EPA-600/4-76-038
July 1976
Environmental Monitoring Series
       THE  APPLICATION  OF  EPA  METHOD  6  TO
        HIGH  SULFUR  DIOXIDE  CONCENTRATIONS
                               Environmental Monitoring and Support Laboratory
                                       Office of Research and Development
                                      U.S. Environmental Protection Agency
                                 Research Triangle Park, North Carolina 27711

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                RESEARCH REPORTING SERIES

Research reports of the Office of Research and Development, U.S. Environmental
Protection Agency,  have been  grouped into  five series. These five  broad
categories were established to facilitate further development and application of
environmental technology. Elimination of traditional grouping was consciously
planned to foster technology transfer and a maximum interface in related fields.
The five series are:

     1.    Environmental Health Effects Research
     2.    Environmental Protection Technology
     3.    Ecological Research
     4.    Environmental Monitoring
     5.    Socioeconomic Environmental Studies

This report has been assigned to the ENVIRONMENTAL MONITORING series.
This series describes research conducted to develop new or improved methods
and  instrumentation for the identification and  quantification of environmental
pollutants at the lowest conceivably significant concentrations. It  also includes
studies to determine the ambient concentrations of pollutants in the environment
and/or the variance of pollutants as a function of time or meteorological factors.
 This document is available to the public through the National Technical Informa-
 tion Service. Springfield. Virginia 22161.

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THE APPLICATION OF EPA METHOD 6 TO HIGH SULFUR DIOXIDE CONCENTRATIONS
                                 by
                Joseph E. Knoll and M. Rodney Midgett
                     Quality Assurance Branch
          Environmental Monitoring and Support Laboratory
           Research Triangle Park, North Carolina 27711
                 U.S.  ENVIRONMENTAL  PROTECTION AGENCY
                    OFFICE  OF  RESEARCH AND  DEVELOPMENT
              ENVIRONMENTAL MONITORING AND  SUPPORT  LABORATORY
               RESEARCH  TRIANGLE  PARK, NORTH  CAROLINA   27711

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                               DISCLAIMER

      This report has been reviewed by the Environmental Monitoring and
Support Laboratory, U.S. Environmental Protection Agency, and approved
for publication.  Mention of trade names or commercial products does not
constitute endorsement or recommendation for use.
                                   ii

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                                 CONTENTS
                                                               Page
List of Tables                                                  iv
Acknowledgments                                                  v
I    Introduction                                                1
II   Experimental                                                3
III  Results and Discussion                                      5
IV   Conclusions                                                12
V    References                                                 13
VI   Appendix - Method 6 — Determination of Sulfur Dioxide     14
     Emissions from Stationary Sources
                               m

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                            LIST OF TABLES
Number                                                           Page

  1   Comparison of Prepared Gas Mixtures with
         Values Obtained Using Method 6 	   6

  2   Sulfur Dioxide Collection Efficiencies at
         Various Concentrations 	   7

  3   Effect of Readdition of H202 to Method 6
         Impingers After Sample Collection 	   9

  4   Test for the Presence of Peroxysulfates in 3%
      H0  Solutions After Sulfur Dioxide Collection 	  11
                                  iv

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                           ACKNOWLEDGMENTS

     The authors wish to thank the following members of this Branch:
Mr. Berne I. Bennett for preparing sulfur dioxide/air mixtures and
Mr. Robert G. Fuerst for the iodimetric standardization of the sodium
metabisulfite solution used in this study.

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                               SECTION I
                              INTRODUCTION
      The Quality Assurance Branch (QAB), Environmental Monitoring and
Support Laboratory, Environmental Research Center,^of the Environmental
Protection Agency, Research Triangle Park, North Carolina is engaged in
a program to evaluate methods, recommended and promulgated, for the
measurement of pollutant emissions from stationary sources.  The present
investigation deals with an evaluation of EPA Method 6 -- a procedure for
the determination of sulfur dioxide emissions from stationary sources.
The study also attempts to answer certain questions regarding the
collection efficiency of the method and its usefulness at S02 concen-
trations higher than those previously employed.
      Method 6 is applicable to the measurement of S02 emissions from
                                                                      2
fossil fuel fired steam generating units.  The standard of performance
is expressed in terms of an allowable SOo emission per thermal unit
(1.4 g/10  cal when liquid fuel is burned and 2.2 g/10  cal when fossil
fuel is burned).  This standard, depending upon the proportion of excess
                                                                3
air, is equivalent to an SOp concentration in the 1000-1800 mg/m  range.
                                         4
Method 6 has been subjected to ruggedness  testing and to precision and
        5                               3
accuracy  studies over the 200-2000 mg/m  concentration range.  Results
of these investigations establish that the method is accurate below
500 mg/m3 but indicate that it acquires a S^lJLpercent negative bias
                                                         "            3
belowjthe true concentration, when S02 concentrations exceed 800 mg/m .
The present investigation is concerned with the validity of the latter
contention and with examination of features of the method that may
contribute to inaccuracy.  Further, it is desirable to have a method

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that is accurate at higher SQy concentrations, as for example,  in the
analysis of Claus Sulfur Recovery plant effluents in which S02  concen-
                         3
trations exceed 3000 mg/m .   This report therefore presents information
obtained on the response of Method 6 at S02 concentrations up to 80,000
mg/m .

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                              SECTION II
                             EXPERIMENTAL
      Method 6 analytical and sampling procedures (described in
Appendix I) were used with only minor modifications.  The essential
features of Method 6 rely upon the following sequence:  a measured
volume of gas is collected and passed through a filter to remove
particulate; through a midget bubbler containing 80% isopropyl alcohol
solution and glass wool to remove acid mist; and, finally, through two
midget impingers containing 3% ttp®?' wn^c'1 aDsor':)s S02 gas and oxidizes
it to FUSO,.  The latter solutions are combined and analyzed for sulfate
by the barium-thorin method.  Two modifications to the sampling trains
were made:  inclusion of additional sulfur dioxide-absorbing impingers
and separate analysis of the impingers.  In some instances, when quantities
of S02 were sampled that were sufficiently large to exhaust the ^02 in an
absorbing solution, additional H202 was added to determine the presence
of unreacted sulfite.  An FLOo solution containing copious quantities
of absorbed SOo was tested for the presence of peroxysulfates.  This
test was accomplished by boiling for 2 hours and comparing the solutions
with an unboiled aliquot that had been measured immediately after sample
collection.  A similar test was carried out using reagent grade potassium
peroxydisulfate (K2S2Og) in dilute perchloric acid solution.  A solution
of iodimetrically measured sodium metabisulfite (Na2S205) was subjected
to barium-thorin analysis after addition of \\J^2'
                 3
      A 5270 mg/m  sulfur dioxide/nitrogen standard gas mixture was
obtained from a commercial gas supplier; S02/air mixtures of 13,000,
                      3
63,900 and 79,900 mg/m  were prepared by QAB.  The tanks were connected
to a laboratory gas manifold by means of stainless steel tubing.  A
                                   3

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T-joint afforded symmetrical sampling ports to which the sampling
trains could be connected and duplicate samples withdrawn.  The
gases were used undiluted and the system was operated slightly above
atmospheric pressure.

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                              SECTION III
                        RESULTS AND DISCUSSION
      The S0? concentrations of several  bottled gas mixtures were analyzed
and the results are compared with the values stated by the manufacturers.
This comparison is illustrated in Table  I.  Both positive and negative
deviations occurred.  When a calibration gas was used (5,270 mg S02/m ),
the observed deviation was positive.  Negative deviations were found when
mixed gases prepared by QAB were employed.  However, the latter tanks were
not preconditioned nor analyzed by an independent means.  The expected
increase in negative bias with increasing S02 concentration based on a
              5                                                       3
previous study , which described the method as accurate below 500 mg/m ,
                                            3
but acquiring a negative bias above 800  mg/m , did not occur.  See Table I.
      Table II contains results of measurements which show the percent of
the total S02 sampled which was collected in each impinger.  The Table also
includes values of the quantity of gas sampled as well as the SOp concen-
tration.  There is no evidence for a dependency of the measured S0?  value
on the quantity of gas sampled.  Increasing the sampling flow rate from one
to three 1/min did not produce an increase in the fraction of the SO^ sample
collected in the second h^Op impinger.  The 80% isopropyl alcohol bubbler
retained only traces of S02-  Nearly all of the sample was collected in
the first HLOp impinger.  An exception occurred when large volumes of
highly concentrated gas were sampled.  In those instances, the use of
additional impingers assured adequate sample collection efficiency.

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 Table  1.   Comparison of Prepared Gas Mixtures with
           Values  Obtained Using Method 6.
Prepared Cone.
3
mg SC^/m
5,270*
13,300
63,900
79,900
Measured Cone.
mg SOp/ro
5,860
12,300
60,600
75,900
Relative
Deviation
+11.2
-7.5
-5.2
-5.0
Calibration gas mixture.

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Table 2.  Sulfur Dioxide Collection Efficiencies at Various Concentrations
Sample
1
2
3
4
5
6
7
8
9
10
11
12
Metered
Volume
liters
8.2
11.1
20.3
61.4
20.7
21.2
20.8
5.6
8.3
11.1
20.5
35.4
S0?
Cone.
mg/m^
5,740
6,050
5,800
5,810
12,300
60,050
61,150
76,500
77,400
74,700
76,000
74,800
Measured Impinger Collection as Percent of
Total Sample
IPA Bubbler
NIL
NIL
NIL
NIL
0.05
0.02
0.06
0.06
NIL
0.05
0.001
0.001
1st H202
100
100
99.4
97.3
99.4
67.9
72.3
99.3
98.9
99.1
57.5
33.1
2nd H202
NIL
NIL
0.6
2.6
0.5
31.9
27.5
0.6
1.1
0.9
42.3
33.0
3rd H202
NIL
NIL
NIL
0.04
NIL
0.17
0.18
NIL
0.01
NIL
0.2
32.2
a6as samples were collected at a flow rate of one liter/min, except as noted.
 Gas sample collected at three liter/min.
CA fourth and fifth
                         "•mPin9er analyzed 1.6 and 0.1 percent, respectively.

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      A test was carried out to determine if unreacted S02 was present,
after sample collection, in the absorbing solutions used in the Method 6
train.  Particular attention was given to the 80% isopropyl alcohol bubbler
that contained no added oxidant and in SCL absorbing solutions in which
the H202 had been depleted.  For this purpose, a quantity of H202 sufficient
to raise the concentration by an additional 3% was added to aliquots of
the absorbing solutions.  The solutions were then analyzed for sulfate.
Results were compared with measurements of identical aliquots that had
received no additional quantity of H202.  Table  III shows the results of
this  comparison.  Method 6 impingers contain approximately 14 millimoles
of H202 which reacts with SCL on a mole-for-mole basis.  Table III shows
that  the first  impinger had  its peroxide  depleted, the second was partially
depleted;  relatively little  of the peroxide in the third impinger was con-
sumed.  After readdition of  peroxide, the quantity of sulfate detected in
the first  H202  impinger increased, but by less than 1%.  Values corresponding
to the other absorbing solutions actually decreased.  However, those changes
were  also  small  and probably represent measurement variations.  Thus, the
results in Table III indicate that no unreacted  S02 was detected by the
experiment under consideration.
                                   8

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Table 3.  Effect of Readdition of hLOg to Method 6 Impingers  after
          Sample Collection
S02 Collected Per Impinger3
mi Hi moles
Impinger
I PA Bubbler
1st H202
2nd H^
3rd H202
With Addition
0.0123
14.42
5.37
0.0282
Without Addition
0.0124
14.37
5.46
0.0288
aAfter collecting 20.82 std.  liters of gas containing  60,600  mg  S0?/m  .

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      A test was also made to determine if peroxysulfates were produced
during sample collection.  Previous stoichiometric measurements have
shown that the primary oxidation product in the SCL/^Op reaction is
                                                                       o
sulfate and that infinitesimal amounts of other substances were formed.
However, peroxy-compounds have been postulated  to be intermediates in
the reaction between bisulfite ion and H^CL.  Since these compounds are
insensitive to barium-thorin analysis, the conversion of S02 to these
species would result in  erroneously low measurements.  Above 90°C,
aqueous solutions of peroxysulfates are rapidly decomposed to sulfates.
Therefore, the following test was made to determine if peroxysulfates
were  formed under the conditions of the present study.  Sulfur dioxide
was collected in a  3% FLOp solution.  An aliquot of the freshly prepared
solution was analyzed by the barium-thorin method; another aliquot was
measured after boiling for three hours.  A comparison was made with a
quantity of KgSpOg  in dilute HC10. solution that had received similar
treatment.  The  result,  listed  in Table IV, was only a negligible change
in the  sulfate concentration after boiling.   It must therefore be con-
cluded  that no significant quantity of peroxysulfates had been present.
      A further  test for the efficiency of conversion of sulfur(IV) to
sulfur(VI)  by 3% H202 solution was carried out as  follows:  A solution of
Na2S205 was made 3% in H202 and 0.015N in HCIO^ and analyzed by the
barium-thorin method.  The results were compared with an iodimetric
analysis.   The  iodimetric and barium-thorin analyses yielded 441 and
454 micrograms of S02/ml, respectively.
                                  10

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Table 4.  Test for the Presence of Peroxysulfates in 3% HLCU Solution
          after Sulfur Dioxide Collection
                                                 SO^ Detected

       	Solution	Millimoles

        S02 in 3% H202, freshly prepared             3.964

        S02 in 3% H202, after boiling                3.993

        K2S2°8 in 3% H2°2' freshly Prepared

        K2S2Og in 3% H202, after boiling             0.214
                                                                     o
aAfter collecting 20.82 std. liters of gas containing 12,300 mg S02/m
 in air.

 In 15 ml of solution.

C25 ml of 3% H202 solution, containing 0.004619 M K^Og and 0.012 M HC104.
                                  11

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                            SECTION IV
                            CONCLUSIONS
      A previous report  indicating that Method 6 suffers from a negative
bias below the true value when measuring S02 concentrations greater than
         3
2000 mg/m  was not confirmed by the present study.  Measurements made
using a calibration gas and other prepared gas mixtures in the 5000
to 80,000 mg S02/m  concentration range did not produce consistently low
results.  Analysis of individual impingers in multiple impinger trains
showed that more than 99% of the S02 under analysis was collected in the
first two impingers, except when sufficient sample was collected to
deplete the hLOp in the absorbing solutions, or when excessively high
flow rates were used.  Tests also showed the absence of S02 retention in
the isopropyl alcohol bubbler, absence of unreacted S02 in the peroxide
absorbing solutions and absence of peroxysulfates.  Further, analysis
of a standardized  bisulfite solution yielded results consistent with an
                                                                        5
iodimetric analysis.  From the above considerations and earlier studies,
it must be concluded that Method 6 is efficient for the measurement of
                                     3
gaseous S02  in  the 200 to 80,000 mg/m  concentration range, provided that
a sample  flow rate of about 1 liter/min is maintained and a maximum volume
of about  20  liters of gas is sampled at the higher concentration.
                                 12

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                                SECTION  V

                               REFERENCES

 1.   "Standards of Performance for Mew Stationary Sources," Federal
     Register. Vol.  36_, No. 247, December 23, 1971, pages 24890-24892.

 2.   "Standards of Performance for New Stationary Sources," Federal
     Register, Vol.  36_, No. 247, December 23, 1971, page 24879.

 3.   de Lorenzo, 0.   Combustion Engineering.   Riverside Press,  Cambridge,
     Mass., 1948.

 4.   Hamil, Henry F., "Laboratory and Field Evaluations of EPh  Methods  II,
     VI and VII," EPA-650/4-74-039, pages 31-40.

  ,-   Hamil, Henry F.  and David E. Camann.   "Collaborative Study of Method  ,-—
     for the Determination of Sulfur Dioxide Emissions from Stationary
     Sources."  EPA-650/4-74-024, pages  10-26.

 6.   Berlie, E.M., R. K. Kerr, and R. P. Rankine.  "The Role of the  Claus
     Sulfur Recovery Process in Minimizing Air Pollution," presented at the
     67th Annual Meeting of the Air Pollution Control  Association, Denver,
     Colorado, June 6-13, 1974.

 7.   Fritz, James S.  and Stanley S. Yamamura, "Rapid Microtitration  of
     Sulfate," Analytical Chemistry. 27: 1461, 1955.

 8.   Mader, P. M., "Kinetics of the Hydrogen Peroxide Sulfite Reaction  in
     Alkaline Solution," Journal of the  American  Chemical Society, 80:  2634,
     1958.

 9.   Hoffman, M. R.  and J. 0. Edwards, "Kinetics  of Oxidation of Sulfite
     by Hydrogen Peroxide in Acidic Solution," Journal of Physical Chemistry,
     79: 2096, 1975.

10.   Kolthoff, I.  M.  and I. K. Miller, "The Chemistry of Persulfate. I. The
     Kinetics and Mechanism of the Decomposition  of the Persulfate Ion  in
     Aqueous Medium," Journal of the American Chemical Society, 73:  3055,
     1951.
                                  13

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                APPENDIX





METHOD 6 — DETERMINATION OF SULFUR DIOXIDE



     EMISSIONS FROM STATIONARY SOURCES
                   14

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 21S90
       RULES AND  REGULATIONS
                               PLANT.

                               DATE_
                               RUN NO.
CONTAINER
NUMBER
1
2
TOTAL
WEIGHT OF PARTICULATE COLLECTED.
mg
FINAL WEIGHT

:XL
TARE WEIGHT

IX
WEIGHT GAIN



•
FINAL
INITIAL
LIQUID COLLECTED
TOTAL VOLUME COLLECTED
VOLUME OF LIQUID
WATER COLLECTED
IMPINGER
VOLUME.
ml




SILICA GEL
WEIGHT.
9



fl*| ml
  CONVERT WEIGHT OF WATER TO VOLUME BY DIVIDING TOTAL WEIGHT
  INCREASE BY DENSITY OF WATER.  {1 g. ml):
                                                      = VOLUME WATER, ml
                       Figure5-3.  Analytical data.

  6.6.2  Concentration in Ib./cu. ft.
                                       '--'— = 2.1>05X10-';?—
Vlioro:
          pis. Ib./f ••.{., tin \-:-.*i*.
        Mir II).
                              in-.iil.-r in .<: :
                              equation 5-5

    Mn -Total aiiiouut of paniculate matter collected,
          inf.
  V™tl-|--Volume of p:is sample through dry pas rnclT
          f--|:inn.=U> of water, 1 p. ml.
          B = Id.-al pas eon.-U.jit, 21.>3 Inches Hg-cn. ft. 11).
               m,.l.. JH.
        MojO-Mul'VuJar wotrlit of water, IS Ib./lb.-mola,
          V«e« Volume of c:is ••.!::[>> ttsroiicn the dry gas meler
               (mrt'T Cottihf I.H15 . CU. ft.
          T«a"Ab^)hito avi-r.u:i» dry gas metor temperature

         Pb«. = B:irorm-tric prc.. Indies ITf.
          Aa = CroN«-s.ictioiial area  of nozzle. «q. ft.

        6.8   Acceptable  results.  The   following
      range sets the limit on acceptable Isokinetic
      sampling results:

      If 90^< I < llOTe, the results are acceptable.
        otherwise,  reject  the results  and repeal,
        the test.

        7. Reference.
        Addendum to Specifications for Incinerator
      Testing at Federal Facilities,  PHS, NCAPC.
      Dec. 6.1967.
        Martin, Robert M., Construction Details of
      Isokinetic Source  Sampling Equipment, En-
      vironmental Protection Agency, AFTD-0531.
        Rom, Jerome J., Maintenance, Calibration.
      and Operation of Isokinetic  Source Sam-
      pling Equipment.  Environmental  Protection
      Agency, APTD-0576.
        Smith, W.  S., R. T. Shigehara,  and W.  F.
      Todd, A Method of Interpreting Stack Sam-
      pling Data, Paper presented  at the 63d  An-
      nual Meeting of  the Air Pollution Control
      Association, St. Louis, Mo., June 14-19, 1970.
        Smith. W.  S.,  et al..  Stack Gas  Sampling
      Improved and Simplified with New Equip-
      ment. APCA  paper No.  67-119, 1967.
        Specifications  for  Incinerator  Testing  at
      Federal Facilities, PHS,  NCAPC,  1967.

      METHOD 8	DETERMINATION OF STJLFTTB DIOXIDE
          EMISSIONS FROM STATIONARY SOURCES

        1. Principle and applicability.
        1.1  Principle. A gas sample is  extracted
      from the  sampling point In the stack.  The
      acid mist, including sulfur trioxide. is sepa-
      rated  from the  sulfur  dioxide. The  sulfur
      dioxide fraction is measured by the bnnum-
      thorin tltratlon method.
        1.2  Applicability. This method is appli-
      cable for the determination of sulfur dioxiae
      emissions from stationary sources  only when
      specified by tho test procedures for determin-
      ing compliance with New Source Performance
      Standards.
        2. Apparatus.
        2.1  Sampling.  See Figure 6-1.
        2.1.1   Probe—Pyres1  gloss, approximately
      6  to 6 mm.  ID,  with a heating  system  to
      prevent condensation and a filtering medium
      to remove particulate matter including  sul-
      f uric acid mist.
        2.1.2  Midget  bubbler—One, with  glass
      wool packed  In top to prevent sulfuric  acid
      mist carryover.
        2.1.3  Glass wool.
        2.1.4  Midget impingers—Three.
        2.1.5  Drying tube—Packed  with 6 to  16
      mesh Indicating-type silica gel, or equivalent.
      to dry the sample.
        2.1.6  Valve—Needle valve, or  equivalent,
      to adjust flow rate.
        2.1.7  Pump—Leak-free, vacuum type.
        2.1.8  Rate meter—Rotamptt-r or  equiva-
      lent, to me.-usure a 0-10 sc.f.h. flow range.
        2.1.9  Dry pus meter—SuiiU-iemly accurate
      to measure the s.ur.ple volume Within  !•'.
        2.1.10  Pilot tube—Type S. or equivalent.

5-0     'Trade names.
                                 FEDrRAL SCCISTER,  VOL 36. NO.  547—THURSDAY, DECEMBER  23.  1971

                                                                    15

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necesRary only If a sample traverse la re-
quired, or 11 stuck gas velocity varies  with
time.
  2.2  Sample recovery.
                  9,3.1  Glass wash bottles—Two.
                  2.2.2  Polyethylene  storage   bottles—To
                store Imptnger samples.
                  2.3  Analysis.
 PROBE (END PACKED
 WITH QUARTZ OR
 PVREXWOOL
   WE S PITOT TUBE
                                   SILICA GEL DRVING TUBE

       MIDGET BUBBLER MIDGET IMPINGERS

GLASS WOOL

           \  0/0
                            THERMOMETER
                                                                      fUMP
                                DRY GAS METER   HOTAMETER
                              Figure 6-1. S02 sampling train.
velocity.  Take  readings  at  least every five
minutes  and  when significant changes  In
stack conditions necessitate additional ad-
justments In flow rate. To  begin sampling,
position  the tip of the probo at  the first
sampling point  and start the pump. Sam-
ple proportionally  throughout the run.  At
the  concUmion  of  each run,  turn oil the
pump and record the final readings. Remove
the probe from  the stack and disconnect It
from the train. Drain the lea bath and purge
the remaining part of the train  by drawing
clean ambient air through the system for 15
minutes.
  4.2 Smiiplc recovery. Disconnect the 1m-
plngerti  alter purging. Discard the contents
of the midget bubbler. Four the contents of
the  midget implngcrs into a polyethylene
shipment lioUle. Rinse the three midget Im-
plngcrs  and the connecting tubes with dis-
tilled water and add these  washings  to the
same storage container.
  4.U Sample analysis. Transfer the contents
of the storage container to a 50 ml. volu-
metric flask. Dilute to the mark  with de-
Ionised,  distilled  water. Pipette  a  10 ml.
aliquot of this solution Into a  125 ml. Erlcn-
meyer flask. Add 40 ml. of  Isupropanul and
two to four drops of Uiorln Indicator. Titrate
to a pink endpolnt using 0.01  N barium
pcrchlorate. Bun a blank  with each  series
of samples.
  5.  Calibration.
  5.1 Use standard methods and equipment
   9.3.1  Pipettes—Transfer type,  B  ml, and
 10 ml, atees (0.1  mi,  divisions)  and 25 ml.
 elzo (0.2 ml. divisions).
   3.3.2  Volumetric flasks—SO ml.,  100 ml.,
 and 1,000 ml.
   2 3.3  Burettes—5 ml. and 50 ml.
   2.3.4  Erlcnmeyer flask—125 ml.
   3. Reagents.
   3.1  Sampling.
   3.1.1  Water—Deionlzed, distilled.
   3.1.2  Isopropanol, 80 %—Mix 80 ml, of Iso-
 prnpanol with 20 ml. of distilled water.
   3.1.3  Hydrogen peroxide,  3%—dilute 100
 ml. of 30'.'. hydrogen peroxide to 1 liter with
 distilled water. Prepare fresh dally.
   3.2  Sample recovery.
   3.2 i  Water—Dclonlzed, distilled.
   3.22  Isoprupunol, BO'.i.
   33  Annhbls.
   33.1  WatiT—Delonlzed, distilled.
   33.2  I.Miprcpanol.
   3.3.3  Thorln Indicator— l-(o-arsonophen-
 yla<:rj|-2-nuphthol-3.6-dlsulfonlc  acid,  dlso-
 dlum  s-iit (or equivalent;. Dissolve 0.20 g. In
 100 ml.  dl.sined water.
   3 3.4  Burl mil pcrchlorate  (0.01 N)—Dls-
 1'iK-e    1.95  *.   of   burlum  perchlorate
 IBfuC.'O.j, • 311 O| in  200 ml. distilled  water

       No.2i7-ri.il	3
which have been approved  by the Admlnli-
trator to calibrate tlio rotamcter. pilot tube,
dry gas meter, and probe healer,
  5.2  Standardize  the  barium  perchlorftt*
ngalnst 25 ml. of standard sulfurlc acid con-
taining 100 ml. of Isopropanol.
  0.  Calculations.
  0.1  Dry gas volume.  Correct  the sample
volume measured by  the dry gas meter to
standard conditions (70* P. and 20.02 Inches
Hg)  by using equation 6-1.
           i n .* 1 1 K
                                                                                                                         /V»PI,.A
                                                                                                                         V.  '!',„  /   t
                                                                                                                                                                  tiuut ion  0 - 1
                                                                                                        where:
                                                                                                          Vm.,4 — Volume of gus sample through the
                                                                                                                   dry gus meter  (standard  condi-
                                                                                                                   tions). cu. ft.
                                                                                                            Vlu— Volume of gas sample through the
                                                                                                                   dry  gas  meter  (meter  condi-
                                                                                                                   tions), cu. ft.
                                                                                                           T.,4— Absolute temperature at  standard
                                                                                                                   conditions, 530* R.
                                                                                                            T  — Average dry gas meter temperature.
                                                                                                                   °R.
                                                                                                           PMt— Barometric pressure at  the  orlnce
                                                                                                                   meter, Inches Hg.
                                                                                                           P,,4= Absolute pressure at standard  con-
                                                                                                                   ditions. 20.02 Inches Hg.
                                                                                                          0.2  Sulfur dioxide concentration.
                and dilute to 1 liter with Isopropanol. Stand-
                ardize with sulfurlc  acid. Barium chloride
                may be used.
                  3.3.5  Sulfurlc  acid standard  (0.01  »)~
                Purchase  or  standardize  to  ±0.0002  N
                against 0.01N NnOH  which baa previously
                been  standardized against potassium  acid
                phthalale (primary standard grade).
                  4, Procedure.
                  4.1   Sampling.
                  4.1.1  Preparation of collection train. Pour
                15  ml. of 80% Isopropanol Into  the midget
                bubbler and 15 ml. of 3% hydrogen peroxide
                into each of the first two midget impingers.
                Leave the final -midget Implngcr dry. Assem-
                ble the train  ns shown In Figure 6-1. Leak
                check  the sampling  truin at the sampling
                site by plugging the probe Inlet and pulling
                a 10 Inches Kg vacuum. A leakage rate not
                In excess  of 1% of the sampling rate Is ac-
                ceptable.  Carefully release the probe inlet
                plug and  turn oit the pump. Place  crushed
                ice around the Implngcrs. Add more ice dur-
                ing the run to keep tlic temperature of the
                gases leaving the loot Implngcr at 70° P.  or
                less.
                  4.1.2  Sample collection. Adjust the E.im-
                ple How  rate  proportional to the stack gus
where:
      Can.,—Concentration of sulfur dioxide
              at standard conditions,  dry
              basis, Ib./cu. ft.
 7.05X10-'—Conversion factor, Including the
              number  of  grams  per gram
              equivalent of sulfur dioxide
              (32 g./g.-eq.). 453.6 g./lb., and
              1,000 ml./l.. lb.-l./g.-ml.
        V, —Volume of  barium perchlorate
              tltrant used for  the sample,
              ml.
       Vlk» Volume of  barium perchlorate
              tltrant used for the blank, ml.
         .!¥•= Normality of barium perchlorate
              tltrant, g.-eq./l.
      V.ou—Total solution volume of sulfur
              dioxide, GO ml.
        V,—Volume of  sample aliquot ti-
              trated, ml.
     Vm.,j=-Volume of gas sample through
              the dry gas meter  (standard
              conditions), cu. ft., see Equa-
              tion 6-1.
                                                                         equation 6-2
  7. References.
  Atmospheric Emissions from Sulfurlc Acid
Manufacturing Processes, U.S. DIfEW,  PHS,
Division of Air Pollution, Public Health Serv-
ice Publication No. 999-AP-13,  Cincinnati,
Ohio, 1005.
  Corbett, P.  P., The Determination of BO,
and SO, In Flue Oases, Journal of the lustl-
tuto of Fuel, 24:237-243,  1801.
  Matty. R. E. and E. K.  Dlehl, Measuring
Flue-Gas SO3  and SO3, Power 101:94-87, No-
vember, 1357.
  Patton,  W.  F.  and J.  A. Brink, Jr.,  New
Equipment  and  Technique for Sampling
Chemical Process Gases, J. Air Pollution  Con-
trol Association, 13, 1C2 (19G3).

METHOD 7—DETERMINATION OF NITROGEN OXIDE
    EMISSIONS'  FROM STATIONARY SOURCES

  1. Principle  and applicability.
  1.1   Principle.  A grab  sample Is collected
in  an  evacuated llask containing a dilute
sulfurlo  acid-hydrogen   peroxide  absorbing
solution,  and   the nitrogen  oxides,  except
                                             c
                                             r~
                                             m
                                             v*

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                                                                                         5
                                                       FEDCrtAL REGISTER, VOL. 36, NO. 247—THURSDAY,  DECEMBER 23, 1971

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TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing)
1. RtPORT NO.
2.
4. TITLE AND SUBTITLE
THE APPLICATION OF EPA METHOD 6 TO HIGH SULFUR DIOXIDE
CONCENTRATIONS
7. AUTHOR(S)
Joseph E. Knoll and M. Rodney Midqett
9. PERFORMING ORGANIZATION NAME AND ADDRESS
Office of Research and Development
Environmental Monitoring and Support Laboratory
U.S. Environmental Protection Agency
Research Trianqle Park, North Carolina 27711
12/SPONSORING AGENCY NAME AND ADDRESS
Environmental Monitoring and Support Laboratory
Office of Research and Development
U.S. Environmental Protection Agency
Research Trianqle Park, North Carolina 27711
15. SUPPLEMENTARY NOTES
3. RECIPIENT'S ACCESSION-NO.
5. REPORT DATE
6. PERFORMING ORGANIZATION CODE
8. PERFORMING ORGANIZATION REPORT NO.
10. PROGRAM ELEMENT NO.
1HD621
11. CONTRACT/GRANT NO.
13. TYPE OF REPORT AND PERIOD COVERED
Fi nsl
14. SPONSORING AGENCY CODE
EPA-ORD

16. ABSTRACT
The application of EPA test method (M-6) to the analysis of higher
sulfur dioxide concentrations than had previously been employed has been
studied. The use of prepared gas mixtures showed that the method is
efficient for the measurement of gaseous sulfur dioxide in concentrations
of up to 80,000 mg/m . The investigation also showed no evidence of
retention of significant quantities of sulfur dioxide in the isopropyl
alcohol bubbler or of the production of sulfur compounds that are in-
sensitive to barium-thorin analysis. When multiple impinger trains were
employed, analysis of individual impinger contents showed that more than
99% of the sampled sulfur dioxide was collected in the first two impingers,
even at the higher concentration, except when sufficient sample was
collected to deplete the hydrogen peroxide in the absorbing solutions or
when excessively high flow rates were used. These results contradict
earlier reports that Method 6 suffers from a negative bias at high sulfur
dioxide concentrations.
17.
a. DESCRIPTORS
Sampling
Sulfur dioxide
Air pollution
Stack gases
18. DISTRIBUTION STATEMENT
RELEASE TO PUBLIC
KEY WORDS AND DOCUMENT ANALYSIS
b. IDENTIFIERS/OPEN ENDED TERMS C. COS ATI Field/Group

13B
19. SECURITY CLASS (This Report) 21. NO. OF PAGES
Unclassified 22
20. SECURITY CLASS (This page) 22. PRICE
llnrlassif ipH
EPA Form 2220-1 (9-73)
                                                          17

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