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AIR POLLUTION ASPECTS
OF
HYDROCHLORIC ACID
Prepared for the
National Air Pollution Control Administration
Consumer Protection & Environmental Health Service
Department of Health, Education, and Welfare
(Contract No. PH-22-68-25)
Compiled by Quade R. Stahl, Ph.D,
Litton Systems, Inc.
Environmental Systems Division
7300 Pearl Street
Bethesda, Maryland 20014
September 1969
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FOREWORD
As the concern for air quality grows, so does the con-
cern over the less ubiquitous but potentially harmful contami-
nants that are in our atmosphere. Thirty such pollutants have
been identified, and available information has been summarized
in a series of reports describing their sources, distribution,
effects, and control technology for their abatement.
A total of 27 reports have been prepared covering the
30 pollutants. These reports were developed under contract
for the National Air Pollution Control Administration (NAPCA) by
Litton Systems, Inc. The complete listing is as follows:
Aeroallergens (pollens) Ethylene
Aldehydes (includes acrolein Hydrochloric Acid
and formaldehyde) Hydrogen Sulfide
Ammonia Iron and Its Compounds
Arsenic and Its Compounds Manganese and Its Compounds
Asbestos Mercury and Its Compounds
Barium and Its Compounds Nickel and Its Compounds
Beryllium and Its Compounds Odorous Compounds
Biological Aerosols Organic Carcinogens
(microorganisms) Pesticides
Boron and Its Compounds Phosphorus and Its Compounds
Cadmium and Its Compounds Radioactive Substances
Chlorine Gas Selenium and Its Compounds
Chromium and Its Compounds Vanadium and Its Compounds
(includes chromic acid) Zinc and Its Compounds
These reports represent current state-of-the-art
literature reviews supplemented by discussions with selected
knowledgeable individuals both within and outside the Federal
Government. They do not however presume to be a synthesis of
available information but rather a summary without an attempt
to interpret or reconcile conflicting data. The reports are
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necessarily limited in their discussion of health effects for
some pollutants to descriptions of occupational health expo-
sures and animal laboratory studies since only a few epidemic-
logic studies were available.
Initially these reports were generally intended as
internal documents within NAPCA to provide a basis for sound
decision-making on program guidance for future research
activities and to allow ranking of future activities relating
to the development of criteria and control technology docu-
ments. However, it is apparent that these reports may also
be of significant value to many others in air pollution control,
such as State or local air pollution control officials, as a
library of information on which to base informed decisions on
pollutants to be controlled in their geographic areas. Addi-
tionally, these reports may stimulate scientific investigators
to pursue research in needed areas. They also provide for the
interested citizen readily available information about a given
pollutant. Therefore, they are being given wide distribution
with the assumption that they will be used with full knowledge
of their value and limitations.
This series of reports was compiled and prepared by the
Litton personnel listed below:
Ralph J. Sullivan
Quade R. Stahl, Ph.D.
Norman L. Durocher
Yanis C. Athanassiadis
Sydney Miner
Harold Finkelstein, Ph.D.
Douglas A. Olsen, Ph0D.
James L. Haynes
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The NAPCA project officer for the contract was Ronald C.
Campbell, assisted by Dr. Emanuel Landau and Gerald Chapman.
Appreciation is expressed to the many individuals both
outside and within NAPCA who provided information and reviewed
draft copies of these reports. Appreciation is also expressed
to the NAPCA Office of Technical Information and Publications
for their support in providing a significant portion of the
technical literature.
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ABSTRACT
Hydrochloric acid irritates the membranes of the eye
and upper respiratory tract, and prolonged exposure to low
concentrations can cause erosion of the teeth. Severe expo-
sures can result in pulmonary edema and laryngeal spasm, both
of which can be fatal. There are no known chronic or acute
systemic effects of hydrochloric acid. Hydrochloric acid is
also a phytotoxicant, and its emissions have been responsible
for plant damage in several instances. Recent data indicate
that it is a stronger phytotoxicant than reported in the
earlier literature.
The acid is strongly corrosive to most metals. Hydro-
gen chloride gas emissions are read.ily converted to hydrochlo-
ric acid by the moisture in the air. Hydrogen chloride is a
by-product of many organic chlorinating reactions; in some
instances the hydrogen chloride is collected for use, but in
small operations it may not be economically feasible to recover
the gas. Hydrogen chloride emissions result from the burning
of coal, chlorinated plastics, and paper. No information has
been found on the concentration of hydrochloric acid in the
atmosphere. The major uses of hydrogen chloride or hydrochlo-
ric acid are in manufacturing chemicals, producing metals, and
acidizing oil wells. Effective control of emissions can be
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accomplished by the use of water scrubbing equipment.
No information has been found on costs for obtaining
and maintaining the control equipment and economic losses due
to hydrochloric acid emissions. Methods of analysis for hydro-
chloric acid are based on determining the acidity or the chlo-
ride content of samples, and therefore, other strong acids or
chloride salts may cause interference.
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CONTENTS
FOREWORD
ABSTRACT
1. INTRODUCTION 1
2. EFFECTS 3
2.1 Effects on Humans 3
2.1.1 Toxic ity 3
2.1.2 Sensory Thresholds 5
2.1.3 Synergistic Effects 5
2.2 Effects on Animals 5
2.2.1 Commercial and Domestic Animals .... 6
2.2.2 Animal Experiments 6
2.3 Effects on Plants 7
2.3.1 Phytotoxicity 7
2.3.2 Incidents of Plant Damage 10
2.4 Effects on Materials 11
2.5 Environmental Air Standards 12
3. SOURCES 14
3.1 Natural Occurrence 15
3.2 Production Sources 15
3.2.1 By-Product Process 16
3.2.2 Salt-Acid Process 18
3.2.3 Chlorine-Hydrogen Synthesis 20
3.3 Product Sources 21
3.3.1 Manufacture of Chemicals 21
3.3.2 Metal Production 22
3.3.3 Other Uses 23
3.4 Other Sources . 23
3.4.1 Coal 24
3.4.2 Fuel Oil 26
3.4.3 Automobile Exhaust 26
3.4.4 Burning of Chloride-Containing
Plastics 27
3.4.5 Burning of Paper Products 28
3.4.6 DDT Production 29
3.4.7 Lemon Pulp Extraction 29
3.5 Environmental Air Concentrations 30
4. ABATEMENT 31
5. ECONOMICS 34
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CONTENTS (Continued)
6. METHODS OF ANALYSIS 35
6.1 Sampling Methods 35
6.2 Qualitative Methods 35
6.3 Quantitative Methods 36
7. SUMMARY AND CONCLUSIONS 39
REFERENCES 43
APPENDIX 52
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LIST OF TABLES
1. "Ethyl" Antiknock Compound-Tel Motor 33 Mix .... 27
2. Properties of Hydrogen Chloride and Hydrochloric
Acid 52
3. Summary of Reported Effects of Inhalation of Hydrogen
Chloride by Humans 54
4. Summary of Reported Effects of Inhalation of Hydrogen
Chloride in Animals 56
5. Summary of Reported Toxic Effects of Hydrogen
Chloride Exposure on Plants 60
6. Emissions of Hydrochloric Acid in Selected Areas of
Niagara County, New York 64
7. Hydrochloric Acid Production in the United States/
1958-1967 65
8. Production of Hydrochloric Acid by Process and
State 66
9. Major Producers of Hydrochloric Acid (Muriatic Acid)
in the United States 67
10. Consumption of Hydrochloric Acid by Uses, 1963 ... 69
11. Consumption of Hydrochloric Acid by Selected
Industries, 1963 and 1958 70
12. Chlorine Content of Selected United States Coals . . 71
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1. INTRODUCTION
Hydrogen chloride (HC1) is a hygroscopic, colorless gas
with a strong, pungent, and irritating odor. Because of its
high solubility in water, the gas fumes in moist air. An aque-
ous solution of hydrogen chloride is called hydrochloric acid.
Emissions of hydrogen chloride are readily converted to hydro-
chloric acid fumes and droplets in air or when inhaled into
the lungs. The strong dehydrating properties of hydrogen chlo-
ride can result in serious burns of the skin or mucous mem-
branes. Hydrochloric acid is extremely corrosive to most
materials. (See Table 2 in the Appendix for the properties
of hydrogen chloride and hydrochloric acid.)
Inhalation of hydrochloric acid causes coughing and
choking, as well as inflammation and ulceration of the upper
respiratory tract. Irritation of the eye membranes is another
effect, and exposure to high concentrations can cause clouding
of the cornea. The teeth can also be affected, and erosion
may result. Hydrogen chloride and hydrochloric acid are also
phytotoxicants that damage the leaves of a great variety of
plants. Several episodes of plant damage from hydrochloric
acid emissions have been reported.
The possible sources of emissions of hydrogen chloride
or hydrochloric acid are not only their commercial production
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and use, but also the burning of paper products and fossil
fuels. Many industries also produce hydrochloric acid as an
unwanted by-product in the manufacture of chemicals. The
emissions can be effectively controlled with the available
methods, which usually involve the use of water scrubbing
equipment.
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2. EFFECTS
2.1 Effects on Humans
Little information is available on the toxicity of
hydrogen chloride or hydrochloric acid when inhaled by humans.
Most of the information cited in the literature was obtained
from studies conducted 30 to 80 years ago pertaining to occu-
pational exposure.
2.1.1 Toxicity
Hydrochloric acid primarily irritates and attacks the
membranes of the eyes and upper respiratory tract. 34,73 i>ne
effects increase in severity from irritation to pulmonary
edema, and even to death in extreme cases, depending upon the
concentration and duration of exposure. No organic damage
results from exposure to 7,000 |-ig/m3 (5 ppm*).113 Irritation
of mucous membranes occurs at 15,000 ug/m3 (10 ppm),113 although
workers accustomed to hydrochloric acid exposure can work undis-
turbed, at this concentration.45'72 Work becomes difficult, but
not impossible, in the concentration range of 15,000 to 75,000
ug/m3 (10 to 50 ppm), ' and irritation of the throat mem-
branes has been reported at exposures of 50,000 (j.g/m3 (35 ppm).87
Work becomes impossible at levels above 75,000 (jg/m3 ,72 and
exposure to levels of 75,000 to 150,000 [ig/m3 (50 to 100 ppm)
cannot be tolerated, by humans for longer than 60 minutes. 44,45,52
*Conversion factor used in this report: 1 ppm is approxi-
mately equal to 1,470 ug/m3.
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Exposure for only a few minutes at 1,300 to 2,000 ppm may be
lethal;52/87 the acid neutralizes the alkali of the tissues
and causes inflammation of the upper respiratory tract, pul-
monary edema, or laryngeal spasm, with death possibly resulting.
Mists of hyd.rochloric acid, are not as dangerous to humans
as hydrogen chloride gas because the acid has no strong dehy-
d.rating effect on the tissues.^7 However, acid mists from
heated metal-pickling solutions may cause bleeding of the nose
and gums, ulceration of the nasal and oral mucosae, and tender-
ness of the facial skin so that shaving becomes painful.45 A
study conducted by Toyama et al..112 of an electrical appliance
factory indicated that people not accustomed to hydrochloric
acid mists showed a 9 percent decrease in the pulmonary venti-
latory peak flow rate when exposed for 1 hour to hydrochloric
acid mists (6 |_i in d.iameter), whereas the workers exhibited no
change.
Prolonged, exposure to low concentrations of hydrochloric
acid causes erosion of the teeth. -> However, there are no known
systemic effects, either acute or chronic, from inhalation of
hyd.rochloric acid or hydrogen chloride.- ' °'
The effects of hydrogen chloride on humans are summarized
in Table 3 in the Appendix.
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2.1.2 Sensory Thresholds
The odor perception threshold values for hydrochloric
acid given in the literature include 100 to 200 |-ig/m3 (0.067 to
0.134 ppm), 28'29 1,500 to 7,500 iag/m3 (1 to 5 ppm),45 and 14,700
Hg/m3 (10 ppm).105
Elfimova28'29 has studied the threshold reflex of the
eyes, respiratory action, and vascular reaction upon exposure
to hydrochloric acid aerosols. The results are summarized in
Table 3 in the Appendix.
2.1.3 Synergistic Effects
Stayzhkin85'102 investigated the effect of chlorine and
hydrogen chloride gas mixtures on man. In his study of the odor
threshold, the effect on reflex reactions of eye sensitivity
to light and of optical chronaxy were examined. His results
indicated that the two gases acted in combination in an
additive manner to produce a perceivable odor when neither gas
could be detected alone. The effect is expressed by the following
relationship where X must equal one or greater to have a
perceivable odor:
x _ Concentration Clp + Concentration HC1
Odor threshold C12 Odor threshold HC1
Furthermore, the physiological and neurological effects of the
mixtures were also in the nature of arithmetical summation.
2.2 Effects on Animals
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2.2.1 Commercial and Domestic Animals
No reports were found in the literature describing
injury to domestic, commercial, or wild animals from exposures
to hydrogen chloride or hydrochloric acid in rural or urban
environments or near factories that produce or use the acid.
2.2.2 Animal Experiments
Mackle et_ _a_l_.69 exposed one monkey, three rabbits, and
three guinea pigs to 50,000 ug/m3 (33 ppm) of hydrogen chloride
for a period of 4 weeks (6 hours per day, 5 days per week).
None of these animals exhibited immediate toxic effects or
pathological changes. However, the authors commented that
inhalation of hydrogen chloride daily for one month at 50,000
l_ig/m3 (33 ppm) may be dangerous. Rabbits and guinea pigs were
not killed at a concentration of 100,000 ug/m3 (67 ppm) for 5
days (6 hours per day). However, it was noted that the guinea
pigs were more sensitive to irritant properties of hydrogen
chloride than the rabbits, but the rabbits exhibited more pul-
monary and nasal damage than the guinea pigs. At higher con-
centrations, repeated exposures resulted in a weight loss that
was proportional to the degree of exposure. A concentration of
1,000,000 ug/1™3 (670 ppm) of hydrogen chloride for 2 to 6 hours
was lethal to rabbits and guinea pigs. Furthermore, 30 minutes'
exposure at approximately 6,400,000 ug/m3 (4,300 ppm) was lethal
to all the animals. At these concentrations, hydrogen chloride
causes necrosis of the tracheal and bronchial epithelia and also
pulmonary edema, atelectasis, emphysema, and pulmonary blood
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vessel damage. ' Production of lesions in the liver and
other organs by hydrogen chloride is also described. "
After Lehmann°4 exposed cats, rabbits, and guinea pigs
to 150,000 to 210,000 ug/m3 (100 to 140 ppm) of hydrogen chlo-
ride for 6 hours, he found slight corrosion of the cornea and
upper respiratory irritation in the animals. Clouding of the
cornea occurred after exposure to a concentration of 2,000,000
|_ig/m3 (1,350 ppm) for approximately 90 minutes. After approxi-
mately the same exposure time to a concentration of 5,000,000
M.g/m3 (3,400 ppm), death occurred in 2 to 6 days.
Leitz -* found that when the respiratory rate is increased
by an elevation in environmental temperature, the amount of
hydrogen chloride absorption is also increased, thereby height-
ening the danger of exposure to low concentrations.
Table 4 in the Appendix summarizes the reported effects
of hydrogen chloride inhalation by animals.
2.3 Effects on Plants
2.3.1 Phytotoxicity
Haselhoff and Lindau studied the effects of hydrogen
chloride and hydrochloric acid on plants after an incident in
which plant life was damaged near a factory manufacturing
alkali (see Section 2.3.2). Their studies demonstrated that
damage to plants from hydrogen chloride resulted from the direct
action of the gas itself on the above-ground parts of the plants
and not from the conversion products produced in the soil. Fumi'
gation experiments with viburnum and larch seedlings indicated
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8
that approximately 7,500 to 30,000 ug/m3 (5 to 20 ppm) of
hydrogen chloride could kill the plants within 2 days. More-
over, after 1 day at this concentration, the viburnum leaves
remained rolled up at the edges, withered, shrunk, faded, and
necrotic, even after they were placed in fresh air. Similar
injuries resulted from chlorine gas, but a higher concentration
of 750,000 i-ig/m3 (500 ppm) was necessary to produce damage.
Hydrochloric acid fumes (approximately 6 percent acid) required
only a few hours to damage the plants, primarily producing bleached
spots on the tips or margins of the leaves. At low concentrations
of hydrochloric acid (approximately 1 to 10 percent acid), the
plants remained healthy for several days.
Further experiments showed that a 1-hour exposure to
1,500,000 |-ig/m3 (1,000 ppm) hydrogen chloride produced local
lesions in fir, beech, and oak leaves. Marginal leaf scorch
was found on the leaves of maple, birch, and pear trees exposed
to hydrogen chloride. Tipburn of the fir needles resulting from
two exposures to 1,500,000 ag/m3 (1,000 ppm) was still visible
3 weeks later. The experiments also indicated that spruce was
not visibly affected at daily 1-hour exposures to 3,000,000
ug/m3 (2,000 ppm) hydrogen chloride for 80 days. However,
recent studies by Lacasse^l showed that spruce seedlings died
from exposure to less than 50 ppm of hydrogen chloride for only
20 minutes.
Hydrogen chloride injury in broad-leaf plants is indi-
cated by a marginal leaf burn that progresses basipetally with
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9
prolonged exposure .^2 In grasses, the tips become brown-
colored after exposure to low concentrations. The threshold
concentration for plant marking was suggested to be generally
75,000 to 1,500,000 ng/m3 (50 to 100 ppm) hydrogen chloride,
but these values were obtained with no air circulation over
the plants. Thomas107 found that the marking threshold for
sugar beets was a few hours' exposure at 15,000 i-ig/m3 (10 ppm).
Lacasse _et_ aJ^.62,74,93 have recently studied the effects
of low concentrations of hydrogen chloride on plants. Tomato
plants were exposed to 7,500 ng/m3 (5 ppm) hydrogen chloride
for 2 hours at 31°C, with a relative humidity between 65 and
75 percent, and a light intensity of 3.9 X 104 ergs/cm2-sec.
The leaves developed interveinal bronzing and bleaching, fol-
lowed by necrosis, within 72 hours after exposure. The middle-
aged leaves were affected more severely than the younger leaves.
Furthermore, the hydrogen chloride-exposed plants contained 300
percent more chloride than the unexposed control plants. The
immature leaves showed the greatest increase in chloride, while
the roots and stems showed little or no significant increase.
The increase in chloride was not found beyond 24 hours. In
fact, there was a slight decrease in chloride content after
the first 24 to 72 hours.
Experiments were also conducted to determine the thresh-
old for visible damage of 12 species of coniferous and broad-
leaf seedlings. "74 ip-^g experimental conditions were as follows:
exposure to 4,500 to 64,500 |-ig/m3 (3 to 43 ppm) hydrogen chloride
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for 4 hours at 27°C, relative humidity between 78 to 85 percent,
and light intensity of 1.4 X 104 ergs/cm2-sec. A summary of
the threshold values determined by these experiments is given
in Table 5 in the Appendix. The results indicate that the
coniferous plants were more resistant to incipient injury than
the broadleaf plants. Symptoms found in the broadleaf plants
included marginal and interveinal necrosis and necrotic flecking.
The only symptom observed for the coniferous species was tip
necrosis. The period of time for the first appearance of injury
varied between 8 and 24 hours.
Lacasse^2 found that the relative humidity of the sur-
rounding area is a very important factor in the damage to plants
exposed to hydrogen chloride. Thus, when the relative humidity
was increased from 40 to 65 percent, the rate and severity of
damage was observed to suddenly increase.
Thomas reported in 1951 that hydrogen chloride is less
toxic to plants than sulfur dioxide. Plant responses at high
concentrations of hydrogen chloride may resemble acute sulfur
dioxide injury.
A summary of the reported effects of hydrogen chloride
on plants is given in Table 5 in the Appendix.
2.3.2 Incidents of Plant Damage
Hindawi ° reported recently that emissions from a glass
manufacturing factory injured shrubs, trees, and plants in the
surrounding area. Specimens severely injured included maple
and cherry trees, rose bushes together with the buds, and begonias,
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Factory stack emissions analyzed after the incident contained
178,500 to 709,500 |ag/m3 (119 to 473 ppm) hydrochloric acid
and 1,560 to 2,760 |Jg/m3 (0.52 to 0.92 ppm) chlorine. Analy-
sis of injured silver maples showed a chloride content of
4,700 ppm, compared to 3,800 ppm for uninjured silver maple
trees.
Although no other incidents in the United States have
been reported, several other countries have reported damage
to plants from exposures to hydrochloric acid. The best-known
case happened in England. °7 Extensive damage to plants occurred
near a factory that used the Leblanc soda process to make alkali
and emitted hydrogen chloride as an unwanted by-product. Between
1836 and 1863, scrubbers were installed at various alkali factories
which removed 95 percent of the hydrogen chloride in the emis-
sions so that less than 450 ng/m3 (30 ppm) of hydrogen chloride
remained in the stack effluent. This control eliminated the
plant damage.
Bohne13 reported two examples of damage to plants by emis-
sions of hydrogen chloride from incinerators of nearby hospitals.
These incinerators were burning 80 to 90 percent paper and card-
board packing material. In one case, incineration for only 2 to
3 hours per day, 5 days a week, completely ruined the plants in
a nursery located 450 meters from the incinerator.
2.4 Effects on Materials
In the literature reviewed, no information was found de-
scribing corrosion or damage to materials from exposure to
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environmental concentrations of hydrochloric acid. However,
it is well-known that hydrochloric acid mists and solutions
are extremely corrosive to most metals and alloys.49,75
Mellor^S has summarized 24 studies on corrosion of various
forms of hard and mild steel and cast iron by hydrochloric
acid. He noted that corrosion of cast iron and steel increases
regularly as the concentration of the acid increases.
2.5 Environmental Air Standards
The American Conference of Governmental Industrial Hygien-
ists (ACGIH) has adopted 7,000 ug/m3 (5 ppm) as the threshold
concentration for hydrogen chloride for an 8-hour day, 5-day
week .HI
West Germany has also established 5 ppm as the permis-
sible work-station concentration. 5 West Germany has also
established an ambient air quality standard of 0.5 ppm (approxi-
mately 700 Ug/m3 ) of hydrogen chloride for a 30-minute mean
average, with a maximum of 1.0 ppm (1,400 ug/m3) of hydrogen
chloride for a 30-minute mean average. 5
Russia has established 15 ug/m3 (0.009 ppm) as a 24-
hour maximum average for ambient air concentration of hydrogen
chloride and a maximum of 50 Ug/m3 of hydrogen chloride (0.03
ppm) for a single exposure.^5,73. The standard for a 24-hour
average is below the concentrations which might cause reflexive
reaction of the sensory organs.
Czechoslovakia has established a maximum ambient air con-
centration which is different from that of Russia. The 24-hour
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mean was set at 0.02 ppm, with a one-time exposure maximum of
0.07 ppm.84
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3. SOURCES
Hydrochloric acid may be emitted from a wide variety
of sources. Emissions from some sources may go unnoticed
because the hydrochloric acid is generated as an unpredicted
product. The sources may be classified as follows:
(1) Direct manufacturing of hydrochloric acid (e.g.,
acid-salt and synthesis processes),
(2) A predicted by-product of a chlorination process
in indirect manufacturing (e.g., by-product process),
(3) Unpredicted or undesired product of a manufacturing
process (e.g., thermal decomposition of chloride-containing
reactants or products),
(4) Use of hydrochloric acid in the production or manu-
facturing of other products (e.g., pickling of metals),
(5) Burning or combustion of chloride-containing materials
(e.g., fossil fuels, plastics, paper),
(6) Heating of chloride-containing materials (e.g.,
heating of organic matter).
The first two are described in Section 3.2 as production
sources. The fourth source is discussed in Section 3.3 as a
product source. Those remaining are discussed in Section 3.4
as other sources.
In a study' of air contaminant emissions in Niagara
County, N.Y., it was found that 4,083 tons of hydrogen chloride
were emitted into the atmosphere per year. Of this total, 2,911
tons originated from processing plants and 1,172 tons from the
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15
consumption of coal and oil for heating purposes. Table 6 in
the Appendix lists the total emissions by urban areas within
the county-
3.1 Natural Occurrence
Natural occurrences of hydrochloric acid are rare.
Almost all of this acid, particularly as an atmospheric pollu-
tant, is produced by man, either from manufacturing processes
or burning or heating of chloride-containing substances. Minute
quantities of hydrochloric acid are present in nature in volcanic
fumes and in some rivers. 58 Qf course, it is also present in the
gastric juices of the body.
3.2 Production Sources
In the United States, hydrochloric acid is produced by
three processes:7'50'106 (1) the by-product process from
chlorination of organic compounds, (2) reaction of chloride
salt with sulfuric acid, and (3) synthesis via reaction between
chlorine and hydrogen gas. In 1934, 86 percent of the production
of hydrochloric acid was by the salt-acid process, 14 percent by
the synthesis process, and none from the by-product process.91
However, in recent years, the by-product process has become the
major production source, accounting for over 84 percent of the
hydrochloric acid production in 1967.23 This process has also
shown a continuing growth pattern (see Table 7 in the Appendix).
In contrast, the other two processes have shown very little
increase over the past few years. A more detailed description
of these processes can be found in other references.7'58'88'106
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16
According to 1962 data,88 60 plants use the by-product
process, 22 plants use the synthesis process, and 15 plants use
the salt-acid process. However, there are a total of only 88
plants producing hydrochloric acid, since some plants use more
than one process. Production by State and process is given in
Table 8 in the Appendix. The major producers of hydrochloric
acid are listed in Table 9 in the Appendix.
3.2.1 By-Product Process
The major commercial source of hydrochloric acid is the
chlorination of organic compounds by chlorine gas. Thus, in
any manufacturing process in which chlorine gas is used to
replace hydrogen with chlorine in a compound, hydrogen chloride
is produced as a by-product. Examples of such processes are
the preparation of carbon tetrachloride using methane (Equation 1)
and of chlorobenzene using benzene (Equation 2). The chlorination
process may be used to prepare a desired end product, such as
carbon tetrachloride or chlorobenzene, or may be used to pre-
pare an intermediate for a non-chloro-containing end product,
as in the preparation of phenol from benzene using chlorobenzene
(Equations 2 and 3).
CH4 + 4C12 > CC14 + 4HC1 , . ,
(Methane) (Carbon tetrachloride) t^uation j.;
CsHs + Cla > CSH5C1 + HC1 (Rmiatinn 7)
(Benzene) (Chlorobenzene) liquation 2)
CSH5C1 + NaOH > C6H5OH + NaCl (Fnn^inn ^ >
(Chlorobenzene) (Phenol) (Equation 3)
Therefore, it is not possible to determine from the end products
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17
of a company whether by-product hydrochloric acid is being
produced if one is not familiar with each of the processes
used to obtain the final product. Numerous chlorinated and
nonchlorinated organic compounds are made in which hydrogen
chloride is evolved as a by-product. In fact, approximately
70 percent of the chlorine produced today is used in the manu-
facture or preparation of organic compounds. The ever-
increasing use of chlorinated organic compounds is reflected
in the production of hydrochloric acid using by-product
recovery (see Table 7 in the Appendix).
The effluent gas from the chlorination of an organic
compound contains not only hydrogen chloride but also various
amounts of air, chlorine gas, and organic products, depending
on such factors as initial organic reactant and conditions
used. Therefore, the recovery system for the hydrogen chlo-
ride or hydrochloric acid varies with the nature of the other
impurities present in the effluent gas. For example, if the
organic contaminants are low-boiling, the hydrogen chloride
is removed first by means of a water absorption system (see
Section 4). On the other hand, if the organic impurities are
high-boiling, they are removed by condensation before the hydro-
gen chloride is absorbed. To obtain anhydrous hydrogen chloride,
the effluent gas is fed into a condenser or distillation appa-
ratus for separation of the different products. Several recovery
systems are reported in the literature.16'47'63'77'98 Normally,
the hydrochloric acid produced by this method contains organic
impurities and may require further purification.
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18
Although hydrochloric acid produced as a by-product is
collected for use and sale by some companies, in other cases
the acid emissions may only be treated to avoid air pollution;
and in still others, nothing may be done about the emissions.
3.2.2 Salt-Acid Process
In this process, common salt (sodium chloride, NaCl)
is reacted with sulfuric acid (60° or 66° Baume). The reac-
tion takes place in two steps: first, hydrogen chloride and
sodium acid sulfate are formed, and second, sodium acid sul-
fate is further reacted with sodium chloride to yield more
hydrogen chloride and sodium sulfate (normal sulfate). (See
Equations 4 and 5.) In cases in which sodium acid sulfate is
available—-e.g., as a by-product in the manufacture of nitric
acid—the acid sulfate is used directly as shown in Equation 5.
NaCl + HSS04 »NaHSO4 + HC1 (Equation 4)
NaHSO4 + NaCl »Na2SO4 + HC1 (Equation 5)
Generally, the salt and a slight excess of acid are
heated to 1,400 to 1,600°F in a Mannheim oven. The reactants
are continuously fed into the center of the furnace, and the
salt cake that forms is removed at the periphery, where it is
discharged continuously through a chute for transfer to storage,
The effluent gas contains 30 to 70 percent (by volume) hydrogen
chloride, as well as salt dust, air, and small traces of chlo-
rine. This gas is passed through dust removal equipment, such
as settling chambers or cyclones, and then cooled to approxi-
mately 100°F by means of tube coolers or packed towers.50,58
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19
A further purification system, usually coke filtering, is
used to remove sulfuric acid mist and the remaining fine dust
particles. After this final step, the hydrogen chloride is
collected by absorption methods described in Section 4.
One of the major producers of hydrochloric acid in
the United States uses the Hargreaves process.58,92 jn this
process the salt, sodium chloride, is reacted directly with
sulfur dioxide in the presence of steam and air (Equation 6).
The sulfur dioxide, obtained by burning sulfur, is passed
into a series of vertical chambers which have perforated trays
for the salt. The system is designed so that the sulfur diox-
ide stream is first passed through a chamber containing nearly
spent salt and lastly through a chamber containing the raw
salt. The system temperatures vary from 1,000°C initially to
800°C in the final chambers of raw salt. The end gas then is
passed through the absorption system to obtain the hydrochloric
acid.
4NaCl + 2S02 + O3 + 2H20 >2Na3SO4 + 4HC1 (Equation 6)
Hydrogen chloride emissions from the salt-acid process
are higher than those from either of the other two processes.
In the Mannheim furnace operations, losses of hydrogen chlo-
ride can occur through leaks at the furnace, removal of hot
salt cake, or from the tail gas emissions. 1' ^2 jn ^he more
modern furnaces, emissions are controlled by use of an exhaust
fan installed after the absorber system to maintain the pres-
sure slightly below atmospheric level at the furnace; the hot
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20
salt cake is also precooled in a water-cooled screen conveyor
before dumping. However, if large leaks occur in the system,
the system becomes blocked, or the exhaust fan fails, the
furnace can lose its draft, and emissions into the atmosphere
can occur around the furnace, particularly at the doors and
at the salt cake discharge. -*0 Short periods of emissions
can occur if the furnace door is opened to break up large
lumps of salt that interfere with proper operation of the
furnace.
Emissions resulting from upsets in the hydrogen chlo-
ride absorption system, which is common to all three processes,
are discussed in Section 4.
3.2.3 Chlorine-Hydrogen Synthesis
The advantage of the chlorine-hydrogen synthesis process
is that a hydrochloric acid is produced that is very pure,
depending on the purity of the reactants. In this process,
chlorine is burned in a slight excess of hydrogen in a reac-
tor or combustion chamber.50,106 T^Q resulting product is
98 to 99,7 percent pure.106 Since a mixture of hydrogen and chlo-
rine is explosive, several safety provisions are incorporated
into the system, which is completely enclosed. Thus, there is
very little emission of hydrogen chloride in this process.
The product gas is passed through a gas-cooling system and then
an absorption system similar to that used for the salt-acid
process to give hydrochloric acid. If hydrogen chloride is
desired, only gas-cooling equipment is necessary-
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21
3.3 Product Sources
Hydrochloric acid and hydrogen chloride have a wide
variety of uses;58'^6 major uses are in the manufacture of
organic and inorganic chemicals, production of metals, the
cleaning of metal and other materials, food processing, and
acidification of oil wells. The consumption of hydrochloric
acid for these uses in 1963 is given in Table 10 in the Appen-
dix. The consumption by certain industries for 1958 and 1963
is given in Table 11 in the Appendix. As shown by the latter
table, the demand for hydrochloric acid is increasing (see also
Table 7, Appendix). The use of hydrochloric acid in steel pick-
ling, vinyl plastics, oil well acidizing, and industrial cleaning
and chemical products is also increasing.
However, even with the growing demand, there has been an
oversupply of hydrochloric acid in recent years.58'88 This fact,
plus the increase in stream pollution by the acid, has made dis-
posal of hydrochloric acid an expanding problem. One possible
solution for the oversupply problem is the use of hydrochloric
acid to manufacture chlorine.58 According to reports by trade
sources, the oversupply has shown a gradual decline.20
3.3.1 Manufacture of Chemicals
Nearly half of the hydrochloric acid produced is used in
the manufacture of organic chemicals, such as chlorinated organic
compounds, including the manufacture of alkyl chlorides from
olefins and chlorides from alcohols. It is also used in
the presence of oxygen (oxyhydrochlorination) to prepare
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22
polychlorinated alkyl compounds and chlorinated aromatic
compounds. Other uses occur in the production of dyes and
dye intermediates and in the preparation of pharmaceutical
chemicals, such as various amine hydrochloride salts, aconi-
tic acid, adipic acid, and citric acid. In the production
of chlorinated polymers, hydrochloric acid is used in the
preparation of intermediate monomers, such as chloroprene
and vinyl chloride. In addition, it is used as a solvent
and a catalyst in organic reactions involving isomerization,
polymerization, and alkylation.
Only about 5 percent of the hydrochloric acid pro-
duced is used for preparing inorganic chemicals, such as
metal chlorides, alumina, phosphoric acid, titanium dioxide,
silica gel, and paint pigments.58'76'88'96 Recently, hydrochloric
acid has been used to manufacture chlorine by electrolysis or
oxidation methods.
3.3.2 Metal Production
Metal production consumes approximately 17 percent of
the hydrochloric acid produced. It is used in many metallur-
gical extraction processes for treating various high-grade
ores, including those which yield germanium, manganese, radium,
tantalum, tin, and vanadium. Hydrochloric acid is also being
considered as a substitute for sulfuric acid in treating low-
grade ores. The Dron process for obtaining magnesium from
seawater uses hydrochloric acid. This acid is also used as
an etching medium for chemical milling of metals such as alu-
minum, magnesium, steel, and titanium.
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23
3.3.3 Other Uses
Another major use, accounting for approximately 18 per-
cent of the production of hydrochloric acid, is in the Dowell
process for activating petroleum wells. Inhibited hydrochlo-
ric acid is used to improve oil well porosity and well flow
or production by acidizing the formation.
Approximately 7 percent of the hydrochloric acid pro-
duced is used primarily for pickling and cleaning metal prod-
ucts and removing oxides and scale from boilers and heat-
exchange equipment.
A small amount of hydrochloric acid is used in food
processing, including hydrolysis of proteins and starch in
the preparation of dextrose and starch syrups, manufacture
of monosodium glutamate, and reactivation of bone char and
charcoal in sugar refining.
It is also used in chlorinating and reclaiming rubber,
coagulating latex, fluxing babbitt metals, detanning hides
following depilation, and etching airport runways in prepara-
tion for resurfacing with bonded concrete. It is also an
ingredient in tanning and dye liquors.
3.4 Other Sources
Atmospheric emissions of hydrochloric acid result from
a large number of sources other than the manufacture and use
of this acid. These other sources include heating or burning
of chloride-containing materials in the presence of organic
compounds or other hydrogen-containing substances. Chlorides
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24
are also widespread in nature and in many natural products.
Moreover, many manufactured products contain chloride, such
as polyvinyl chloride plastics. When these materials are
burned, incinerated, or perhaps just heated, hydrochloric
acid can be evolved as a predicted or unpredicted product.
The examples discussed in this section give an indication of
some of the possible emission sources.
3.4.1 Coal
Burning coal may be one of the major contributors to
hydrochloric acid air pollution. Chlorine is present in coals,
mostly in the form of inorganic chloride salts27 that are solu-
ble in water.22 when coal burns, most of the chloride salts
are converted to hydrogen chloride,^'*^° which is then emitted
into the atmosphere.
Analysis of United States coals shows that the chlorine
content ranges from 0.01 to 0.56 percent.I/51'78»89 Table 12
in the Appendix indicates the chlorine content of some
selected coals in the United States. The Central and Appala-
chian areas, which have high-chlorine-content coals, are also
the areas which consume most of the coal for heat and energy.51
Piper and Van Vliet8^ found that in burning coal con-
taining 0.066 percent chlorine, 49 ppm of hydrogen chloride
were emitted at the stack, meaning that 60 percent of the
chlorine originally in the coal was converted to hydrogen
chloride. lapalucci, Demski, and Bienstock^l performed
experiments with pulverized coal containing 0.1 to 0.4 percent
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25
chlorine at carbon combustion efficiencies of 94 to 98 per-
cent. Under these conditions, they found that 93 to 98
percent of the chlorine was emitted as hydrogen chloride
and the remainder left in the ash. To verify these results
under actual conditions, the stack of a local power plant
was sampled after burning a bituminous coal containing 0.087
percent chlorine,, Analysis showed that only 1.5 percent of
the chlorine was retained in the ash, and the balance was
emitted in the stack gas as hydrogen chloride.
Furthermore, the amount of hydrochloric acid pollution
by burning coal may be increased when calcium chloride is
added to the coal as an antifreeze or dust-proofing agent.53
A potentially large amount of hydrochloric acid pollu-
tion may result from coal burning. For example, it is esti-
mated that 671 million short tons of bituminous coal will be
consumed in 1975.H Assuming that the average chlorine con-
tent of the coal is 0.2 percent and that 95 percent of this
is converted to hydrochloric acid, then approximately 1.3
million short tons of hydrochloric acid will be produced
from coal burning in 1975. For comparison, manufacture of
hydrogen chloride and hydrochloric acid was 1.6 million short
tons in 1967. 3 lapalucci, Demski, and Bienstock^l estimated
on a similar basis (i.e., 0.2 percent chlorine coal) that an
800-MW power plant will emit from the stack 11,300 standard
cubic feet of hydrogen chloride each hour, or 4,560 tons each
year.
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26
3.4.2 Fuel Oil
Fuel oils contain small amounts of chlorides and can
therefore emit hydrogen chloride when burned. A recent study
on fuel oils cited two 1938 reports on chloride emissions.
In one report-^-® the chloride content of the ash was given as
0.1 and 4.6 percent by weight for oils found in Kansas and
Texas, respectively. The other report-^-^ indicated that the
maximum hydrogen chloride content in emissions was approxi-
mately 46 ppm in the stack gas, or approximately 1 pound per
1,000 pounds of oil. It has been reported that 500 pounds
of hydrogen chloride per day per 100,000 persons is produced
by using oil for domestic heating.30 in comparison, the value
is four times higher for domestic heating using coal.
3.4.3 Automobile Exhaust
Gasolines which contain tetraethyl lead (TEL), tetra-
methyl lead (TML), or other lead additives also usually con-
tain ethylene chloride or ethylene bromide. These organic
halide compounds are used as lead scavengers; that is, these
halides will react with the lead to form volatile lead halides
which can be emitted with the exhaust gases and, therefore,
prevent lead deposits in the automobile engine. An example
of an additive mixture for gasoline is given in Table 1.
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27
TABLE 1
"ETHYL" ANTIKNOCK COMPOUND-TEL MOTOR 33 MIX101
Weight
Compound (percent)
Tetraethyl lead 57.5
Methyl cyclopentadieny-
manganese tricarbonyl 7.0
Ethylene dibromide 16.7
Ethylene dichloride 17.6
Other (dye, inerts) 1.2
During gasoline combustion, hydrogen chloride or hydro-
chloric acid can form and be emitted into the air. Rose ^
feels that hydrochloric acid is present in automobile exhaust
but did not know of any quantitative data available. He men-
tioned that the exhaust condensates were very acidic, about
pH 2.
3.4.4 Burning of Chloride-Containing Plastics
Several of the plastics used today contain organically
bound chlorine; examples of some of the more common ones are
polyvinyl chloride (approximately 57 percent chlorine), poly-
vinylidene chloride (approximately 73 percent chlorine), and
neoprene (approximately 40 percent chlorine). In addition,
organic chlorides are added to other types of plastics and
materials as fire-retardants. Chloride-containing plastics
are used in making plastic films, containers, seat covers,
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28
wire insulation, and many other materials. When these chlo-
ride plastics are heated or burned, hydrogen chloride is
evolved.12'18'54,71,81 studies have been conducted with poly-
vinyl chloride films12'81 to determine the type and quantity
of gases evolved. In one investigation,12 a sample was heated
at a rate of 3°C per minute; upon reaching 280°C a rapid
weight loss started and continued until about 300°C. During
this period a 60 percent weight loss was found, and analysis
showed that almost all the chloride had been evolved as hydro-
gen chloride. In another study,81 it was found that hydrogen
chloride evolved at 100°C; moreover, the rate of evolution
depended on the length of the heating period. The rate of
hydrogen chloride evolution for 1 hour at 100°C was 8,000
|ag/m3 ; after 2 hours, 12,000 |ag/m3 ; and after 3 hours, 20,000
|_ig/m3 •
Thus, open burning or incineration of chlorinated plas-
tics is a probable source of hydrochloric acid pollution.
Without effective control measures, this problem will inten-
sify with the increased use of plastics projected for the
future.
3.4.5 Burning of Paper Products
Analysis of paper products indicates that the chloride
content is low,10*'13 approximately 0.03 to 0.16 percent by
weight. Nevertheless, two examples cited in the literature
demonstrate that the amounts of hydrochloric acid emissions
from the incineration of paper can cause injury to plants.13
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29
In both examples (see Section 2.3.2), the plant injury was
caused by hydrochloric acid emissions from a hospital incin-
erator burning trash consisting of 80 to 90 percent paper
products. Additional studies indicated that 53 to 95 percent
of the chloride in paper products is lost on heating at 900°C.
3.4.6 DDT Production
DDT (dichlorodiphenyltrichloroethane) is a common pesti-
cide manufactured from chloral, chlorobenzene, and sulfuric
acid2 (see Equation 7).
H2SO4
CClgCHO + 2CSH5C1 » CC13CH(C6H4C1)2 + HSO
(Chloral) (Equation 7)
As seen from the reaction equation, hydrochloric acid is nei-
ther a reactant nor a product of the desired reaction. How-
ever, the primary contaminate in the emissions is hydrochloric
acid from decomposition of chloral. The total amount of ef-
fluent gases has been estimated as about 1 percent of the
weight of DDT produced.
This is an example of a manufacturing process in which
hydrochloric acid is considered neither a reactant nor a prod-
uct but, nevertheless, is part of the effluent gas stream.
In this case, the hydrochloric acid emissions are due to the
decomposition of the chloride compounds used in the reaction.
3.4.7 Lemon Pulp Extraction
One company has reported on the extraction of lemon pulp
with isopropyl alcohol at 120°F. Besides the predictable
emissions of the alcohol, the effluent vapor also contained
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30
hydrochloric acid droplets. In this case, the company was
aware of the content of the emissions and used an appropriate
treatment system to control the emissions.
Although probably only a very minor source, this repre-
sents an example of the heating of organic matter at a low
temperature (120°F) with the evolution of small quantities
of hydrochloric acid.
3.5 Environmental Air Concentrations
No information has been found on environmental air con-
centrations of hydrochloric acid. However, Gorham40 observed
that in Great Britain, precipitation samples from urban areas
exhibited a distinct correlation between chloride content and
acidity in samples of pH less than 5.7.
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31
4„ ABATEMENT
The high solubility of hydrogen chloride in water and
the low vapor pressures of even 20 percent hydrochloric acid
solutions make collection of hydrogen chloride in water an
effective and inexpensive method of control.
Thus in the manufacture of hydrochloric acid (or hydro-
gen chloride)/ the emission control system, which is also part
of the system for obtaining hydrochloric acid from the hydro-
gen chloride, consists mainly of water absorption facilities.
Different types of absorbers are used, but the systems gen-
erally consist of a packed tower or a cooling absorption
tower followed by a packed tail tower .->0 ' 58f106 r^e pac;keci
tower systems-^-58 normally include a connected set of S-
bend tubes, followed by one or more towers in series. Cold
water is added at the last or tail tower and flows over into
the previous tower. The concentration of hydrochloric acid
in this water is thus increased from tower to tower until
it reaches the S-bend tubes, where the acid solution attains
its final strength. However, the packed tower systems are
rapidly being replaced by cooled absorption systems because
the latter are more efficient, economical, and compact. The
cooled absorption tower designs may consist of either a
countercurrent or co-current flow of gas and water. One type
uses water-jacketed packed tantalum towers with countercurrent
flow. The most common system is the co-current falling film
absorbers.49,58,59 jn this system, gas and weak acid solution
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32
from the packed tail tower flow downward over vertical,
water-cooled, wetted-wall columns. Where anhydrous chloride
is the desired product, absorption systems are not used.50
It has been reported that the use of water scrubbing
systems can reduce the emissions to less than 0.1 pound of
hydrogen chloride per ton of acid produced, although emis-
sions can be 30 times that amount with less effective equip-
ment.7 According to Faith et _al. ,31 hydrogen chloride
emissions can be reduced to a range of 0.1 to 0.3 percent
by volume by the use of two or more tail towers in series.
The emissions of hydrochloric acid may be high if an upset
occurs in the absorption system due to either improper tem-
perature control or insufficient feed water.106
Other systems that appear to be effective for the con-
trol of hydrochloric acid or hydrogen chloride emissions are
the rotary brush scrubber^ anc| the ejector venturi scrubber.
With the former system, collection efficiencies of 99.995 per
cent have been reported with an initial hydrogen chloride
content of 610 g/m3. In the latter system, scrubbing effi-
ciency as high as 99 percent has been given for a single-
stage unit for fumes containing up to 20 percent hydrogen
chloride. The high solubility of hydrogen chloride in water
accounts for the high degree of efficiency of these systems.
Dry solid adsorbents have also been studied for removal
of hydrogen chloride vapors.9'7! Adsorbents investigated
include chromium oxinate and basic salts36 such as Beralyme,
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33
soda lime, lithium carbonate, and silica-alumina mixtures.
Chromium oxinate or tris-(8-hydroxyquinolinato)chromium(III)
exhibited physical adsorption with anhydrous hydrogen chlo-
ride, but the adsorbing bed showed a tailing effect a long
time before the exit gas concentration reached the entering
concentration.
Studies by lapalucci, Demski, and Bienstock^l indicate
that hydrochloric acid emissions from coal burning can be
reduced by adding basic salts, such as sodium carbonate,
potassium carbonate, calcium carbonate, and dolomite. Chlo-
rine retention in the ash when a small amount of basic salt
was added was 8.8 to 37.8 percent, compared to 7.9 percent
without an additive.
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34
5. ECONOMICS
No information has been found on the damage costs or
economic losses due to the effects of hydrochloric acid air
pollution on humans, animals/ plants/ or materials. In
addition, no information has been found on the economic
costs of abatement (installation and operation costs of
control equipment and cost benefits of usable emissions).
Data on the production and consumption of hydrochloric
acid are presented in Section 3.
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35
6. METHODS OF ANALYSIS
All of the common methods of analysis for hydrochloric
acid in air depend upon (1) measurement of acidity, (2) mea-
surement of chloride ions/ or (3) combination of the two
measurements. Therefore, other strong acids (e.g., sulfuric
acid, nitric acid) or other chloride salts (e.g., sodium chlo-
ride) can cause serious interference.
6.1 Sampling Methods
In most methods, hydrochloric acid is collected in
impingers containing water.4'25'105 The high solubility of
hydrochloric acid in water yields excellent absorption effi-
ciency. 66
The results of one investigation indicate that certain
phosphate salts, particularly silver phosphate, have a high
collection efficiency for hydrochloric acid but do not absorb
sulfur dioxide.17 However, hydrobromic acid is also absorbed.
Preliminary studies indicate that liquid crystals may
make effective and selective collection materials for hydro-
chloric acid and other gaseous pollutants.33 Acid mists have
also been collected on paper,19 gelatinous film,38'68'114 thin
metal films,67 and metal-coated glass slides.43,48
6.2 Qualitative Methods
The presence of hydrochloric acid or any other strong
acid in air can be determined by passing the air over moist
pH indicators such as methyl orange, congo red, or blue lit-
mus papers. Hydrochloric acid or other chlorides can also
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36
tie detected by bubbling the air through water and adding
silver nitrate. Depending on the concentration of chloride,
the solution may show a slight turbidity, or yield a white
to grayish precipitate which will not change on addition of
nitric acid but will dissolve or disappear upon addition of
ammonia.
6.3 Quantitative Methods
In the absence of other strong acids, hydrochloric acid
samples which have been collected in water may be determined
quantitatively by the usual direct titration methods with
oc
standard bases.
A spectrophotometric method for determination of strong
acids has been reported. 9/0 After the air sample is passed
through water, methyl red is added to the acidic solution and
the optical density at 530 mp. is determined. Normal concen-
trations of carbon dioxide and 1,000 Pg of sulfur dioxide per
2
m of air do not interfere.
The size and quantity of acid mists have been deter-
mined by the use of both gelatinous films 38,68,114 an<^ metal-
coated glass slides.43'48 The latter method is not affected
by relative humidity. Through use of an electron microscope,
it is possible to detect acid droplets with diameters of less
than 0.1 p..48
In the absence of soluble chloride salts, hydrochloric
acid samples dissolve in water and may be determined by the
standard methods for chloride determination," including the
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37
Mohr method,99'100 absorption indicator method,32'60 and
the modified Volhard method. These methods have a sensi-
tivity of approximately 18,000 |jg of chloride per liter.
For very small amounts of chloride in air, the determination
can be made turbidimetrically or nephelometrically.2^'^9/"
The hydrochloric acid solution is treated with silver nitrate
and the turbidity determined spectrophotometrically; sensi-
tivity is in the microgram range. Recently, a method has
been developed for determining chloride colorimetrically. '
This method is based on the yellow color produced by the iron(IH)
chloro complex in perchloric acid with a sensitivity of
approximately 1,000 ng/m3 of chloride. This method suffers
from interference from mercury and sulfate ions and is af-
fected by the relative humidity of the air. There is a
neutron activation technique for determining chloride in
particulates with a sensitivity of approximately 0. 06 |j.g/m3 ,56
An automated analysis method for chloride is used by
the National Air Sampling Network.110 This method is based
on the reaction of chloride with mercury thiocyanate to yield
thiocyanate ions. Thiocyanate ions react with ferric ions to
form the stable red complex, hexacyanatoferrate ion, which can
be determined spectrophotometrically at 460 m[a. The relative
standard deviation for chloride is 1.0 _+ 0.1 |ag/mlo
Since air samples usually contain other acids as well
as chlorides, these methods are not generally applicable.
There are no methods available that are free from interference
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38
by all other possible pollutants. However, an air sample
containing a mixture of sulfur oxides, hydrochloric acid,
and other chlorides can be analyzed by combining the methods
reported in two papers.^'105 The air sample is passed through
an aqueous solution of hydrogen peroxide. The aqueous solu-
tion is then divided into three parts for three separate
analyses: sulfate, chloride, and hydrogen ion. From these
results the amount of each component can be determined.
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39
7. SUMMARY AND CONCLUSIONS
Hydrogen chloride reacts rapidly with the moisture in
the air and is generally found in the ambient atmosphere as
hydrochloric acid. The acid at low concentrations, 15,000
to 75,000 Lig/m3 (10 to 50 ppm) , irritates primarily the
mucous membranes of the eyes and upper respiratory tract in
both humans and animals. Prolonged exposures to low con-
centrations of hydrochloric acid can also erode the teeth.
Work is intolerable after more than 60 minutes in atmospheres
containing approximately 75,000 to 150,000 M.g/m3 (50 to 100
ppm) of hydrochloric acid. Higher concentrations (approxi-
mately 1,500,000 |~ig/m3 or 1,000 ppm) can attack the mucous
membranes, causing inflammation of the upper respiratory
system and resulting in pulmonary edema or spasm of the lar-
ynx, which can be fatal. A wide variety of plant life is
susceptible to the toxic effects of hydrogen chloride or
hydrochloric acid. Several examples of plant damage due to
hydrochloric acid emissions have been reported in the litera-
ture. The primary effect on plants is a discoloration or
bleaching of the leaves. The threshold for visible damage
was originally reported as 75,000 to 150,000 [ag/m3 (50 to
100 ppm) of hydrogen chloride. However, recent studies indi-
cate that the threshold for many plants is less than 10 ppm
for 4-hour exposures. The strong acidic properties of hydro-
chloric acid make it extremely corrosive to most metals.
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40
Some countries have established ambient air quality
standards for hydrochloric acid, including West Germany
(approximately 750 |ag/m3 or 0.5 ppm as a mean 30-minute
average) and Russia (approximately 15 \j.g/m3 or 0.009 ppm
as a 24-hour average).
The production rate since 1961 has shown a general
increase of approximately 9 percent. Hydrogen chloride is
produced by three main processes in the United States: acid-
salt, direct synthesis, and the by-product process from
chlorination of organic compounds. The latter process, the
major production source, has shown a steady increase. Many
organic chlorinating processes and other organic processes
involving chlorinated compounds may produce hydrogen chloride
as a by-product, but it may not be economically feasible to
recover the product for other uses. Hydrochloric acid is
produced by absorbing the hydrogen chloride gas into water.
Hydrochloric acid (or hydrogen chloride) is primarily
used to manufacture inorganic and organic chemicals, the
latter accounting for almost 50 percent of the production
in 1963. Other major uses include metal production, oil-
well acidizing, metal and industrial cleaning, and food pro-
cessing.
Another potential source of emissions of hydrochloric
acid is the heating or burning of chlorinated materials.
The burning of coal appears to be a possible major source of
hydrochloric acid pollution, since the chloride in coal is
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41
converted to over 90 percent hydrogen chloride during the
burning process. Similarly, the burning of chlorinated
plastics and paper can be an emission source, and possibly
the burning of fuel oil and gasoline as well.
No information has been found on the concentrations
of hydrochloric acid in the atmosphere. Hydrogen chloride
emissions from commercial processes can be effectively con-
trolled by the equipment that is available today. Systems
now in use include packed water scrubbing towers and cooled
absorption towers. Emissions from coal burning may be de-
creased by the addition of basic salts to the coal before
burning.
No information has been found on costs for the control
of hydrochloric acid pollution or for costs incurred by damage
to humans, animals, plants, and materials as a result of hydro-
chloric acid emissions.
No continuous monitoring methods are available for mea-
suring the hydrochloric acid content of environmental air.
The common methods used measure either the acidity or chlo-
ride content of the air sample, and therefore suffer from
interference from other acids and chlorides present in the
environmental air.
Based on the material presented in this report, further
studies are suggested in the following areas:
(1) Determination of the amount of hydrochloric acid
present in the atmosphere of heavily populated areas,
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42
particularly near the source of production and near coal-
burning establishments and incinerators.
(2) Evaluation of the effects of low concentrations
of hydrochloric acid on humans, animals, plants, and materials,
(3) Determination of the contribution of automobile
exhausts, incinerators, and other combustion sources to hydro-
chloric acid air pollution.
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43
REFERENCES
1. Abernethy, R. p., and F. H. Gibson, Rare Elements in Coal,
U. S. Bur. Mines Inform. Circ. 8163 (1963).
2. Air Pollution Control in Connection with DDT Production,
J. Air Pollution Control Assoc. 14 (3) :49 (1964).
3. Air Pollution—Niagara County (Comprehensive Area Survey
Report No. 3), New York State Air Pollution Control Board,
Albany, N.Y. (1964).
4. Alekseyeva, M. V., and E, V. Elfimova, Fractional Determina-
tion of Hydrochloric Acid Aerosol and of Chlorides in
Atmospheric Air, Giqiena i Sanit. 23 (8) :71 (1958).
5. Altman, P. L., and P. S. Dittmer, (Eds.), Environmental
Biology (Bethesda, Md.: Federation of American Societies
for Experimental Biology, 1966).
6. Atmospheric Emission from Chlor-Alkali and Related Manu-
facturing Processes, Joint National Air Pollution Control
Administration and Manufacturing Chemists' Association,
Inc. (To be published).
7. Atmospheric Emissions from Hydrochloric Acid Manufacturing
Processes, Joint National Air Pollution Control Administra-
tion and Manufacturing Chemists' Association, Inc. (To be
published).
8. Barnebey, H. L., Removal of Exhaust Odors from Solvent
Extraction Operation by Activated Charcoal Adsorption,
J. Air Pollution Control Assoc. 15 (9):422 (1965).
9. Berkau, E. E., G. T. Fisher, and M. M. Jones, The Influence
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-------
44
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49
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51
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-------
APPENDIX
-------
APPENDIX
TABLE 2
PROPERTIES OF HYDROGEN CHLORIDE AND HYDROCHLORIC ACID49'76
Properties
Color, odor, normal
state
Boiling point
Melting point
Hygroscopicity
Density
Heat of fusion
Heat of vaporization
Hydrogen Chloride
(HCl)a
Colorless gas, pungent,
irritating odor, fumes
in air
-85°C (-121°F)
-111°C (-168°F)
Very hygroscopic
1.6397 g/1 (0°C, 760 mm)
476-504.5 g-cal/mole
3860_+4 g-cal/mole
Hydrochloric Acid
(HC1, aqua)b
Colorless liquid; sometimes yellowish
due to impurities (iron, arsenic,
chlorine, and organic matter) ; pungent
and irritating odor
Aqueous solution containing 20
HC1: 110°C (230°F)
.24%
27.92% HC1: -42°C (-43.6°F)
37.14% HC1: -74°C (-101.2 F)
Hygroscopic
20.04% HC1: 1.1006 g/1
37.14% HC1: 1.1885 g/1
(continued)
Ul
-------
TABLE 2 (Continued)
PROPERTIES OF HYDROGEN CHLORIDE AND HYDROCHLORIC ACID49'76
Properties
Hydrogen Chloride
(HCl)a
Hydrochloric Acid
(HC1, aqua)b
Reactivity
Non-corrosive when dry.
Reacts rapidly with
organic materials
Highly corrosive to moist metals with
evolution of hydrogen gas. Reacts
with basic salts (metallic oxides and
carbonates)
Solubility in H30)
(g/lOOg H30)
82
67
63
,3 ( 0°C)
.3 (30°C)
,3 (40°C)
59.6 (50°C)
56.1 (60°C)
aAlso called hydrochloric acid, anhydrous.
Also called muriatic acid.
-------
APPENDIX
TABLE 3
SUMMARY OF REPORTED EFFECTS OF INHALATION OF HYDROGEN CHLORIDE BY HUMANS
Concentration
( ppm ) *
50-100
10-50
10
1,300-2,000
1,000-1,300
50-100
35
1,000-2,000
10
5
Exposure
Time
Few min
30-60 min
60 min
Effects or Comments
Work is impossible
Work is difficult but possible
Work is undisturbed
Lethal
Dangerous
Intolerable
Irritation of throat after short exposure
Brief exposures are dangerous
Irritation
No organic damage
Reference
45,72
45,72
45,72
52,103
52
35,44,52,87
87
87
113
113
Ul
(continued)
-------
APPENDIX
TABLE 3 (Continued)
SUMMARY OF REPORTED EFFECTS OF INHALATION OF HYDROGEN CHLORIDE BY HUMANS
Concentration
( ppm ) *
10
0.067-0.134
0.402
0.134
0.335
0.067-0.134
1-5
Exposure
Time
Effects or Comments
Odor threshold value
Odor threshold value
Concentration for threshold reflex effect
on optical chronaxie
Concentration for threshold reflex effect
on eye sensitivity to light
Concentration for threshold effect on
digito-vascular toxicity
Threshold concentrations of change in the
rhythm and depth of respiratory movement
Odor threshold value
Reference
105
28,29
28,29
28,29
28,29
28,29
45
*1 ppm = 1,470
at 25°C.
Ul
-------
APPENDIX
TABLE 4
SUMMARY OF REPORTED EFFECTS OF INHALATION OF HYDROGEN CHLORIDE ON ANIMALS
Species
Rabbits
Guinea pigs
Cats
Rabbits
Guinea pigs
Cats
Rabbits
Concentra-
tion (ppm)*
4,300
4,300
3,400
3,400
3,400
1,350
1,350
Exposure
Time
30 min
30 min
90 min
90 min
90 min
90 min
90 min
Effects or Comments
Fatal in some cases, due to
laryngeal spasm, laryngeal
edema, or rapidly developing
pulmonary edema
Fatal in some cases, due to
laryngeal spasm, laryngeal
edema, or rapidly developing
pulmonary edema
Death after 2 to 6 days
Death after 2 to 6 days
Death after 2 to 6 days
Severe irritation, dyspnea,
and clouding of the cornea
Severe irritation, dyspnea,
and clouding of the cornea
Reference
45,69
45,69
45,64
45,64
45,64
45,64
45,64
(continued)
-------
APPENDIX
TABLE 4 (Continued)
SUMMARY OF REPORTED EFFECTS OF INHALATION OF HYDROGEN CHLORIDE ON ANIMALS
Species
Guinea pigs
Rabbits
Guinea pigs
Rabbits
Guinea pigs
Rabbits
Guinea pigs
Concentra-
tion (ppm)*
1,350
670
670
300
300
100-140
100-140
Exposure
Time
90 min
2 hr
2 hr
6 hr
6 hr
6 hr
6 hr
Effects or Comments
Severe irritation, dyspnea,
and clouding of the cornea
Fatal in some cases
Fatal in some cases
Corrosion of the cornea and
upper respiratory irritation
Corrosion of the cornea and
upper respiratory irritation
Only slight corrosion of the
cornea and upper respiratory
irritation
Only slight corrosion of the
cornea and upper respiratory
irritation
Reference
45,64
45,69
45,69
45,64
45,64
45,64
45,64
(continued )
Ul
-J
-------
APPENDIX
TABLE 4 (Continued)
SUMMARY OF REPORTED EFFECTS OF INHALATION OF HYDROGEN CHLORIDE ON ANIMALS
Species
Rabbits
Guinea pigs
Pigeons
Monkey
Rabbit
Guinea pig
Concentra-
tion (ppm)*
100
100
100
33
33
33
Exposure
Time
6 hr/day for
50 days
6 hr/day for
50 days
6 hr/day for
50 days
6 hr/day
5 days/week
for 4 weeks
6 hr/day
5 days/week
for 4 weeks
6/hr/day
5 days/week
for 4 weeks
Effects or Comments
Slight unrest and irritation of
the eyes and nose
Slight unrest and irritation of
the eyes and nose
Slight unrest and irritation of
the eyes and nose
No immediate toxic effects and
no pathological changes
No immediate toxic effects and
no pathological changes
No immediate toxic effects and
no pathological changes
Reference
45,82
45,82
45,82
69
69
69
(continued)
Ul
oo
-------
APPENDIX
TABLE 4 (Continued)
SUMMARY OF REPORTED EFFECTS OF INHALATION OF HYDROGEN CHLORIDE ON ANIMALS
Species
Rabbits
Rabbits
Concentra-
tion (ppm)*
60
30
Exposure
Time
5 min
10 min
Effects or Comments
Cessation of ciliary activity
without recovery
Cessation of ciliary activity
without recovery
Reference
21
21
*1 ppm « 1,470 |-tg/m3 at 25°C.
ui
-------
APPENDIX
TABLE 5
SUMMARY OF REPORTED TOXIC EFFECTS OF HYDROGEN CHLORIDE EXPOSURE ON PLANTS
Species
Plants
Plants
Sugar beets
Viburnum
seedlings
Beech
Oak
Maple
Birch
Pear
Concentra-
tion (ppm)*
10-50
100-1,000
10
5-20
1,000
1,000
2,000
2,000
2,000
Exposure
Time
Few hr
24 hr
1 hr
1 hr
Effects or Comments
No leaf damage
Leaf damage
Threshold for marking
Leaves rolled at the edges,
withered, shrunk, faded, and
necrotic
Local lesions produced
Local lesions produced
Marginal leaf scorch
Marginal leaf scorch
Marginal leaf scorch
Reference
113
113
107
42
42
42
42
42
42
(continued)
-------
APPENDIX
TABLE 5 (Continued)
SUMMARY OF REPORTED TOXIC EFFECTS OF HYDROGEN CHLORIDE EXPOSURE ON PLANTS
Species
Viburnum
seedlings
Larch
Fir
Spruce
Tomato plants
Liriodendron
tulipifera
Alnus
fl,lutinosa
Prunus
serotina
Concentra-
tion (ppm)*
5-20
5-20
1,000
2,000
5
3
6
6
Exposure
Time
48 hr
48 hr
1 hr
1 hr/day for
80 days
2 hr
4 hr
4 hr
4 hr
Effects or Comments
Plants died
Plants died
Local lesions formed
No apparent injury
Developed interveinal bronzing
followed by necrosis within 72
hours after exposure
Threshold for visible injury
Threshold for visible injury
Threshold for visible injury
Reference
42
42
42
42
93
74
74
74
(continued)
-------
APPENDIX
TABLE 5 (Continued)
SUMMARY OF REPORTED TOXIC EFFECTS OF HYDROGEN CHLORIDE EXPOSURE ON PLANTS
Species
Acer saccharus
Acer
platanoides
Quercus rubus
Pinus strobus
Psaudotsuqa
mantissii
Abies
balsamea
Pinus abies
Pinus niqra
Concentra-
tion (ppm)*
7
7
13
8
10
10
19
18
Exposure
Time
4 hr
4 hr
4 hr
4 hr
4 hr
4 hr
4 hr
4 hr
Effects or Comments
Threshold for visible injury
Threshold for visible injury
No visible injury
Threshold for visible injury
Threshold for visible injury
Threshold for visible damage
Threshold for visible damage
No visible damage
Reference
74
74
74
74
74
74
74
74
(continued)
tsj
-------
APPENDIX
.TABLE 5 (Continued)
SUMMARY OF REPORTED TOXIC EFFECTS OF HYDROGEN CHLORIDE EXPOSURE ON PLANTS
Species
Thuja occi-
dentalis
Spruce
seedlings
Concentra-
tion (ppm)*
43
<50
Exposure
Time
4 hr
20 min
Effects or Comments
No visible damage
Plants died
Reference
74
61
*1 ppm = 1,470 |ag/m3 at 25°C.
U)
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APPENDIX
TABLE 6
EMISSIONS OF HYDROCHLORIC ACID IN SELECTED AREAS
OF NIAGARA COUNTY, N.Y.3
HC1 Emitted
Community (tons/year)
Cities:
Lockport 187
Niagara Falls 3,436
North Tonawanda 149
Towns:
Cambria 5
Hartland 5
Lewiston 191
Lockport 9
Newfane 16
Niagara 11
Pendleton 4
Porter 10
Royalton 7
Somerset 3
Wheatfield 24
Wilson 6
Villages:
Barker 3
Lewiston 3
Middleport 8
Wilson 3
Youngstown 3
Total 4,083
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APPENDIX
TABLE 7
HYDROCHLORIC ACID PRODUCTION IN THE UNITED STATES, 1958-196723
Hydrochloric
Acid*
Total HC1
Year (short tons)
1958
1959
1960
1961
1962
1963
1964
1965
1966
1967
826,
955,
970,
910,
1,052,
1,053,
1,236,
1,370,
1,519,
1,597,
022
914
167
967
116
502
824
092
372
682
i
i (short
107,
100,
90,
87,
105,
128,
136,
138,
139,
(preliminary) 137,
Process
Salt- Ac id
tons) (percent)
036
008
461
073
830
652
051
121
778
515
13.0
10.4
9.3
9.5
10.1
12.2
10.0
10.1
9.2
8.6
Synthesis
(short tons) (percent)
162,
165,
148,
118,
92,
92,
95,
99,
108,
114,
282
751
304
059
117
276
606
043
028
003
19.6
17.3
15.3
13.0
8.8
8.8
7.7
7.2
7.1
7.1
By-Product
and Others
(short tons) (percent )
556,
690,
731,
705,
854,
832,
1,005,
1,132,
1,271,
1,346,
704
155
402
835
169
574
167
928
566
164
67.4
72.3
75.4
77.5
81.8
79.0
82.3
82.7
83.7
84.3
* Includes anhydrous hydrogen chloride.
en
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66
APPENDIX
TABLE 8
PRODUCTION OF HYDROCHLORIC ACID BY PROCESS AND STATE88
State
Massachusetts
New Hampshire
New Jersey
New York
Pennsylvania
Alabama
Delaware
Georgia
Kentucky
Louisiana
Maryland
Tennessee
Texas
Virginia
West Virginia
Illinois
Indiana
Kansas
Michigan
Missouri
Ohio
California
Nevada
New Mexico
Washington
Total
Number
Salt-
Acid
1
3
1
1
2
1
1
1
1
2
1
15
of Plants
Direct
Synthesis
1
3
1
3
2
3
1
1
2
1
2
2
22
Using Each
By-
Product
1
7
5
1
2
2
3
3
1
1
8
6
2
2
6
1
4
3
1
1
60
Process
Total
2
1
10
6*
1
2
1
3
5*
5*
1
1
11*
2
6
3
3
1
7*
1
6*
5
1
1
3
88*
*Some plants use more than one process,
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67
APPENDIX
TABLE 9
MAJOR PRODUCERS OF HYDROCHLORIC ACID (MURIATIC ACID)
IN THE UNITED STATES
108
Company
Location
Allen, L. B., Co., Inc.
Allied Chemical Corp.,
Industrial Chemicals Div.
American Cyanamid Co.,
Industrial Chemicals Div.
American Oil & Supply Co.
Baker, J. T., Chemical Co.
Bay Chemical Co.
Berg Chemical Co., Inc.
Big Ben Chemicals & Solvents, Inc,
Calcine Chemical Co.
Celanese Corp. of America,
Chemical Div.
Central Chemical Div.
Diamond Alkali Co.
Dover Chemical Corp.
Dow Chemical Co.
Dowell Div.
Essex Chemical Corp.
General Aniline & Film Corp.
Globe Chemical Co., Inc.
Haviland Products Co.
Hooker Chemical Corp.
Industrial Chemicals Div.
Hubbard-Hall Chemical Co.
International Minerals &
Chemical Corp.
International Minerals &
Chemical Corp.
Johnson Mfg. Co.
Jones Chemicals, Inc.
Knight, Maurice A., Co.
Kraft Chemical Co.
McKesson & Robbins, Inc.,
Chemical Dept.
Mercury Chemical Corp.
Monarch Chemical Works, Inc.
Monsanto Inorganic Chemicals Div.
National Zinc Co., Inc.
Neville Chemical Co.
Nitine Inc.
Octagon Process Inc.
Schiller Park, 111.
Morristown, N.J.
Wayne, N.J.
Newark, N.J.
North Phillipsburg, N.J.
Chicago, 111.
New York, N.Y.
Chicago, 111.
Jersey City, N.J.
New York, N.Y.
Calumet City, 111.
Cleveland, Ohio
Dover, Ohio
Midland, Mich.
Tulsa, Okla.
Clifton, N.J.
New York, N.Y.
Cincinnati, Ohio
Grand Rapids, Mich.
Niagara Falls, N.Y.
Waterbury, Conn.
Skokie, 111.
Chicago, 111.
Princeton, Iowa
Caledonia, N.Y.
Akron, Ohio
Chicago, 111.
New York, N.Y.
Metuchen, N.J.
Omaha, Nebr.
St. Louis, Mo.
New York, N.Y.
Pittsburgh, Pa.
Whippany, N.J.
Edgewater, N.J.
(continued)
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68
APPENDIX
TABLE 9 (Continued)
MAJOR PRODUCERS OF HYDROCHLORIC ACID (MURIATIC ACID)
IN THE UNITED STATES108
Company
Location
Olin Mathieson Chemical Corp.
Pennsalt Chemical Corp.
Phillipp Brothers Chemicals Inc.
Potash Co. of America
PPG Industries Chemical Div.
Riverside Chemical Co., Inc.
Robinson Bros. Chemicals Inc.
Rohm & Haas Co.
Seaway Chemical Corp.
Siegel Chemical Co., Inc.
Solvent Chemical Co.
Smith-Douglass Co., Inc.
Stauffer Chemical Co.
Industrial Chemical Div.
Tenneco Chemicals Inc.
Triple-X Chemical Laboratories,
Inc.
United States Rubber Co.,
Chemical Div.
Velsicol Chemical Corp.,
Tennsyn Div.
Vulcan Materials Co.,
Chemicals Div.
Wittichen Chemical Co.
New York, N.Y.
Tulsa, Okla.
New York, N.Y.
Carlsbad, N. Mex.
Pittsburgh, Pa.
North Tonawanda, N.Y,
Brooklyn, N.Y.
Philadelphia, Pa.
Buffalo, N.Y.
Brooklyn, N.Y.
Maiden, Mass.
Norfolk, Va.
New York, N.Y.
New York, N.Y.
Chicago, 111.
Naugatuck, Conn.
Chattanooga, Tenn.
Wichita, Kans.
Birmingham, Ala.
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69
APPENDIX
TABLE 10
CONSUMPTION OF HYDROCHLORIC ACID BY USES, 196358
Uses Approximate %
Organic chemicals
Inorganic chemicals
Metal production
Metal and industrial cleaning
Food processing
Oil well acidizing
Total
49
5
17
7
4
18
100
100% HC1
(Short Tons)*
516,500
52,600
179,000
73,700
42,200
189,500
1,053,500
*Approximately calculated on basis of 1963 total pro-
duction of 1,053,502 short tons (see Table 7, Appendix).
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70
APPENDIX
TABLE 11
CONSUMPTION OF HYDROCHLORIC ACID BY
SELECTED INDUSTRIES, 1963 and 1958
Industry
Organic chemicals3
Intermediate coal tar products
Inorganic chemicals9-'*3
Alkalies and chlorine
Plastics material and resins
Total
100% HC1
1963
438,746
79,505
51,200
44,557
13,993
628,001
(Short Tons)
1958
280,822
18,802
24,400
12,280
36,754
373,058
aNot elsewhere classified.
^Estimated from total money spent in 1958 and 1963 by
inorganic chemical industries and prices paid during those
periods by other industries.
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APPENDIX 71
TABLE 12
CHLORINE CONTENT OF SELECTED UNITED STATES COALS95
Source of
State
Ohio
Illinois
Indiana
West Virginia
Pennsylvania
Illinois
Oklahoma
Coal
Bed
Sharon
No. 6
No. 4
Pittsburgh
Lower Freeport
Central Illinois
Henryetta
Chlorine Content
(percent)
0.01
0.01
0.06
0.07
0.14
0.35
0.46
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