PRELIMINARY
AIR POLLUTION SURVEY
OF
HYDROCHLORIC ACID
A LITERATURE REVIEW
. DEPARTMENT OF HEALTH, EDUCATION. AND WELFARE
Public Health Service
Consumer Protection and Environmental Health Service
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PREFACE
This document represents a preliminary literature review which is being used as a basis for
further evaluation, both internally by the National Ah* Pollution Control Administration
(NAPCA) and by contractors. This document further delineates present knowledge of the
subject pollutant, excluding any specific conclusions based on this knowledge.
This series of reports was made available through a NAPCA contractual agreement with
Litton Industries. Preliminary surveys include all material reported by Litton Industries as
a result of the subject literature review. Except for section 7 (Summary and Conclusions),
which is undergoing further evaluation, the survey contains all information as reported by
Litton Industries. The complete survey, including section 7 (Summary and Conclusions)
is available from:
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PRELIMINARY
AIR POLLUTION SURVEY
OF
HYDROCHLORIC ACID
A LITERATURE REVIEW
Quade R. Stahl, Ph.D.
Litton Systems, Incorporated
Environmental Systems Division
Prepared under Contract No. PH 22-68-25
U.S. DEPARTMENT OF HEALTH, EDUCATION, AND WELFARE
Public Health Service
Consumer Protection and Environmental Health Service
National Air Pollution Control Administration
Raleigh, North Carolina
October 1969
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The APTD series of reports is issued by the National Air Pollution Control
Administration to report technical data of interest to a limited reader-
ship. Copies of APTD reports may be obtained upon request, as supplies
permit, from the Office of Technical Information and Publications, National
Air Pollution Control Administration, U.S. Department of F(ealth, Education,
and Welfare, 1033 Wade Avenue, Raleigh, North Carolina 27605.
National Air Pollution Control Administration Publication No. APTD 69-36
11
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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)
Aldehydes (includes acrolein
and formaldehyde)
Ammonia
Arsenic and Its Compounds
Asbestos
Barium and Its Compounds
Beryllium and Its Compounds
Biological Aerosols
(microorganisms)
Boron and Its Compounds
Cadmium and Its Compounds
Chlorine Gas
Chromium and Its Compounds
(includes chromic acid)
Ethylene
Hydrochloric Acid
Hydrogen Sulfide
Iron and Its Compounds
Manganese and Its Compounds
Mercury and Its Compounds
Nickel and Its Compounds
Odorous Compounds
Organic Carcinogens
Pesticides
Phosphorus and Its Compounds
Radioactive Sub stances
Selenium and Its Compounds
Vanadium and Its Compounds
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
111
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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 epidemio-
logic studies were available.
Initially these reports were generally intended as
internal documents within NAPCA to provide a basis for sound
decision—mak± ig n 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 Fjnkelstein, Ph.D.
Douglas A. Olsen, PhOD.
James L. Haynes
i.v
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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.
V
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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 readily 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
vii
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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.
v i 11
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LIST OF TIBLES
1. “Ethyl’s Antiknock Compound—Tel Motor 33 Mix . . . . 27
2. Properties of Hydrogen Chloride and Hydrochloric
2 .cid 50
3. Summary of Reported Effects of Inhalation of Hydrogen
Chloride by Humans 52
4. Summary of Reported Effects of Inhalation of Hydrogen
ChiorideonAnimals 54
5. Summary of Reported Toxic Effects of Hydrogen
Chloride Exposure on Plants . . . . . . . 58
6. Emissions of Hydrochloric Acid in Selected Areas of
Niagara County, New York 62
7. Hydrochloric Acid Production in the United States,
1958—1967 ..... 63
8. Production of Hydrochloric Acid by Process and
State 64
9. Major Producers of Hydrochloric Acid (Muriatic Acid)
in the United States 65
10. Consumption of Hydrochloric Acid by Uses, 1963 . . . 67
11. Consumption of Hydrochloric Acid by Selected
Industries, 1963 and 1958 • 68
12. Chlorine Content of Selected United States Coals . . 69
ix
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FOR EWORD
ABSTRACT
CONTENT S
• . . • S
• S S •
An ima I s
1
3
.5. 3
5.. 3
.5 5
.. 5
.. 5
.. 6
.. 6
5. 7
.5 7
• . 10
• 5 11
• . 12
Sour ce S
Coal .
Fuel Oil .
Automobile Exhaust
Burning of Chloride—Containing
Plastics
3.4.5 Burning of Paper Products
3.4.6 DDT Production
3.4.7 Lemon Pulp Extraction . .
3.5 Environmental Air Concentrations
4 . A BAT E2 ’1ENT .
5 . EOJNOI4ICS • 34
1. INTRODUCTION
2 EFFECT S •
2.1 Effects on Humans
2.1.1 Toxicity . . . .
2.1.2 Sensory Thresholds
2.1.3 Synergistic Effects
2.2 Effects on Animals .
2.2.1 Commercial and Domestic
2.2.2 Animal Experiments .
2.3 Effects on Plants .
2.3.1 Phytotoxicity
2.3.2 Incidents of Plant Damage
2.4 Effects on Materials
2.5 Environmental Air Standards
S •
S 5
• S • S
3 . SOURCE S . • . . 1 4
• . S S S
• S • • S
• S • S S
3.1 Natural Occurrence
3.2 Production Sources . .
3.2.1 By—Product Process •
3.2.2 Salt—Acid Process
3.2.3 Chlorine—Hydrogen synthesis
3.3 Product Sources
3.3.1 Manufacture of Chemicals
3.3.2 Metal Production
3.3.3 OtherUses
3.4 Other
3.4.1
3.4.2
3.4.3
3.4.4
• 15
15
• 16
18
20
• • . • 21
21
• . . . 22
23
• . . . 23
• . • • 24
• . . . 26
• . . . 26
• S S
• 5 4
• • S
• 27
• 28
29
• 29
• 30
. • 31
xi
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CONTENTS (Continued)
6. ME PHODS OF ANALYS IS 35
6.1 Sampling Methods 35
6.2 Qualitative Methods 35
6.3 Quantitative Methods 36
REFERENCES . . . . . . . 39
A_PPEND]JC . . . . 49
xli
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1
1. INTRODUCTION
Hydrogen chloride (HCl) 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 arid attacks the
membranes of the eyes and upper respiratory tract. 34 ’ 73 The
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 i.g/m 3 (5 ppm*).] l 3 Irritation
of mucous membranes occurs at 15,000 .ig/m 3 (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
LLg/m 3 (10 to 50 ppm), 45 ’ 72 and irritation of the throat mem-
branes has been reported at exposures of 50,000 ug/m 3 (35 ppm). 87
Work becomes impossible at levels above 75,000 ug/m , 72 and
exposure to levels of 75,000 to 150,000 .iq/m 3 (50 to 100 p n)
cannot be tolerated by humans for longer than 60 minutes. 44 s 45 i 52 v 87
*Conversjon factor used. in this report: 1 ppm is approxi-
mately equal to 1,470 ug/m 3 .
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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 hydrochloric acid. are not as dangerous to humans
as hydrogen chloride gas because the acid has no strong dehy-
drating effect on the tissues. 87 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 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 diameter), whereas the workers exhibited no
change.
Prolonged exposure to low concentrations of hydrochloric
acid causes erosion of the teeth. 45 However, there are no known
systemic effects, either acute or chronic, from inhalation of
hydrochloric acid or hydrogen chloride. 49 ’ 87
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 xg/m 3 (0.067 to
0.134 ppm), 28,29 1,500 to 7,500 p.g/m 3 (1 to 5 ppm), 45 and 14,700
ig/m 3 (10 ppm). 105
Elf imova 28 ’ 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
Stayzhkin 85 ’ 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 Cl 2 + Concentration HC1
Odor threshold Cl 2 Odor threshold HCI
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 al. 69 exposed one monkey, three rabbits, and
three guinea pigs to 50,000 ug/m 3 (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
g/m 3 (33 ppm) may be dangerous. Rabbits and guinea pigs were
not killed at a concentration of 100,000 ug/m 3 (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 ig/m 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/m 3 (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. 45 ’ 69 Production of lesions in the liver and
other organs by hydrogen chloride is also described. 69
After Lehmann 64 exposed cats, rabbits, and guinea pigs
to 150,000 to 210,000 Mg/rn 3 (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/m 3 (1,350 ppm) for approximately 90 minutes. After approxi-
mately the same exposure time to a concentration of 5,000,000
Mg/rn 3 (3,400 ppm), death occurred in 2 to 6 days.
Leitz 65 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
Haseihoff and Lindau 42 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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that approximately 7,500 to 30,000 ig/m 3 (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 ig/m 3 (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 g/m 3 (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 ug/m 3 (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/m 3 (2,000 ppm) hydrogen chloride for 80 days. However,
recent studies by Lacasse 61 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 mdi—
cated by a marginal leaf burn that progresses basipetally with
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prolonged exposure. 42 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 ig/m 3 (50 to 100 ppm) hydrogen chloride,
but these values were obtained with no air circulation over
the plants. Thomas 107 found that the marking threshold for
sugar beets was a few hours’ exposure at 15,000 ig/m 3 (10 ppm).
Lacasse et al. 62 ’ 74 ’ 93 have recently studied the effects
of low concentrations of hydrogen chloride on plants. Tomato
plants were exposed to 7,500 ig/m 3 (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 i0 4 ergs/cm 2 —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 The experimental conditions were as follows:
exposure to 4,500 to 64,500 i ig/m 3 (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 lO 4 ergs/cm 2 —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 iriterveinal necrosis and necrotic flecking.
The only sylrntom observed for the coniferous species was tip
necrosis. , riod of time for the first appearance of injury
varied betweon 8 and 24 hours.
Lacasse 62 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 107 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) 04
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 46 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 .ig/m 3 (119 to 473 ppm) hydrochloric acid
and 1,560 to 2,760 ig/m 3 (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. 107 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 j.g/m 3 (30 ppm) of hydrogen chloride
remained in the stack effluent. This control eliminated the
plant damage.
Bohne 13 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. 4975
Mellor 75 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 IndustrialHygien—
ists (ACGIH) has adopted 7,000 j ig/m 3 (5 ppm) as the threshold
concentration for hydrogen chloride for an 8—hour day, 5—day
week. 11 ’
West Germany has also established 5 ppm as the permis-
sible work—station concentration. 55 West Germany has also
established an ambient air quality standard of 0.5 ppm (approxi-
mately 700 .ig/m 3 ) of hydrogen chloride for a 30—minute mean
average, with a maximum of 1.0 ppm (1,400 ug/m 3 ) of hydrogen
chloride for a 30—minute mean average. 55
Russia has established 15 ug/m 3 (0.009 ppm) as a 24—
hour maximum average for ambient air concentration of hydrogen
chloride and a maximum of 50 ig/m 3 of hydrogen chloride (0.03
ppm) for a single exposure. 55 ’ 73 The standard for a 24-hour
average is below the concentrations which might cause reflexive
reaction of the sensory organs. 86
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 3 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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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 Of 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 ’ -° 6 (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 ’ 1 - 06
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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 tetrachioride 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 tetrachioride or chlorobenzene, or may be used to pre-
pare an intermediate for a non—chioro—containing end product,
as in the preparation of phenol from benzene using chlorobenzene
(Equations 2 and 3).
CH 4 + 4C1 2 — )CC1 4 + 4HC1 (Equation 1)
(Methane) (Carbon tetrachioride)
C H 6 + Cl 2 — ) C 8 H 5 C1 + HC1 (Equation 2)
(Benzene) (Chlorobenzene)
C 5 H 5 C1 + NaOH ) C 5 H 5 OH + NaC1 (Equation 3)
(Chlorobenzene) (Phenol)
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
nonchiorinated 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. 6 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 ,€ 3 l 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, NaC1)
is reacted with sulfuric acid (600 or 66° Bauine). 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
juations 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.
NaC1 + H 2 S0 4 )NaHSO 4 + HC1 ( uation 4)
NaHSO 4 + NaC1 ) Na 2 SO 4 + HC1 (Djuation 5)
Generally, the salt and a slight excess of acid are
heated to 1,400 to l,600 0 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 0 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 Haryreaves process. 58 ’ 92 In 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 0 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.
4NaC1 + 2S0 2 + 02 + 21120 >2Na 2 SO 4 + 4HC1 (Equation 6)
Hydrogen chloride emissions from the salt—acid process
are higher than those from either of the other two processes. 7
In the Mannheirn 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. 91 ’ 92 In the 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 e thaust 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. 5 ° 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.
nissions 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 ’ 1 -° 6 The resulting product is
98 to 99,7 percent pure)-° 6 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. 7
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 0
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21
3.3 Product Sources
Hydrochloric acid and hydrogen chloride have a wide
variety of uses; 58 ’ 76 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 (oxyhydrochiorination) to prepare
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22
polychiorinated 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 chioroprene
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 disaussed 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 salts 27 that are solu-
ble in water. 22 When coal burns, most of the chloride salts
are converted to hydrogen chloride, 57 ’ 58 which is then emitted
into the athxsphere.
Analysis of United States coals shows that the chlorine
content ranges from 0.01 to 0.56 percent.1i 5 l 7 B.B 9 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 Vliet 8 ° 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 Bienstoc]c 51 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 0 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 1975.11 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 1967.23 lapalucci, Demski, and Bienstock 51 - 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 94 cited two 1938 reports on chloride emissions.
In one repcrt 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” 7 indicated that the
maximum hydrogen chloride content in emissions was approxi—
inately 46 p *n 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. 3 ° 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 (TI4L), 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 MIX 101
Weight
Compound (percent)
Tetraethyl lead 57.5
Methyl cyclopentad ieny—
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 83
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 ’ 8 ’ Studies have been conducted with poly-
vinyl chloride films 1 - 2 ’ -to determine the type and quantity
of gases evolved. In one investigation,’ 2 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 lOO 0 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
g/m 3 ; after 2 hours, 12,000 p g/m 3 ; and after 3 hours, 20,000
ig/m 3 .
Th y - , open burning or incineration of chlorinated plas-
tics is probable source of hydrochloric acid pollution.
Without tfective 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, 1 - 0 i 3 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 (dichiorodiphenyltrichioroethane) is a common pesti-
cide manufactured from chioral, chlorobenzene, and sulfuric
acid 2 (see Equation 7).
H SO 4
CC1 3 CHO + 2C 8 H 5 C1 ) CC1 3 cH(C 5 H 4 C1) 2 + H 2 0
(Chioral) (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 chioral. 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 reactiox .
3.4.7 Lemon Pulp Extraction
One company has reported on the extraction of lemon pulp
with isopropyl alcohol at l200F. 8 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, Gorhaxn 4 ° observed
that in Great Britain, precipitation samples from urban areas
exhibited r 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. 50 ’ 58 r 1 - 06 The packed
tower systems 50 .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. 58 The most common system is the co—current falling film
absorbers. 49 ’ 58 ’ 59 In 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. 5 0
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 a l., 3 ’ 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. -° 6
Other systems that appear to be effective for the con-
trol of hydrochloric acid or hydrogen chloride emissions are
the rotary brush scrubber 59 and the ejector venturi scrubber. 4 ’
With the former system, collection efficiencies of 99.995 per-
cent have been reported with an initial hydrogen chloride
content of 610 g/m 3 . In the latter system, scrubbing eff i-
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 c 7 l Adsorbents investigated
include chromium oxinate 9 and basic salts 36 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 5 - 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 resented 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 eff i—
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
be 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 ihich have been collected in water may be determined
quantitatively by the usual direct titration methods with
standard bases. 25
A spectrophotometric method for determination of strong
acids has been reported. 39 ’ 7 ° After the air sample is passed
through water, methyl red is added to the acidic solution and
the optical density at 530 m -L is determined. Normal concen-
trations of carbon dioxide and 1,000 .ig of sulfur dioxide per
m 3 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 and 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
In the absence of soluble chloride salts, hydrochloric
acid samples dissolve in water and may be determined by the
standard methods for chloride determination, 99 including the
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37
Mohr method, 99 ’ - 00 absorption indicator method, 32 ’ 6 ° and
the modified Voihard method. 15 These methods have a sensi-
tivity of approximately 18,000 ig of chloride per liter.
For very small amounts of chloride in air, the determination
can be made turbidimetrically or nephelometrically. 24 1 79 1 99
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 colorimetrica11y. 5 ’ 116
This method is based on the yellow color produced by the iron(III)
chioro complex in perchioric acid with a sensitivity of
approximately 1,000 ig/xn 3 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
An automated analysis method for chloride is used by
the National Air Sampling Network. - - 0 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 rn i. The relative
standard deviation for chloride is 1.0 ± 0.1 ig/ml .
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. 4 ’ 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
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Albany, N.Y. (1964).
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Biology (Bethesda, Nd.: Federation of American Societies
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Administration and Manufacturing Chem’ Association,
Inc. (To be published).
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12. Boettner, E. A., and B. Weiss, An Analytical System for
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Am. Ind.j yq. Assoc. J . 28:535 (1967).
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40
14. Bureau of the Census, U. S. Department of Commerce,
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md. &ig. Chem . 7:38 (1935).
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17. Chaigneau, N., and M. Santarromana, Dosage de l’acide
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reactifs solides, Mikrochim. Acta 1965:976 (1965).
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of Chlorinated Plastics, J. Appl. Chern . 4:379 (1954).
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-------
APPENDIX
-------
APPENDIX
TABLE 2
PROPERTIES OF HYDROGEN CHLORIDE AND HYDROCHLORIC ACID 49 ’ 76
Properties
Hydrogen Chloride
(HC1)a
Hydrochloric Acid
(HC1, agua)b
Color, odor, normal
state
Colorless gas 1 pungent,
irritating odor, fumes
in air
Colorless liquid; sometimes yellowish
due to impurities (iron, arsenic,
chlorine, and organic matter); pungeni
and irritating odor
Boiling point
—85°C (—121°F)
Aqueous solution containing 20.24%
HC1: 110°C (230°F)
Melting point
—111°C (—168°F)
27.92% HC1: —42°C (—43.6°F)
37.14% HC1: —74°C (—101.2°F)
Hygroscopicity
Very hygroscopic
Hygroscopic
Density
1.6397 g/l (0°C, 760 mm
20.04% FIC1: 1.1006 g/l
37.14% HC1: 1.1885 g/l
Heat of fusion
476-504.5 g—cal/mole
Heat of vaporizatior
3860±4 g—cal/mole
(continued)
-------
TABLE 2 (Continued)
PROPERTIES OF HYDROGEN CHLORIDE AND HYDROCHLORIC ACID 49 ’ 76
Properties
Hydrogen Chloride
(HC1)a
Hydrochloric Acid
(HC1, agua)b
Reactivity
Non—corrosive when dry.
Reacts rapidly with man
organic materials
Highly corrosive to moist metals with
evolution of hydrogen gas. Reacts
with basic salts (metallic oxides and
carbonates)
Solubility in H 2 0)
(g/lOOg 1120)
82.3 ( 0°c)
67.3 (30°C)
63.3 (40°C)
59.6 (50°C)
56.1 (60°c)
aA1SO called hydrochloric acid, anhydrous.
bAlso called muriatic acid.
U,
-J
-------
APPENDIX
TABLE 3
SUMMARY OF REPORTED EFFECTS OF INHALATION OF HYDROGEN CHLORIDE BY HUMANS
Concentratior
— (ppm)*
Exposure
Time
— Effects or Comments —
Reference
50—100
Work is impossible
45,72
10—50
Work is difficult but possible
45,72
10
Work is undisturbed
45,72
1,300-2,000
Few mm
Lethal
52,103
1,000—1,300
30—60 mm
Dangerous
52
50—100
60 mm
Intolerable
35,44,52,87
35
Irritation of throat after short exposure
87
1,000—2,000
Brief exposures are dangerous
87
10
Irritation
113
5
No organic damage
113
0,
N .)
(continued)
-------
APPENDIX
TABLE 3 (Continued)
SUMMARY OF REPORTED EFFECTS OF INHALATION OF HYDROGEN CHLORIDE BY HUMANS
Concentration
— (ppm)*
Exposure
Time
Effects or Comments
Reference
10
Odor threshold value
105
0.067—0.134
Odor threshold value
28,29
0.402
Concentration for threshold reflex effect
on optical chronaxie
28,29
0.134
Concentration for threshold reflex effect
on eye sensitivity to light
28,29
0.335
Concentration for threshold effect on
digito—vascular toxicity
28,29
0.067—0.134
Threshold concentrations of change in the
rhythm and depth of respiratory movement
28,29
1—5
Odor threshold value
45
*1 ppm = 1,470 .ig/m 3
at 25°C.
U,
-------
APPENDIX
TABLE 4
SUMMARY OF REPORTED EFFECTS OF INHALATION OF HYDROGEN CHLORIDE ON ANIMALS
Species
Concentra—
tion (ppml*
Exposure
Time
Effects or Comments
Reference
Rabbits
4,300
30 mm
Fatal in some cases, due to
laryngeal spasm, laryngeal
edema, or rapidly developing
pulmonary edema
45,69
Guinea pigs
4,300
30 mm
Fatal in some cases, due to
laryngeal spasm, laryngeal
edema, or rapidly developing
pulmonary edema
45,69
Cats
3,400
90 mm
Death after 2 to 6 days
45,64
Rabbits
3,400
90 mm
Death after 2 to 6 days
45,64
Guinea pigs
3,400
90 mm
Death after 2 to 6 days
45,64
Cats
1,350
90 mm
Severe irritation, dyspnea,
and clouding of the cornea
45,64
Rabbits
1,350
90 mm
Severe irritation, dyspnea,
and clouding of the cornea
45,64
(continued
-------
APPENDIX
TABLE 4 (Continued)
SUMMARY OF REPORTED EFFECTS OF INHALATION OF HYDROGEN CHLORIDE ON ANIMALS
Species
Concentra—
tion (pprn)*
Exposure
Time
Effects or Comments
Reference
Guinea pigs
1,350
90 mm
Severe irritation, dyspnea,
and clouding of the cornea
45,64
Rabbits
670
2 hr
Fatal in some cases
45,69
Guinea pigs
670
2 hr
Fatal in some cases
45,69
Rabbits
300
6 hr
Corrosion of the cornea and
upper respiratory irritation
45,64
Guinea pigs
300
6 hr
Corrosion of the cornea and
upper respiratory irritation
45,64
Rabbits
100—140
6 hr
Only slight corrosion of the
cornea and upper respiratory
irritation
45,64
Guinea pigs
100—140
6 hr
Only slight corrosion of the
cornea and upper respiratory
irritation
45,64
continued
(7 1
a,
-------
APPENDI X
TABLE 4 (Continued)
SUMMARY OF REPORTED EFFECTS OF INHALT TION OF HYDROGEN CHLORIDE ON ANIMALS
Species
Concentra —
tion (ppm)*
Exposure
Time
Effects or Comments - -
Reference
Rabbits
100
6 hr/day fot
50 days
Slight unrest and irritation o
the eyes and nose
45,82
Guinea pigs
100
6 hr/day fo
50 days
Slight unrest and irritation of
the eyes and nose
45,82
Pigeons
100
6 hr/day foi
50 days
Slight unrest and irritation 0±
the eyes and nose
45,82
Monkey
33
6 hr/day
5 days/week
for 4 weeks
No immediate toxic effects and
no pathological changes
69
Rabbit
33
6 hr/day
5 days/week
for 4 weeks
No immediate toxic effects and
no pathological changes
69
Guinea pig
33
6/hr/day
5 days/week
for 4 weeks
No immediate toxic effects and
no pathological changes
69
(continued)
-------
APPENDIX
TABLE 4 (Continued)
SUMMARY OF REPORTED EFFECTS OF INHALATION OF HYDROGEN CHLORIDE ON ANIMALS
Species
Concentra—
tion (ppm)*
Exposure
Time
Effects or Comments
Reference
Rabbits
60
5 mm
Cessation of ciliary activity
without recovery
21
Rabbits
30
10 mm
Cessation of ciliary activity
without recovery
21
*1 ppm 1,470 g/m 3 at 25°C.
-------
APPENDIX
TABLE 5
SUMMARY OF REPORTED TO)CtC EFFECTS OF HYDROGEN CHLORIDE EXPOSURE ON PL? NTS
Species
Concentra—
tion (ppni)*
Exposure
Time
Effects or Comments
Reference
Plants
10—50
No leaf damage
113
Plants
100—1,000
Leaf damage
113
Sugar beets
10
Few hr
Threshold for marking
107
Viburnum
seedlings
5—20
24 hr
Leaves rolled at the edges,
withered, shrunk, faded, and
necrotic
42
Beech
1,000
1 hr
Local lesions produced
42
Oak
1,000
1 hr
Local lesions produced
42
Maple
2,000
Marginal leaf scorch
42
Birch
2,000
Marginal leaf scorch
42
Pear
2,000
Marginal leaf scorch
42
(continued)
-------
APPENDIX
TABLE 5 (Continued)
SUMMARY OF REPORTED TOXIC EFFECTS OF HYDROGEN CHLORIDE EXPOSURE ON PLANTS
U,
Species
Concentra-
tion (ppm)*
Exposure
Time
Effects or Comments
Reference
Viburnum
seedlings
5-20
48 hr
Plants died
42
Larch
5—20
48 hr
Plants died
42
Fir
1,000
1 hr
Local lesions formed
42
Spruce
2,000
1 hr/day for
80 days
No apparent injury
42
Tomato plants
5
2 hr
Developed interveinal bronzing
followed by necrosis within 72
hours after exposure
93
Liriodendron
3
4 hr
Threshold for visible injury
74
tulirDi fera
-F
AJ.nu 5
gJ.utino.sa
6
4 hr
Threshold for visible injury
74
Prurius
serotina
6
4 hr
Threshold for visible injury
74
(continued:
-------
APPENDIX
TABLE 5 (Continued)
SUMMARY OF REPORTED TOXL C EFFECTS OF HYDROGEN CHLORIDE E)G’OSURE ON PLANTS
Concentra—
(pprn)*
Expo sure
Time
Effects or Comments
Reference
Acer saccharus
7
4 hr
Threshold for visible injury
74
Acer
platanoides
7
4 hr
Threshold for visible injury
74
Quercus rubus
13
4 hr
No visible injury
74
Pinus strobus
8
4 hr
Threshold for visible injury
74
Psaudotsuga
mantissii
10
4 hr
Threshold for visible injury
74
Abies
balsamea
10
4 hr
Threshold for visible damage
74
Pinus abies
19
4 hr
Threshold for visible damage
74
Pinusnigra
18
4 hr
No visible damage
74
(continued)
-------
APPEND X
TABLE 5 (Continued)
STJI ’1NARY OF REPORTED TOXEC EFFECTS OF HYDROGEN CHLORIDE EXPOSURE ON PLANTS
Species_
Concentra—
— tion (ppm)*
Exposure
Time
Effects or Comments
Reference
muja occl—
dentalis
43
4 hr
No visible damage
74
Spruce
seedlings
<50
20 mm
Plants died
61
*1 ppm = 1,470 ig/m 3 at 25°C.
-J
-------
APPENDIX
TABLE 6
EMISSIONS OF HYDROCHLORIC ACID IN SELECTED AREAS
OF NIAGARA COUNTY, N..Y. 3
HC1 Emitted
Community (tons/yearj
Cities:
Lockport 187
Niagara Falls 3,436
North Tonawanda 149
Towns:
Cambria 5
Hartland 5
i.,ewiston 191
Loclcport 9
Newfane 16
Niagara 11
Pendleton 4
Porter 10
Royalton 7
Somerset 3
Wheatfielcl 24
Wilson 6
Villages:
Barker 3
Lewiston 3
Middleport 8
Wilson 3
Youngstown 3
Total 4,083
-------
AP ’ENDIX
TABLE 7
HYDROCHLORIC ACID PRODUCTION IN THE UNITED STATES, 1958_196723
Year
Hydrochloric
Acid*
Total HC1
(short tons)
Process
Salt—Acid
(short tons)(percent)
Synthesis
(short tons)(percent)
By—Product
and Others
(short tons)(percent
1958
826,022
107,036 13.0
162,282 19.6
556,704 67.4
1959
955,914
100,008 10.4
165,751 17.3
690,155 72.3
1960
970,167
90,461 9.3
148,304 15.3
731,402 75.4
1961
910,967
87,073 9.5
118,059 13.0
705,835 77.5
1962
1,052,116
105,830 10.1
92,117 8.8
854,169 81.8
1963
1,053,502
128,652 12.2
92,276 8.8
832,574 79.0
1964
1,236,824
136,051 10.0
95,606 7.7
1,005,167 82.3
1965
1,370,092
138,121 10.1
99,043 7.2
1,132,928 82.7
1966
1,519,372
139,778 9.2
108,028 7.1
1,271,566 83.7
1967
1,597,682
(preliminary) 137,515 8.6
114,003 7.1
1,346,164 84.3
*Includes anhydrous hydrogen chloride.
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APPENDIX
TABLE 8
PRODUCTION OF HYDROCHLORIC ACID BY PROCESS ? ND STATE 88
— Number
Salt—
of Plants
Direct
Using
Each
By—
Process
State Acid
Synthesis
Product
Total
Massachusetts 1 1 2
New Hampshire 1 1
New Jersey 3 7 10
New York 3 5 6*
Pennsylvania 1 1
Alabama 2 2
Delaware 1 1
Georgia 1 2 3
Kentucky 1 3 3 5*
Louisiana 2 2 3 5*
Maryland 1 1
Tennessee 1 1
Texas 1 3 8 11*
Virginia 1 1 2
West Virginia 6 6
Illinois 1 2 3
Indiana 1 2 3
Kansas 1 1
Michigan 2 6 7*
Missouri 1 1
Ohio 2 1 4 6*
California 2 3 5
Nevada 1 1
New Mexico 1 1
Washington 2 1 3
Total 15 22 60 88*
*Some plants use more than one process.
64
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65
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.
Calcjne 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, Ill.
Morristown, N.J.
Wayne, N.J.
Newark, N.J.
North Phillipsburg, N.J.
Chicago, Ill.
New York, N.Y.
Chicago, Ill.
Jersey City, N.J.
New York, N.Y.
Calumet City, Ill.
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, Ill.
Chicago, Ill.
Princeton, Iowa
Caledonia, N.Y.
Akron, Ohio
Chicago, Ill.
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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66
APPENDIX
TABLE 9 (Continued)
MAJOR PRODUCERS OF HYDROCHLORIC ACID (MURIATIC ACID)
IN THE UNITED STATES’° 8
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 Chemical s 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, Okia.
New York, NY.
Carlsbad, N. Mex.
Pittsburgh, Pa.
North Tonawanda, N.Y.
Brooklyn, N.Y.
Philadelphia, Pa.
Buffalo, N.Y.
Brooklyn, N.Y.
Malden, Mass.
Norfolk, Va.
New York, N,Y.
New York, N.Y.
Chicago, Ill.
Naugatuck, Conn.
Chattanooga, Tenn.
Wichita, Kans.
Birmingham, Ala.
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APPENDIX
TABLE 10
CONSUMPTION OF HYDROCHLORIC ACID BY USES,
196358
67
Uses
Organic chemicals
Inorganic chemicals
Metal production
Metal and industrial cleaning
Food processing
Oil well acidizing
Total
Approximate %
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
*Approxjmately calculated on basis of 1963 total pro-
duction of 1,053,502 short tons (see Table 7, Appendix).
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68
APPENDIX
TABLE 11
CONSUMPTION OF HYDROCHLORIC ACID BY
SELECTED INDUSTRIES, 1963 and 195814
Industry
Organic chemicalsa
Intermediate coal tar products
Inorganic chemicalsa ,b
Alkalies and chlorine
Plastics material and resins
Total
100% HC1 (Short Tons )
1963 1958
438,746 280,822
79,505 18,802
51,200 24,400
44,557 12,280
13,993 36,754
628,001 373,058
aNot elsewhere classified.
bEstimated 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 69
TABLE 12
CHLORINE CONTENT OF SELECTED UNITED STATES COALS 95
Source of Coal Chlorine Content
Bed - — (percent)
Ohio Sharon 0.01
Illinois No. 6 0.01
Indiana No. 4 0.06
West Virginia Pittsburgh 0.07
Pennsylvania Lower Freeport 0.14
Illinois Central Illinois 0.35
Oklahoma Henryetta 0.46
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