Avoid contact of skin, clothing, metal, and painted surfaces with the molybdate reagent as it is
corrosive.
5. Exercise care in weighing, transferring, and disposing l-amino-2-naphthol-4-sulfonic acid as its
toxicological properties have not been fully evaluated.
6. Avoid inhalation of SO2 vapors when disposing of the final color-reaction mixtures. The sink
area should be well ventilated and tap water should be running during disposal of the solutions.
EQUIPMENT
Requirements
\. Apparatus, digestion, micro-Kjeldahl, with six individual heaters and controls (e.g., Fisher
Scientific Co. no. 21-131-5)
2. Balance, analytical, 0.0001 -g readability
3. Bottles, reagent, Pyrex, 250-ml and 1-liter
-------
Total Phosphate in Solids
4. Bottle, reagent, Pyrex, amber, 1-liter
5. Bottle, washing-dispensing, polyethylene, 500-ml
6. Bottle, weighing, low form, cylindrical with standard taper cap, 30 mm high and 60 mm in
diameter
7. Cuvettes, spectrophotometer, matched, with 1-cm pathlength
8. Cylinders, graduate, Pyrex, with standard taper stopper, 100-mI
9. Desiccator, Pyrex or small, stainless-steel, cabinet-type
10. Dishes, aluminum, moisture, 89- x 50-mm, with tightly fitting lids (e.g., Arthur H. Thomas Co.,
no. 3840-F30)
11. Dispenser, tilting, with 25-ml reservoir, for use with 500-ml Erlenmeyer flask (e.g., Lab. Glass,
Inc., no. LG-7915)
12. Filler, pipet (e.g., Will Scientific Co. no. 22105)
13. Flask, Erlenmeyer, 500-ml, with 20/40 ground glass neck to receive tilting dispenser
14. Flasks, Kjeldahl, micro, 100-ml (e.g., Scientific Glass Blowing Co. no. SGB-16350)
15. Flasks, volumetric, 100-ml and 1-liter
16. Foil, aluminum
17. Funnel, filtering, Pyrex, 65 mm in diameter, with 60° angle and short stem
18. Gloves, asbestos
19. Hood, capable of removing acid fumes
20. Meter, pH (e.g., Corning Model 7 with Corning pH electrode no. 476022 with triple-purpose
glass membrane and Corning reference calomel electrode no. 476002 with asbestos junction)
21. Oven, forced-draft, capable of maintaining a 70- to 75-C temperature over a 4-hour period
22. Paper, filter, Whatman no. 7, 12.5-cm diameter
23. Paper, glassine
24. Pipets, serological, Pyrex, class A accuracy, 5-ml
25. Pipets, volumetric, Pyrex, 1-, 5-, and 10-ml
26. Spatula, stainless-steel (e.g., Scoopula®, Fisher Scientific Co. no. 14-357)
27. Spectrophotometer, operative at 650 nm; with cuvettes having a 1-cm pathlength (e.g.,
Beckman model B spectrophotometer)
28. Support for funnels, 65 mm in top diameter
Preparation
Soak all glassware in the special cleaning solution (see Reagent section in this Procedure). Rinse
well with distilled water, and dry before using. Avoid contact of glassware with soaps and detergents
as they contain phosphates.
REAGENTS
1. Cleaning solution for glassware: Slowly add 250 ml concentrated hydrochloric acid to 750 ml
distilled water. Cool before using.
2. Beta sodium glycerophosphate, ACS. Heat C3 H7 Na2 O6 P.5-1/2 H2 O (e.g., Fisher Scientific Co.
no. S-314) for 1 hour at 105 C to drive off water. Store in a desiccator. The dried solid contains
43.96 percent phosphate (PO4 ) by weight.
-------
METHODS OF SOLID WASTE TESTING
3. Stock inorganic phosphate solution no. 1 (1000 mg PO4/1): Dissolve 1.433gKH2PO4
(previously dried for 1 hour at 105 C) in distilled water and dilute with same to 1 liter. Store in
a 1-liter reagent bottle.
4. Stock inorganic phosphate solution no. 2 (10 mg PO4/1): Prepare as needed by diluting 10 ml
stock inorganic phosphate solution no. 1 to 1 liter with distilled water.
5. Sulfuric acid, concentrated, ACS. (S.G. 1.84).
6. Nitric acid, concentrated, ACS.
7. Sulfuric acid reagent containing bismuth: Slowly add 370 ml concentrated sulfuric acid
(S.G. 1.84) to 600 ml distilled water. While the solution is warm, add 4.8 gBi(NO3)3-5H2O.
Then cool the solution to room temperature and dilute with distilled water to 1 liter. Store in a
1-liter reagent bottle.
8. Ammonium molybdate solution: Dissolve 48 g (NH4)6MO7O24 -4H2O in 800ml distilled
water. Add 2 5 ml concentrated NH4OH (S.G. 0.90), and dilute with distilled water to 1 liter.
9. Amino solution: In 500 ml distilled water, dissolve (in order specified) 18.5 g sodium sulfite
(NaaSO3), 0.500 g l-amino-2-naphthol-4-sulfonic acid, and 31 g sodium metabisulfite (sodium
pyrosulfite, Na2 S2 O5). Store in an amber reagent bottle that has been wrapped in aluminum
foil to exclude light. Prepare fresh once a month.
10. Buffer solution, pH 2.0 ± 0.02 at 25 C (e.g., Fisher Scientific Co. no. SO-B-96).
11. Potassium chloride solution, saturated (e.g., Corning no. 477000).
STANDARDIZATION
The calibration of the method is initiated by developing the molybdenum blue color in eight
standard inorganic phosphate solutions, ranging in concentration from 0.5 to 5.0 mg PO4/1. After
measuring'the absorbance of each standard solution against that of a similarly treated water blank, a
calibration graph is prepared.
The steps of the calibration procedure are as follows:
Procedure Comments
1. Prepare a blank sample by transferring
100ml distilled water to a 100-ml glass-
stoppered cylinder.
2. Prepare eight calibration standards by in- 2. The calibration standards contain 0.2, 0.5,
dividually transferring a 2-, 5-, 10-, 15-, 20-, 1.0, 1.5,2.0,2.5,3.0,4.0, and 5.0mgPO4/l,
25-, 30-, 40-, and 50-ml aliquot of standard respectively.
inorganic phosphate solution no. 2 to an
appropriately labelled 100-ml glass-
stoppered cylinder. Then dilute each with
distilled water to 100 ml.
3. Add 5 ml sulfuric acid reagent containing 3. Use a pipet filler and a clean serological
bismuth to each of the nine cylinders. plpet for each of the three reagents added in
Stopper and invert several times to mix the steps 3-5.
contents.
4. Add 5 ml ammonium molybdate reagent to 4 A yellowish color forms.
each cylinder. Restopper and invert to mix
the contents.
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Total Phosphate in Solids
5. Without delay, add 5 ml ammo solution to
each cylinder. Restopper, invert to mix, and
note the time.
6. Fifteen minutes after mixing the sample in
step 5, transfer an aliquot of each solution
to a spectrophotometer cuvette having a
1-cm pathlength.
7. Measure at 650 nm the absorbance of each
standard solution against that of the water
blank, set at zero.
8. Prepare a calibration graph (i.e., on regular
graph paper, plot the absorbance values as
ordinates and the phosphate concentrations
as abscissas. Connect the points.)
7.
Molybdenum blue begins to form upon the
addition of this reagent to a standard solu-
tion. The color intensity increases within the
first few minutes and appears stable after 15
minutes.
The color remains stable for at least 25
minutes (i.e., from 15 to 40 minutes after
mixing the sample in step 5).
The final pH of each developed solution
should be 0.65 ± 0.05.
8. The graph should be linear.
SOLID WASTE PREPARATION
A solid waste sample must undergo physical preparation before its characterization is initiated.
First, most of the glass and the metallic and magnetic iron particles are removed manually. Then the
waste is dried to a constant weight in a forced-air or mechanically convected oven. A temperature of
70 to 75 C is used to dry municipal refuse or compost. The particle size of the dried sample is then
reduced to 2 mm (or less) using a hammermill, pulverizer, and laboratory mill. Finally, since samples
may absorb moisture during the grinding and mixing process, they are redned for 4 hours at the
previously specified temperature and stored in a desiccator until the analyses are completed.
PROCEDURE
Duplicate determinations of the total phosphate content of a solid standard or waste sample
should be performed. Initially, two different reagent blanks should also be processed. Reagent blank
no. 1 measures the color produced by all the reagents and is therefore subjected to both the digestion
and the color development (steps 1-34). Reagent blank no. 2 measures only the color produced by
the three reagents used in the final color development (steps 28-34). If the initial analyses
demonstrate that the absorbance of reagent blank no. 1 equals that of blank no. 2, the analyst can
conclude that phosphate is not present in the sulfuric and nitric acids used to digest the samples.
Thereafter the preparation of reagent blank no. 1 can be omitted and blank no. 2 used as the
reference solution.
The steps of the analytical procedure are as follows1
Procedure
Label a 100-ml micro-Kjeldahl flask as
reagent blank no. 1, and place on a cold-
heater unit of a micro-Kjeldahl digestion
apparatus located in a well-ventilated hood.
Transfer an appropriate quantity of a solid
sample to a preweighed piece of glassine
paper and determine the sample weight to
the nearest 0.0001 g.
Comments
2.
Use 0.025 g dried beta sodium glycerophos-
phate (organic standard) or 1 g of prepared
solid waste
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METHODS OF SOLID WASTE TESTING
3. Quantitatively transfer the solid to an ap-
propriately labelled micro-Kjeldahl flask.
Place the latter on a cold-heater unit of the
micro-Kjeldahl digestion apparatus.
4. Select and process a second aliquot of the
solid sample as directed in steps 2 and 3.
5. Carefully flow 10ml concentrated sulfunc
acid down the side of each micro-Kjeldahl
flask.
6. Gently swirl each flask to wet the solid and
mix the contents.
7. Carefully add 5 ml concentrated nitric acid
to each flask.
8. Gently swirl the contents of each flask and
return the latter to a cold heater unit.
9. Turn the control knob of each heater to
position 1.
10. After the brown fumes have evolved from
each flask, turn each heater control knob to
position 3.
11. As the heat increases, swirl each flask to mix
its contents.
12. After heating 5 to 10 minutes at control
knob position 3, turn each control knob to
position 5 and digest each sample for 1-1/2
to 2 hours.
13. Turn off heater units and cool samples.
14. Examine each sample for completeness of
digestion.
15. If the sample is completely digested, proceed
to step 17.
16. If the sample is incompletely digested, care-
fully add 1 ml concentrated nitric acid, and
continue digestion until the solution clears.
Then turn off the heater and cool the
sample.
17. After the contents of each flask have cooled,
carefully flow 25 ml distilled water down
the side of each flask.
a) Wear safety glasses when handling acids
and mixtures thereof.
b) Use a pipet filler with a serological pipet
to add the acid to each flask.
Wear asbestos gloves while handling the
flasks in steps 6-8; heat will be generated as
the acids react with the sample.
Avoid inhaling the brown fumes that will
evolve from samples.
9. The directions concerning the heater control
knobs apply only to the apparatus specified
in the Equipment section of this Procedure.
10. Samples, containing organic matter will turn
dark brown.
11. Wear asbestos gloves while handling hot
flasks.
12. Do not allow the sample volume to drop
below 3 ml.
14. a) The solution of a completely digested
solid sample will appear colorless on
cooling. A white precipitate may be
present in a flask containing a digested
solid waste.
b) An incompletely digested sample will be
brown or tan in color.
16. a) Continue digestion using heater control
knob position 5.
b) This additional step is required for only
an occasional sample.
t
17. a) Use a 25-ml tilting dispenser attached to
a 500-ml Erlenmeyer to add the water.
b) Minimize the spattering of acid while
adding water to each flask.
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Total Phosphate in Solids
18. Return each flask to a heater unit and boil
its contents for 10 minutes
19. After boiling is completed, turn off each
heater. While waiting for the digested sam-
ples to cool to room temperature, proceed
to step 20.
20. Set up a filtering apparatus for each sample,
including reagent blank, no. 1, as follows:
Place a clean, 100-ml volumetric flask, con-
taining 25 ml distilled water, beneath a
supported funnel containing Whatman no. 7
filter paper recently washed with four 20-ml
portions of distilled water.
21. Quantitatively transfer the cooled contents
of each micro-Kjeldahl flask to its respective
filtering apparatus.
18. a) Use heater control knob position 5.
b) This treatment helps to drive off excess
nitric acid.
22. Rinse each micro-Kjeldahl flask several times
with 5- to 10-ml portions of distilled water.
Add the rinsings to the appropriate funnel.
23. After the material in each funnel is com-
pletely filtered, rinse the filter paper down
with a gentle stream (10ml) of distilled
water.
24. Allow the contents of each 100-ml volu-
metric flask to cool to room temperature
(25 ± 5 C).
25. Carefully dilute the contents of each volu-
metric flask to 100ml with distilled water.
Stopper tightly and invert to mix. Each
solution, thus prepared is labelled SolutionA.
26. Dilute a 10-ml aliquot of each solution A to
100 ml with distilled water. Each new solu-
tion is labelled Solution B.
27. To initiate the color development, transfer a
10-ml aliquot of each Solution B to an
appropriately labelled, 100-ml glass-stop-
pered cylinder.
28. Similarly prepare reagent blank no. 2 by
transferring 10ml distilled water to an ap-
propriately labelled 100-ml glass-stoppered
cylinder.
20. a) At least 30 minutes are required for
sample cooling.
b) Discard the filtrate from the four wash-
ings of each filter paper.
21. a) If the filter paper is wet, it will not
rupture when the acidic sample is slowly
added.
b) Filtering the sample into a volumetric
flask containing distilled water reduces
the generation of heat on further dilu-
tion in step 25.
22. A washing-dispensing bottle can be used to
dispense the rinses in steps 22 and 23.
23. Allow the rinse to filter through the paper
into the flask.
25. BEWARE1 Mixing of insufficiently cooled
samples may result in excessive generation of
heat, expansion of flask contents, and expul-
sion of both the stopper and acidic solution.
26. The specified dilution of Solution A suffices
for the analysis of 0.025-g beta sodium
glycerophosphate samples and for 1-g solid
waste samples containing up to 5 percent
total phosphate (PO4).
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METHODS OF SOLID WASTE TESTING
29. Dilute each cylinder to 100 ml with distilled
water. Each solution, thus prepared, is iden-
tified as Solution C.
30. Add 5 ml sulfuric acid reagent containing
bismuth to each of the cylinders. Stopper
each cylinder and invert several times to mix
the contents.
31. Add 5 ml ammonium molybdate reagent to
each cylinder. Restopper and mix the
contents.
32. With delay, add 5 ml amino solution to each
cylinder. Restopper and mix the contents.
Note the time.
33. Fifteen minutes after mixing the samples in
step 32, transfer an aliquot of each solution
to a spectrophotometer cuvette with a 1-cm
pathlength.
34. Measure at 650 nm the absorbance of
reagent blank no. 2 and each standard and
solid waste solution against that of reagent
blank no. 1, set at zero. Record the obser-
vations.
35. Obtain the orthophosphate concentration
(mgPO4/l) of each C solution from the
calibration graph.
36. Calculate the percent total phosphate in the
original solid standard or waste sample
according to the instructions in the Calcula-
tions section below.
30. a) Use a pipet filler and a clean serological
pipet for each of the three reagents
added in steps 30-32.
b) Although 10-ml ahquots of the B solu-
tions may theoretically contain up to
0.1 ml residual concentrated sulfuric
acid (from the digestion), an adjustment
in the added volume of the sulfuric acid
- bismuth reagent does not appear
necessary. The final pH of developed
solutions of digested samples has not
varied significantly from those of un-
digested inorganic standards.
31. A yellowish color forms
32. Molybdenum blue begins to form directly
upon the addition of this reagent to the
standard or waste solution. The color in-
tensity increases within the first few minutes
and appears stable after 15 minutes.
33. The color remains stable for at least 25
minutes (i.e., from 15 to 40 minutes after
mixing the sample in Step 32).
34. a) If the initial analyses reveal that the two
blanks have equal absorbance, reagent
blank no. 2 can henceforth be used as a
reference solution.
b) The final pH of each developed solution
should be 0.65 ± 0.05.
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Total Phosphate in Solids
CALCULATIONS
The percent total phosphate (% total PO4) of a solid standard or waste sample, analyzed as
recommended in the Procedure section, is calculated as follows:
% total PO4 =*j-
where
M = mg orthophosphate (PO4 ) observed per liter of solution C of the digested sample
and W = g of standard or solid waste digested in the test
This formula is based on the presence of 1 ml of solution A (or 1/100 of the solid sample) in
100 ml solution C. When any other volume of solution A is diluted to 100ml and the color is
developed as outlined, the formula must be modified as follows:
PCX, =
where
M = mg orthophosphate (PO4) observed per liter of the developed solution
V = ml of solution A in the 100 ml of developed solution
W = g standard or solid waste digested in the test
METHOD EVALUATION
Interferences
Studies performed in the Solid and Hazardous Waste Research Laboratory have demonstrated that
the color development of a 100-ml sample is not affected by the presence of 100 mg chloride or
50 mg calcium. Ferric iron may delay the color development for a few minutes, but the maximum
color intensity is always attained within 15 minutes in the presence of 20 mg ferric iron. The
American Society for Testing and Materials (ASTM) has reported only a 2 percent error in the
analyses of solutions containing silica concentrations fifty times larger than their phosphate
concentrations (1, p. 47). Nitrite, several mg sulfide, and 75 mg chromate per liter, however, will
interfere with the test. The analyst should use the modifications proposed by ASTM to overcome
these interferences (1, p. 47).
Accuracy
Duplicate 0.025-g samples of beta sodium glycerophosphate, 0.1-g samples of 3-adenylic acid, and
0.1-g samples of barium fructose-6-phosphate were all analyzed using the recommended procedure.
The average percent recoveries of the theoretical total phosphate of the three standards were 99.1,
94.0, and 89.8, respectively. Although the average percent recoveries from 3-adenylic acid and
barium fructose-6-phosphate were less than the average recovery from the beta sodium glycerophos-
phate, the observations compare favorably with the data reported by Gales, Julian, and Kroner (12).
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METHODS OF SOLID WASTE TESTING
The concentration of total phosphate in duplicate aliquots of a Boone County, Kentucky, refuse
sample (no. 71-142) was also determined before and after the addition of 0.025 g beta sodium
glycerophosphate. The average percent recovery of the added phosphate was 99.1. Additional studies
also revealed that the chloride, calcium, and iron concentrations in the C solutions of the 14 analyzed
Boone County refuse samples were all very low and, hence, noninterfenng.
Precision
The reproducibility of the method has been determined by calculating the standard deviation of
the duplicate determinations of 14 Boone County, Kentucky, refuse samples. The data are presented
in Table 1.
TABLE I
PRECISION OF THE DUPLICATE TOTAL PHOSPHATE
DETERMINATIONS OF BOONE COUNTY,
KENTUCKY, REFUSE SAMPLES
Sample No.
71-120
71-123
71-125
71-128
71-130
71-133
71-135
71-138
71-140
71-142
71-145
71-155
71-158
71-160
Observed mean %
total phosphate
2.22
0.51
0.44
0.34
0.50
1.02
0.24
0.26
0.18
0.20
0.44
0.44
0.58
0.20
Standard
deviation
0.09
0.02
0.01
0.04
0.04
0.02
0.02
0.01
0.02
0.01
0.00
0.01
0.03
0.00
ACKNOWLEDGMENTS
The author wishes to thank Dirk Brunner and the staff of the Landfill Disposal Project, Solid and
Hazardous Waste Research Laboratory, for providing the Boone County, Kentucky, refuse samples.
Special thanks are extended to Israel Cohen, Monitoring & Analysis Project, Solid and Hazardous
Waste Research Laboratory, for preparing these samples. The calcium and iron analyses, mentioned
in the Method Evaluation section, were kindly performed by Michael Fluharty while he was
associated with the Laboratory.
10
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Total Phosphate in Solids
REFERENCES
1. American Society for Testing and Materials. Standard method of test for phosphate in industrial
water. In: 1969 Book of ASTM standards, pt. 23. D515-68. sect. 1-39. Philadelphia 1969
p. 43-53.
2. Boltz, D. F. Phosphorus. In: Colonmetnc determination of nonmetals New York, Interscience
Publishers, Inc., 1958. p. 29-46.
3. Click, D., ed. Determination of organic phosphorus compounds by phosphate analyses. In
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p. 694-696.
7. Scott, W. W. Volumetric methods for the determination of phosphorus In- Standard methods of
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p. 697-699.
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mixtures by atomic absorption spectrophotometry. Analytical Biochem., 20:282-293, 1969.
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total phosphorus in filtered and unfiltered water. Journal American Water Works Association,
58(10): 1363-1368, Oct. 1966.
-It US GOVERNMENT PRINTING OFFICE. 1974— 757-581/5308
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