MORE ON PHOSGENE, METHYL ISOCYANATE
AND THE UNION CARBIDE…
AND THE UNION CARBIDE…
In the previous
article – “Killer Gas of Bhopal – Phosgene, not MIC” – we have conclusively
established that it could not be MIC ‘gas’ (which after all is a liquid
with b.p. around 40oC) which played havoc with the lives of the
people of Bhopal. We also concluded that it could be nothing but Phosgene which
was the real ‘criminal’. In this article, we try to substantiate our arguments
about the identity of the killer gas as Phosgene with more positive evidence
and also delve into some more details about Phosgene, MIC and their attendant
usual hazards.
Phosgene was the most
efficacious killer gas which was introduced first by Germans in the World War I
with sensational results and gruesome tragedies. Phosgene is a type of choking
gas. We have already learnt about its chemical name and formula (COCl2)
–
“The name, phosgene,
is derived from Greek meaning generated by light. It was first prepared by John
Davy in 1811 by exposing equal quantities of carbon monoxide and chlorine to
sunlight. It is used in industry in the manufacture of dyes and for various
other purposes. This gas, therefore, was not new when it was first used as a
chemical warfare agent by the Germans in a cloud gas attack on the British in
December, 1915… it is still an important combat chemical. Its symbol, CG,
derives from name given to phosgene by the French, Collongite.
Phosgene is very
effective in low concentrations. …it is extremely dangerous because when breathed
in low concentrations it may not be immediately severely irritating.
Frequently, unless a man has breathed a large amount, the effects may be
delayed for several hours or even a day. The symptoms of phosgene poisoning are
first coughing and choking. This is followed by inability to expand the chest,
hurried and shallow breathing, and sometimes vomiting. Next there is severe
pain in the chest, and finally there is blueness of the lips (cyanosis) with
either a red bloated face (venous conjection) or with face of grayish colour
indicating failing circulation.
Phosgene irritates the
nose and the throat only slightly and for this reason men are likely to
inhale it more deeply than they would similar concentrations of some other
irritating gas such as chlorine. Consequently, men gassed with CG
frequently have very little warning that they have been severely affected until
it is too late to avoid the danger.
The effect of the gas
is cumulative; exposure to even low concentrations over a long period of time may
cause severe casualties. A phosgene casualty is very similar to a case of
pneumonia and in fact the effect might be called a chemical pneumonia.
The insidious
nature of phosgene must be understood, since it is not unusual for a man to be
seriously gassed without knowing it until for late, and because the delayed
effect is frequently responsible for failure to provide for proper treatment.
It is the rule that a man suspected of having breathed phosgene should be
treated as a serious casualty until at least twenty four hours have passed. As
an example of the delayed action following breathing of a high concentration of
phosgene, the following extract from the British Official History of the War
(1914-1918) may be cited:-
February 3rd,
1917: A chemist was working on a new chemical product. A siphon of phosgene,
required for the synthesis of this substance, burst on his table at 1.00 p.m. A
yellowish cloud was seen by a second person in the room to go up close to the
chemist’s face, who exclaimed, “I am gassed,” and both hurried out of the room.
Outside, the patient sat down on a chair, working [looking?] pale and coughing
slightly.
2.30 p.m. In bed at
hospital, to which he had been taken in a car, having been kept at rest since
the accident. Hardly coughing at all; pulse normal. No distress or anxiety and
talking freely to friends for over an hour. During this time he was so well
that the medical officer was not even asked to see the patient upon admission
to the hospital.
5.30 p.m. Coughing,
with frothy expectoration, commenced and the patient was noticed to become
bluish about the lips. His condition now rapidly deteriorated. Every fit of
coughing brought up large quantities of clear, yellowish frothy fluid, of which
about 80 ounces were expectorated in one and a half hours. His face became of a
grey ashen colour, never purple though the pulse remained fairly strong. He
died at 6.50 p.m. without any great struggle for breath. The symptoms of
irritation were very slight at the
onset; there was then a delay of at least four hours, and the final development
of serious edema up to death took little more than an hour though the patient
was continually rested in bed.
Emphasis on the delayed effect of phosgene should not
lead one to believe that its action is normally slow when high concentrations
are breathed. Generally under
such conditions the effect is immediate and the man becomes a serious casualty
at once.
The odour of phosgene
is very characteristic. The usual description of the odor of phosgene compared
it to the odor of musty hay or of green corn. Some say it smells like newly
mown hay. There is also present the suggestion of acid; the individual may note
a sour taste in his moth if he breathes much of it.
Phosgene vapour is
more than three times heavier than air. A cloud of phosgene, unless it is
carried upward by the wind or air currents, will remain near the ground until
it is much diluted. This is a great advantage in warfare because the heavy gas
will flow into ravines, trenches and dugouts, places where men normally seek
refuge against bullets and explosives.
Because phosgene is a
gas, except in cold weather (below 47oF i.e. 8.2oC), it is non-persistent and
is dissipated rapidly by the wind. In winter weather it will have some what
greater persistence than in warm weather, but even at low temperature, it
evaporates rather rapidly.
Phosgene is a gas with which the soldier can take no
chances. Too much emphasis cannot be given to its insidious nature
and dangerous properties. If the odor of CG is detected there is only one thing
to do and that is to stop breathing until the gas mask has been carefully
adjusted. One good breath of the gas can cause a serious casualty. (See
‘Gas Warfare’ by Brig. General Alden H. Waitt, Revised edition 1944,
Duell, Sloan and Pearce, NEW YORK – pp. 39-43.)
Though the foregoing
description is quite detailed, educative and crystal-clear, we would like to
supplement it with extensive quotations from other sources too:
“TOXIC PROPERTIES: Phosgene
and Diphosgene rapidly react with the moist surfaces of the mucus membranes and
destroy the function and structure of the cells, causing immediate irritation.
Then follows the development of edema of the lungs which is formed in the
course of several hours during which the plasma of the blood permeates through
the destroyed walls of the bronchioli. This phase corresponds to the clinical
period of latency, which is more or less free from subjective complaints. When
the edema has reached a certain degree, it becomes suddenly clinically apparent
through impairment of the respiration. The breathing surface of the lungs is
reduced through the liquid in the bronchioli, lack of oxygen, suffocation
occurs. The victim is drowned from within and may now succumb. This process
develops within 24 hours, sometimes slower.
TOXIC CONCENTRATIONS
of both phosgene and diphosgene are of the same magnitude. The susceptibility
of man is also of the same magnitude as that of the commonly used laboratory
animals.
40 mg per m3 in a few seconds cause fighting inefficiency.
160 mg per m3 in 1 minute is highly toxic.
40 mg per m3 in 25 minutes may be fatal.
20 mg per m3
in 50 minutes may be fatal.
Smallest
concentrations affect the sensations of smell and taste.
Tobacco smoking after such exposure is felt as disagreeable.
Tobacco smoking after such exposure is felt as disagreeable.
Effect on men:
The initial period of irritation to the eyes and the throat is followed by a
period of latency lasting from 2 to 8 hours, in some cases for three days,
during which no or almost no complaints are felt. Then, the color of the face
becomes ash grey while there may still be not more than a slight feeling of
discomfort, the slightest effort of the patient, an attempt to change his
position in bed may produce sudden collapse or death. This state is called
the “grey stage asphyxia.” The tissues of the body are at minimum of oxygen
supply, at the same time no accumulation of Carbon Dioxide (CO2)
takes place, as in the case of ordinary asphyxia. First aid men and doctors
must know this condition. When such patients
were loaded into ambulances they arrived dead at the hospital.
In the further
development of the disease, Carbon-di-oxide is accumulated in the organs and
especially in the blood and produces the familiar picture of cyanosia and
dyspnoea which is now called “blue stage asphyxia.” At this time the edema of
the lungs is at its summit. The patient breathes rapidly and spasmodically, the
chest is tight and constricted, severe pains in the chest, highest degree of
asphyxia, blue red cyanosis, desperate restlessness, delirium, expectoration of
yellow-reddish liquid from the lungs, vomiting and desperate anxiety produce a
most impressive clinical picture. It is
hardly bearable even for the most cool-hearted physician to pass through a
hospital room, where many such patients lie and suffer.
The fate of the
patient depends upon the resistance which his circulatory system opposes to the
tremendous strain of internal asphyxia. Those who survive the first three days
may be considered saved.
Complications,
especially secondary infections, pneumonia at a late stage of the disease may
still develop. Chronic bronchitis, bronshiectasis, emphysema, “al veolite
vegetante” were observed in animal experiments and later in human cases.
Late sequelae may be
classified as being of the bronchitic asthmatic, circulatory, cachectic or
nervous type.
TREATMENT is
symptomatical, removal of the patient from further exposure to gas, elimination
of even the slightest strain, application of warm and fresh clean but not
cool air, inhalation of oxygen from the first beginning until the blue stage
asphyxia is overcome, an all be given by the first aid personnel or laymen,
before medical aid is available. Other measures are reserved to the physician:
phlebotomy, intra-venous infusions of salt or glucose solution, calcium preparations,
digitalis, strophenthus, caffeine, scilla maritime, ephetonin, quinine. The
physician knows that in phosgene poisoning, no use of morphine, lobeline and
other remedies should be made which affect the respiratory centre.
PROTECTION through gas
masks and respirators is satisfactory.” [See, ‘Chemical Warfare’ by Curt
Wachtel, Chapman & Hall Ltd., London ,
1941, pp. 156-158, emphases ours.]
Further –
“The importance of
Phosgene as an industrial hazard is its toxicity. It is over ten times as toxic
as Chlorine for a concentration of 0.50 mg per litre is lethal for an exposure
of 10 minutes.
Serious symptoms may
not develop until several hours after exposure for the immediate symptoms
produced by even a lethal dose may be relatively mild since phosgene elicits no
marked respiratory reflexes and thus a person who appears to be but
slightly gassed immediately following exposure may become a serious casualty
several hours later. Phosgene is a lung irritant and causes severe damage to
the alveoli of the lungs; this is followed by pulmonary edema, resulting in
asphyxiation. Inhalation of this gas produces catching of the breath, choking,
immediate coughing, tightness of the chest, slight lachrymation, difficulty
and pain in breathing and cyanosis. Its effects are probable due to
hydrolysis and he formation of hydrochloric acid (HCl) inside the body.
The most pronounced
symptoms of phosgene poisoning are coughing with bloody sputum
and weakness which may last for several months.
An atmosphere
containing 1 part by volume of the gas in 6000 may cause lung injuries in 2
minutes, 1 part in 30,000 is very dangerous and 1 part in 2,00,000 is probably
fatal for exposures of 30 minutes. The maximum permissible concentration for a
prolonged exposure period is about 0.1 ppm. – that is 0.004 mg per litre.
The least detectable
odor of phosgene is 5.6 parts per million, the least concentration that affects
the throat is 3.1 parts per million, the least concentration causing
irritation to eyes is 4.0 parts per million and the least concentration
causing coughing is 4.8 parts per million. A concentration of 0.02 – 0.05
percent is lethal to most animals in a few minutes, a concentration of 0.0025
percent is dangerous for exposures of 30 to 60 minutes. The maximum
concentration to which animals can be exposed for several hours without serious
symptoms is 1 part per million.
DISSECTION AND
DETERMINATION: The yellow or orange strain produced by phosgene on test paper
containing diphenylamine and p-dimethylamine benzaldehyde has been adopted as
the standard test for the detection of phosgene in Britain . The test is capable of
detecting about 1 part of phosgene in 10,00,000 of air (1 ppm).
RAPID METHODS: A
reagent filter paper is prepared by soaking it in a mixture of 5 c.c. of 0.5
percent solution of 1, 3, 3 – nitrosodimethyl aminophenol both in xylene. This
paper held in the suspected atmosphere gives a green colour with traces of
phosgene. If the paper becomes dry it should be moistened with alcohol before
use. It is said to be a specific reaction for phosgene.
A VERY SENSITIVE DROP
REACTION: Add a drop of phenylhydrazine cinnamate to a drop of the solution of
the suspected substance in chloroform or carbon-tetrachloride. After 5 minutes,
add a drop of 1 percent copper sulphate solution. The red-violet color of
diphenyl carbazide is formed in the presence of phosgene. As little as 0.0005
mg of phosgene can be detected by this method.
Phosgene forms
diphenyl urea when passed into an aqueous solution of aniline. Pass the
suspected air through about 3 cc of a saturated aqueous solution of aniline or
p-phenetioline. A white turbidity and then a crystalline precipitate forms in
the presence of phosgene. [See, The Analytical Chemistry of Industrial
Poisons, Hazards and Solvents, by Morris B. Jacobs, Ph.D., 1941,
Interscience pub., Inc., New York ,
pp 304-305 and 585-586, emphases ours].[1]
The foregoing
particulars irrefutably establish the most insidious nature of the War Gas –
Phosgene. Not for nothing was the Geneva Gas Protocol prohibiting the use in
war of asphyxiating, poisonous and other gases and of bacteriological methods
of warfare was signed by 42 nations on 17 June 1925 and is now being adhered to
by over 60 countries. Details of this aspect of human gas war will be given in
a separate article.
I don’t think, of
course, that any person in his senses would venture to dispute the above
authentic details about phosgene and its hazardous effects. But which one may
freely dispute, and that which the Union Carbide officials are doing, is the
fact of Phosgene being the real killer gas in this disaster. They are also
trying to suppress the information about and indications regarding this real
fact behind the Bhopal
According to the Statesman,
20 December 1984 (Thursday, Delhi Bhopal Saifia College ,
Bhopal
First: the physical
differences – MIC is a colorless chemical with boiling point of 39.1 degrees
Celsius at ordinary pressure. At the pressure in which it was stored in the
tank, 2½ times the pressure of the atmosphere, the boiling point would have
gone up to somewhere near 65o Celsius. The tolerance level of humans
for MIC is 0.02 parts per million in the atmosphere. According to Dr. Basha,
the gas, like the liquid, is colorless.
Phosgene is also
called Carbonyl Chloride, Carbon Oxy Chloride and Chloroformyl Chloride. Its
boiling point as stated earlier is 8.2o Celsius, and the gas is of light
yellow colour with a strong odour. Unlike MIC it is only slightly soluble
in water. Apart from being highly toxic with a tolerance level for humans of
0.1 ppm, it is an irritant to the eyes.
Dr. Basha pointed to
three significant points in these physical properties to illustrate his
argument. Firstly, he said, all victims said that they had seen the gas to
be light yellow. Secondly, all victims’ eyes had been affected.
While the effect of MIC on the human eye had not been proved yet, phosgene was known
to be an eye irritant. Thirdly, while Dr. Basha was willing to admit that MIC
in the storage tank might have been converted to gas due to an exothermic
reaction with water or due to polymerization, he wondered why it had not become
a liquid again when it came into the atmosphere since the temperature outside
was about 14 degrees Celsius (the same
argument we made in our previous article - IMS).
Dr. Varadarajan, who
had argued that the gas was only MIC, had said that its effects on the human
beings was that it reacted with the water in the lungs to produce dymethyl
urea CH.NH2, which is a harmless solid and Carbon-di-oxide,
which is again harmless. Dr. Varadarajan said that MIC kills because this
dimethyl urea clogs the passages that take air into the lungs.
The autopsies,
according to the CBI sources, had shown the evidence of this clogging, but it had
also shown that the most of the victims’ lungs were corroded as they would be
by an acid, thus strengthening Dr. Basha’s argument.
Dr. Basha said that
when phosgene reacts with water in the human lungs (or elsewhere) it produces
Carbon-dioxide and Hydrochloric acid, which would corrode the lungs. He also
said that in the lungs, due to relative shortage of oxygen, along with
Carbon-dioxide some Carbon monoxide would also be produced.
Now, it has been well
known that Carbon monoxide is poisonous, and as many people have been killed by
it, the scientists know exactly how it kills. Carbon monoxide gets into the
blood stream of the humans from the lungs where it destroys the red blood
corpuscles. The result is that the victims get drowsy, fall unconscious and
then die. Dr. Basha maintained that most of the victims had actually died in
that way. There was no confirmation from the CBI sources as to whether the
government physicians had found evidence of red blood corpuscles getting
destroyed.
In the Hamidia Hospital
We can only say Dr.
Basha had put up an excellent argument with which we almost fully concur. But
we are circumspect about his version of phosgene reaction in the lungs also
forming carbon monoxide due to the relative shortage of oxygen there. As you
see, none of the authorities we previously cited and who were well experienced
did take into account this possibility. Hence, if at all cases of carbon
monoxide poisoning were also there (the cases where red blood corpuscles were
destroyed), in our opinion, it should have been due to the escape of carbon
monoxide gas along with phosgene in that fateful night. This was quite possible
since carbon monoxide and chlorine go into the making of phosgene and were
present, stored in the Union Carbide plant. So this gives us the
possibility of three gases – phosgene, carbon monoxide and chlorine –
simultaneously escaping on that disastrous day. Hence here we take a little
diversion to give some details regarding CO and Cl2 also:
“Carbon monoxide is
met in any industry in which there is the possibility of incomplete combustion
of carbon compounds or carbonaceous material. Not only is carbon monoxide an
important industrial poison but it is also the greatest single non-industrial
hazard because it is a component of nearly all types of illuminating and
heating gases, it is a component of the exhaust gases of automobiles, and is a
probable ingredient of the fume gas produced by whatever form of heat is used
in domestic cooking – wood, coal, illuminating gas or oil.
For these reasons,
carbon monoxide is a hazard in the homes, private and public garages, workshops
and thereby polluting streets as well.
Carbon monoxide is a
colorless and odorless gas. It is combustible and is lighter than air having a
specific gravity of 0.967. [Even so, either because
its sp. gr. is subject to variations as per atmospheric moisture or due to some
other developments, at times it is found collected in deep wells even - IMS.]
Carbon monoxide in
excess of 0.01 percent if breathed for a sufficiently longer time, will produce
symptoms of poisoning. As little as 0.02 percent will produce slight symptoms
in several hours, 0.04 percent will produce headache and discomfort within 2 to
3 hours, with moderate excess 0.12 percent will produce slight palpitation of
heart in 30 minutes and a tendency to stagger in 1½ hours; and confusion,
headache and nausea in 2 hrs., a concentration of 0.20 to 0.25 percent will
usually produce unconsciousness in about 30 minutes. Its effects in high
concentration may be so sudden that a man has little or no warning before he
collapses.
Carbon monoxide is
really a chemical asphyxiant because it produces its harmful effect by
combining with the haemoglobin of the red blood cells forming a relatively
stable compound, carbon monoxide haemoglobin, usually abbreviated HbCO, thus
preventing this combined haemoglobin from taking up oxygen, forming
oxyhaemoglobin (HbO2) and thus depriving the body of its oxygen. The
affinity of carbon monoxide for haemoglobin is about 300 times that of oxygen.
Hence if only a small amount of carbon monoxide is present in the air taken
into the lungs, that carbon monoxide will be absorbed in preference to the
oxygen by the blood. Carbon monoxide asphyxia and probably other types of
asphyxia produce degenerative changes in nerve cells and [also] throughout the
entire brain.
The percentage of
haemoglobin in the blood combined with carbon monoxide instead of with oxygen
is termed ‘percentage of blood saturation’. Symptoms of poisoning [are] more or
less parallel to the blood saturation. The first decided symptoms during rest
make their appearance when 20 to 30 percent of the haemoglobin is combined with
carbon monoxide. Unconsciousness takes place at about 50 percent saturation and
death may occur at a saturation between 65 to 80 percent.
… [But] Carbon
monoxide is not as poisonous as many other industrial hazards. [See The
Analytical Chemistry of Industrial Poisons, Hazards and Solvents, by Morris B.
Jacobs, Ph.D., pp. 316-319].”
Again –
“Chlorine is a heavy
greenish-yellow gas which has a characteristic choking and pungent odour with
an irritating effect on the nose and throat. It boils at –33.6oC;
melts at –102oC; has a density of 2.5 referred to air; and can
easily be liquefied for its critical temperature is 146oC. Its
specific gravity is 1.41. Its vapor pressure at 20oC is 6.57
atmospheres, at 30oC is 8.75 atmospheres and at 40oC is
11.5 atmospheres. It has a high coefficient of expansion and its solubility in
water at 20oC is 215 volumes in 100 volumes.
Chlorine is a strong
lung irritant. It was the first chemical war gas
used in the World War I (1914-1918). A concentration of 2.5 mg per
litre breathed for 30-60 minutes will cause death. Inhalation of Chlorine
elicits respiratory reflexes and causes coughing, smarting of the eyes, a
general feeling of discomfort in the chest, a hoarse cough, nausea and
vomiting. The face may become red and bloated because of venous congestion, or
grey in color showing falling circulation. Inhalation of Chlorine affects both
the lower and upper respiratory tract and produces inflammation of the entire
respiratory tract and edema of the lung after severe exposure. The most
pronounced symptoms are suffocation, constrition in the chest and tightness in
the throat.
Concentration of 0.10
percent are lethal for animals in a few minutes. Exposure to a concentration
range of 0.004 to 0.006 percent for 30-60 minutes will have fatal or serious
consequences. The maximum concentration to which animals can be exposed for a
period of 60 minutes without serious disturbance is 0.0004 percent and the maximum
concentration to which they may be exposed for several hours without serious
disturbance or with but slight symptoms is 0.0001 percent by volume (i.e. 1
part per million – author).” (Ibid., pp.
295-296, emphasis ours).
We cannot rule out the
possibility of carbon monoxide and chlorine also leaking along with phosgene in
that fateful night, but it seems phosgene is the main culprit – the real killer
gas – that played havoc.
India Today, 31
December 1984, has revealed some details which substantiate our arguments
regarding Phosgene:
“M.L. Garg, retired
brigadier and general manager of the paper factory, Straw Products Ltd., was
asleep that night when the telephone rang at 1-15 a.m.
It was the factory
calling to say some people had fainted: “We are suffocating, Sir,” the voice
said. Just then, Garg recalls, his eyes began to water and he himself
suffocated. The windows of his house were open and he soon saw a ‘yellow
gas’ waff in.” (emphases ours)
Again –
“Shazad Khan, a tanker
driver aged 30, too was asleep with his wife and four daughters in Jayaprakash
Nagar which also borders the factory. “Main
jaaga aur ankhon mein ek dam jalan mehsoos huyi, jaise ke koi nazar utaar rahe
ho,” he said [I awoke, my eyes began smarting, as if some had flung
chillies into fire to ward off evil eye]. In wild panic, Shazad fled
from his room.” (emphasis ours)
It is quite evident
from these reports that the colour of the gas was yellow and it is a strong eye
and lung irritant. Again, as the fortnightly reports, Chairman Warren Anderson
of the Union Carbide in the US
One of the lapses to
which the report clearly pointed was “the pressure gauge on the phosgene
tank was bad, showing no pressure even though the tank was in service” (emphasis
ours). Now it is doubly clear that not only
phosgene was used, a separate tank was there in the plant for its storage. Then
the same issue of India Today graphically discusses the defects in safety
system, poor training and education of the personnel, even the lack of
requisite number of workers to maintain the installment, etc. However here it
would do for us to emphasize that the presence, storage and leakage of phosgene
is proved beyond doubt by all the evidence obtained so far.
Now we would like to
go into some detail about the production process in the Union Carbide plant at Bhopal Bhopal
CARBARYL
Function: Insecticide.
Chemical name: l
naphtalenyl methyl carbamate
Formula: O
CO NH CH3
Trade name: Sevin ® (Union
Carbide)
Manufacture: In a first step, sodium l-naphthoxide is reacted with
phosgene –
And in a second
step, that intermediate is reacted with methyl amine to give l-naphtyl-N-Methyl
Carbomate…
[See: Pesticides
Process Encyclopedia, by Marshall Sitting, Noyes Data Corp., Park Ridge , New Jersey , USA
However, as already
mentioned, the production process has changed since 1978 and Methyl Isocyanate
is produced and used up as an intermediate product in the new process. This
takes us to some details about the production and uses of isocyanates and after
delving into those aspects, we finally go into the details about the production
process and uses of phosgene itself.
“ISOCYANATES, ORGANIC:
Phosgene reaction: In
1884, Hemtschel obtained an isocyanate from the reaction between phosgene and
the salt of a primary amine. Several modifications of this reaction have since
been developed. This reaction is especially useful for high boiling isocyanates
and di-isocyanates, which may be prepared readily and in good yields by the
reaction of a slurry of the amine hydrochloride with phosgene in toluene or
di-chlorobenzene…
Manufacture and
Processing:
Phosgenation: The
reaction of amines with phosgene (phosgenation) has, for economic reasons,
been used almost exclusively for the manufacture of isocyanates. The details of
processing may vary with the specific isocyanate and, in particular, for
aromatic and aliphatic isocyanates (MIC is an
aliphatic isocyanate - IMS), but the general approach is the same.
Because of several side reactions and associated complications, the development
of practical, high yield reaction conditions have been studied extensively. The
primary reactions involved in the phosgenation of a simple amine and the
further reactions [simply put indicate that] reaction with primary alkyl and
aryl amines yield carbamoyl chlorides which can be de-hydrohalogenated to
[yield] isocyanates… [See: Encyclopedia of
Chemical Technology, Third edition, Vol. 17, by KIRK-OTHMER].” (emphases
ours)
Hence, it is quite
evident that all isocyanates (including MIC) are produced by a process of
phosgenation for economic reasons. All the reaction equations in this
regard reveal that they are consummated under 200oC which is a
fairly low temperature as far as industrial processes are concerned and so
quite economical at that. Also we have learnt that all isocyanates and
di-isocyanates are high-boiling liquids and in fact it is MIC which has the
lowest boiling point (39.1oC) among them all. [See appendix 3 –
Physical properties of some Isocyanates].
Further –
“There are five
aliphatic isocyanates of commercial significance, although none approach the
volume of TDI (Toulene Di-isocyanate) or the polymerics. Methyl Isocyanate is
produced by the Union Carbide. Several insecticides and herbicides are derived
from this isocyanate, including the widely used l-naphthyl carbamate sold under
the trade name, Sevin. It is estimated that 12,000 - 14,000 metric tons of
methyl isocyanate was produced in the U.S. in 1975 and 24,000 tons of
Sevin. About half of the Sevin was exported. Growth to 23,000 tons of
isocyanate is predicted for 1980. Methyl isocyanate is believed to account
for about three quarters of all mono-isocyanates manufactured.”
“HEALTH AND SAFETY:
All isocyanates are
potentially hazardous and require care in handling. They are lacrimators and
may have a mild tanning action on skin, but the primary health effect is
respiratory irritation caused by isocyanate vapors. In 2.5% of population that
is exposed to low concentrations of isocyanate vapor, a hyper sensitive, asthma
like allergic reaction may result. Skin allergies have been observed but are
not common. In general, the lower the vapor pressure, the fewer the problems in
its use, but adequate ventilation should always be employed…” [Encyclopedia
of Chemical Technology, op.cit., emphasis ours]
Now it is significant
that though every victim in Bhopal
“MANUFACTURE:
Depending on the quantity needed and the availability of the raw material,
numerous variations of the basic synthetic process are being practiced. Continuous
processing and high degree of automation is required for phosgene
purification, condensation and storage. Because of its toxicity, careful and
extensive safety procedures are incorporated in plant design and operation.
The manufacture of phosgene consists of preparation and purification of carbon
monoxide, preparation and purification of Chlorine, metering and mixing of
reactants, reaction of mixed gases over activated charcoal, purification and
condensation of phosgene and recovery of traces of phosgene to assure worker’
and environmental safety.
After condensation,
the remaining product gases are scrubbed with caustic soda (NaOH) solution
(Caustic scrubber system) to destroy any non-condensed phosgene.
STORAGE AND HANDLING:
All phosgene containers require the class A poison gas label. Phosgene
is transported in steel cylinders which conform to rigid safety design
specifications. The cylinders undergo special hydrostatic testing at 5.5 Mp
(800 psi), and extension rings are incorporated in the cylinders to protect the
Valves; ……
Careful testing for
leaks is required after filling and vapor space must be accommodated in the
storage vessel; excessive filling with liquid phosgene must be avoided.
Because phosgene
reacts with water, great care must be taken to prevent contamination with
traces of water since this could lead to the development of pressure by HCl and
CO2. Wet phosgene is very corrosive; therefore, phosgene should
never be stored with any quantity of water.
HEALTH AND SAFETY
FACTORS: The odor threshold for phosgene is circa 0.5 - 1 ppm, but it varies
with individuals and is higher after prolonged exposure. Phosgene may irritate
eyes, nose and throat. The permissible exposure TLV by volume in air is 0.1
ppm. The TLV refers to the airborne concentration at which it is believed
nearly all workers may be repeatedly exposed on a daily basis without adverse
effect…
Hazards can be avoided
by the use of outdoor installations or extensive ventilation where phosgene
must be employed indoors. Ventilation should be sufficient to maintain general
concentrations of phosgene in the air below 0.1 ppm, even though liquid
phosgene is released. Safety in handling phosgene depends to a great extent
on the effectiveness of employee education, proper safety instrumentation,
alert supervision, and the use of safe equipment. Plant design should include
proper facilities for neutralization and water-fog equipment should be
available for emergencies.
In case of extensive
leaks or spills, immediate evacuation upwind of the phosgene source is
necessary. Phosgene is 3.4 times as heavy as air and may collect in the
low-lying areas. Water should not be used on the source of a phosgene leak
as the resulting corrosion enlarges the leak. Suitable protective equipment
includes eye-protection and respiratory equipment. In case of fire, it is
essential to cool all phosgene-containing vessels. Reactivity hazards exist
when attempts are made to neutralize spilled liquid phosgene. Especially
hazardous chemical reactions of phosgene are with alcohols, Aluminum, Secondary
Amines, Potassium and Sodium.
USES: Phosgene is an
important and widely used intermediate. Practically all phosgene manufacture is
captive i.e. it is used in the manufacture of other chemicals within the plant
boundary. Its toxic hazard has created some difficulty in plant-location
approvals and has caused the shut-down of a European facility. [See: Encyclopedia of Chemical Technology, Vol. 17,
KIRK-OTHMER, Third Edition, pp. 416-425, emphases ours.]
So, now, we have ample
information about the production process of phosgene, MIC and the hazards posed
by them and the necessary safety measures to be taken up. Especially safety in
handling is reported to depend to a great extent on the effectiveness of
employee education, proper safety instrumentation, alert supervision and the
use of safe equipment. In this particular case of the Union Carbide plant at Bhopal India Union
and State Governments has much to do with this recruitment of ineligible and
untrained personnel. Moreover, Mr. Vijay Gupta, the legal advisor of the U.C.
plant is said to be a Congress-I leader and close supporter of Chief Minsiter,
Arjun Singh. A nephew of the former Education Minister Mr. Narsingrow Diskhit
is a public relations officer of the U.C. plant. The company’s guest house at
Shyamala Hills was always at the disposal of the Chief Minister Arjun Singh
(see Indian Express, 5-12-1984). This political clout of the company was
the cause for degeneration in the recruitment of personnel as well as for the
defence of its misdeeds by the M.P. and the Union Governments. Even the report
of the three US experts
regarding the safety measures in the plant found much fault with the safety
system there and it is now well-known that the plant at Bhopal
did not have the computerized safety-warning system which was installed in the
mother-plant in West Virginia , U.S.A. Union and
the State Governments as well as to the people in general. We have already
learnt that practically all phosgene manufacture is captive i.e. it is
used in the manufacture of other chemicals within the plant boundary. This
implies that phosgene is not to be stored for long times, but has to be
produced as and when required so as to be immediately used for further
processing. This ought to be the same case with MIC also. But all these
restrictions in case of both these intermediate products seem to have been
thrown to winds – all rules and regulations in this regard seem to have been
blatantly violated. Even the fact of MIC production was sought to be suppressed
and at first the Union Carbide management circulated the big lie that they are
importing the MIC. But when this lie was refuted by its own mother corporation
in the USA Union and the State governments and also by
the monopoly capitalist press of our country. Most of the scientists, chemists,
doctors and other experts are also discreetly silent on this aspect. In such a
situation where the very presence and production of phosgene is being denied by
the UC people, one can in nowise expect its employees to possess any adequate
knowledge about the great hazards that killer gas poses and the ways and means
to counter such hazards. As to the lakhs of innocent people of Bhopal Union or State
Governments. The people of our
country have to rise to the occasion and fight vigorously for realizing the
above demands. Of courts, it is quite true that it would not suffice even if
all these demands are conceded and what is especially needed is a total change
in the present policy of industrialization. A real humanity oriented and labour
intensive industrialization process, with adequate protection to the existing
environment, is the need of the day and this involves bitter struggle against
the multinationals, and their Indian touts and allies. The sham Socialist
measures of the Union and State Governments
which only develop private capitalism and drive for money-making more and more
have to be countered and effectively fought. But first things first please. Let
us first concentrate on the immediate demands ensuing from this unprecedented
holocaust in Bhopal
Dated: January 1985.♣ CONVENER,
MARXIST STUDY FORUM,
6-3-1243/116, D. Sanjeevaiah Nagar
(M.S. Makta),HYDERABAD - 500 082.
6-3-1243/116, D. Sanjeevaiah Nagar
(M.S. Makta),
* * * * *
APPENDIX 1:
PHOSGENE
COMMON NAME
|
…
|
PHOSGENE
|
Chemical Name
|
…
|
Carbonyl Chloride (COCl2)
|
Persistency,
Summer
Persistency, Winter
|
…
…
|
5
mts. Open, 10-20 mts. in woods
10 mts. Open, 30 mts. in woods
|
Tactical Classification
|
…
|
Casualty agent.
|
Physiological classification
|
…
|
Lung irritant – choking gas.
|
Odor in air
|
…
|
Like ensilage – fresh-cut hay.
|
Melting point
|
…
|
–118o C (–180o F)
|
Boiling point
|
…
|
8.2o C (46.7o F)
|
Volatility at 20o C (68o F)
|
…
|
6,370 oz./1,000 cu. ft. air.
|
Vapor density compared to air
|
…
|
3.4
|
Vapor pressure at 68o F
|
…
|
1180 mm. of mercury.
|
Density of liquid at 20o C (68o F)
|
…
|
1.37
|
Solvents for
|
…
|
Cl and PS.
|
Action on metals
|
…
|
Dry, none; wet, vigorous corrosion
|
Stability on storage
|
…
|
Stable in dry steel containers.
|
Action with water
|
…
|
Hydrolizes rapidly.
|
Hydrolysis product
|
…
|
HCl and CO2.
|
Physiological action
|
…
|
Burns lower respiratory tracts; causes edema.
|
First Aid
|
…
|
Keep patient quiet and warm; give oxygen in severe
cases; treat like pleurisy; administer heart stimulants; treat as stretcher
case.
|
Odor detectable at
|
…
|
0.005 oz./1000 cu. ft. air.
|
Minimum irritating concentration
|
…
|
0.005 oz./1000 cu. ft. air.
|
Lethal concentration
|
…
|
10 minute exposure 0.5
oz./- 1000 cu. ft. air.
|
Method of neutralizing
|
…
|
Steam hydrolyzes, alkalies and amines react with CG.
|
Munitions suitable for use
|
…
|
Livens projector shell; cylinders; chemical mortar;
large airplane bombs.
|
Marking on munitions
|
…
|
1 green band – CG gas.
|
Protection required
|
…
|
Gas mask.
|
* * * * *
APPENDIX 2:
CHLORINE
COMMON
NAME
|
…
|
CHLORINE.
|
Chemical
Name
|
…
|
Chlorine
(Cl2)
|
Persistency,
Summer
Persistency,
Winter
|
…
…
|
5
mts. in open, 20 mts. in woods
Same
as in Summer.
|
Tactical
Classification
|
…
|
Casualty
agent.
|
Physiological
classification
|
…
|
Lung
irritant – choking gas.
|
Odor
in air
|
…
|
Pungent.
|
Melting
point
|
…
|
–102o
C (–152.5o F)
|
Boiling
point
|
…
|
–33.6o
C (–28.5o F)
|
Volatility
at 20o C (68o F)
|
…
|
19,369
oz./1,000 cu. ft. air.
|
Vapor
pressure at 68o F
|
…
|
4993
mm. of mercury.
|
Vapor
density compared to air
|
…
|
2.4
|
Density
of liquid at 20o C (68o F)
|
…
|
1.4
|
Solvents
for
|
…
|
CG,
PS, CCl4.
|
Action
on metals
|
…
|
None
if dry; vigorous corrosion if wet.
|
Stability
on storage
|
…
|
Stable
in iron cylinders.
|
Action
with water
|
…
|
A
little dissolves, forming HCl; and.
|
Hydrolysis
product
|
…
|
HCl;
HOCl; ClO2.
|
Physiological
action
|
…
|
Burns
upper respiratory tracts.
|
First
Aid
|
…
|
Keep
patient quiet, warm and treat for bronchial pneumonia.
|
Odor
detectable at
|
…
|
0.01
oz./1000 cu. ft. air.
|
Minimum
irritating concentration
|
…
|
0.03
oz./1000 cu. ft. air (irritates throat).
|
Lethal
concentration
|
…
|
10
minutes’ exposure 5.6 oz./- 1000 cu. ft. air.
|
Method
of neutralizing
|
…
|
Alkali,
solution or solid.
|
Protection
required
|
…
|
Gas Mask.
|
* * * * *
APPENDIX 3:
Physical Properties of
some Isocyanates
Compound
|
Formula
|
CAS Registry No.
|
Mp, oC
|
Bp, oC
|
Density,
g/cm3 |
Refractive index, nb
|
Flash point, open cup, oC
|
Methyl isocyanate
|
CH3NCO
|
[624-83-9]
|
…
|
38101
|
0.96204
|
1.3620
|
–7
|
4,4’-diphenylmethane
diisocyanate
|
 |
[The detailed
table considered not necessary for the purposes of this article - IMS.]
¨ Convener, Marxist Study Forum, Hyderabad;
Also Convener, Telugu Jati Aikyata Vedika (Telugu National Unity Forum) and
Life Member, People’s Union for Civil Liberties. Advocate practicing in the
High Court of Andhra Pradesh, Hyderabad
and also Editor, LAW ANIMATED WORLD.
[1]
Unfortunately, not a single official or any person of civil society had either
the responsibility or the presence of mind to collect samples of this fatal gas
cloud which was slowly passing through the localities of Bhopal for hours
together - IMS.
♣ This detailed article has been written
and circulated to select persons sometime in January 1985 itself but now
updated on 07-07-2010. The author was also General Secretary, PUCL, AP, at that
time but now is only a life member of PUCL. He continues to be the Convener,
Marxist Study Forum.
