Tuesday, January 28, 2014


- I. Mallikarjuna Sharma¨
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.
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 holocaust and sadly, even a majority of the experts, journalists, etc. of our country are also joining their bandwagon. To establish that Phosgene is the real culprit gas, we have, in the last article, pointed out that Methyl Isocyanate, which is only a liquid that becomes a gas at circa 40oC could not be cause for the holocaust since the atmospheric temperature in that fateful night in Bhopal was around 14oC only. We also concluded that since most of the deaths were reported due to edemal of lungs and consequent asphyxiation the killer gas could be nothing but the dreaded Phosgene. Since then a lot of positive evidence has come out to irrefutably establish the identity of the killer gas as Phosgene.

According to the Statesman, 20 December 1984 (Thursday, Delhi), the admission by Dr. S. Varadarajan on Tuesday evening that there was some phosgene in the Union Carbide plant after his stout denial of the fact for the past three days has once again brought into focus the question of whether the poisonous gas that leaked out and killed thousands of people in Bhopal was phosgene or MIC or sum of both. “If the gas was phosgene or a mixture of MIC and phosgene, it would show that the Union Carbide management in Bhopal had been guilty of not only acts of criminal negligence, but also gross criminal violation of their own rules.” (emphasis ours). The same edition of the Statesman also reports: “One of the staunchest proponents of the theory that it was phosgene that leaked out is Dr. S.G. Basha, of the Chemistry Department in the Saifia College, Bhopal. He went into great details of comparative chemistry of the two poisonous chemicals to illustrate the point.
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, where most of the victims had been admitted, there was no agreement among doctors on this point whether the killer chemical was phosgene or MIC. Those who were for MIC said that the victims had died either due to constriction of their air passages or later due to pneumonitis (both of which are quite possible with phosgene poisoning too as evidenced by extensive quotations cited above), while the others gave out the same arguments as Dr. Basha.
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 released a report submitted in mid-1982 by three American experts who inspected the Bhopal Plant’s safety measures and equipments. The report was startlingly critical saying that “the plant represented either a high potential for a serious accident or more serious consequence if an accident should occur” – words which proved all too correct in retrospect even though it was claimed that most of the defects have been set right in just this year.”        (emphasis ours)
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. These details will again establish the presence, production and storage of phosgene in the plant. The Union Carbide plant at Bhopal produces two pesticides – Sevin and Temick (trade names). Sevin is the world’s most widely used pesticide and naturally a great part of the production in the Bhopal Unit is that of Sevin only. It is also called Carbaryl. Prior to 1978, they used to manufacture Sevin without recourse to MIC (but necessarily with recourse to phosgene) and possibly since 1978 or 1980, they switched over to the more economical process through the use of MIC. We hereunder give some details about Carbaryl produced without recourse to MIC:
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, 1977).
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.
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.”
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 complained of irritation in the eyes, the phenomenon of lachrymation (tears flowing) is not reported that commonly. Further as Sunday reported, the killer gas affected people up to a 10 Km. radius from the Plant Centre and people falling within 5 Km. radius were severely affected. This is simply out of question with regard to MIC ‘gas’ since any MIC converted into gas due to unforeseen high pressures and temperatures developed in the plant, would have immediately cooled down and liquefied in the around 14oC temperature in Bhopal in that night and consequently it could not have affected people beyond a radius of 1 Km. under any circumstances, that too when the wind speed in that night was quite low and it was reported that the gaseous cloud was traversing very slowly all along. So, the brilliant arguments of Prof. S.G. Basha, coupled with our own reasoning and additional arguments, conclusively establish the identity of the killer gas as phosgene. Hence it will be apt here to go into the details of the phosgene manufacture and the necessary storage and safety measures, its uses, etc.
“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, we find each of these requirements in effective absence. India Today (31 December 1984) reports thus: “In 1977-78, when work on the MIC plant started, only first class B.Sc. graduates or those with a diploma in engineering were taken as operators. They were subjected to six months’ theoretical training and then trained on the job. That is no longer true, and there are cases of operators without an academic science background and, what is more, they no longer have to undergo the same rigorous training as before. Some operators are matriculates from other plants or units. Worse still, the number of staff has been cut down because of financial problems.” It is quite possible that the secret deals of the Union Carbide management with the 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. Moreover, the way in which the Union Carbide Management is going all out to deny any presence of phosgene inside the plant raised many an eyebrow. Even Dr. Varadarajan of CSIR, who otherwise was so willingly obliged to the UC people in declaring that it was MIC ‘gas’ which was responsible for the killings, had to admit the presence of phosgene in the plant. This only implies that the U.C. people have been hiding the fact of phosgene production from the beginning and they lied in this respect to the 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, they had to admit the fact of indigenous production of MIC, but regarding the presence and production of phosgene they are still lying. This is because once they admit this fact they would be in for many-a-trouble, even international censure for their criminal negligence, criminal violation of international regulations and criminal acts of deceit and lying. So naturally they want and try their best to suppress this fact and put the sole blame for the disaster on the MIC ‘gas’. In this hideous maneuver they are being actively assisted by the 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 one can only guess the holocaust to which they were subject due to the havoc played by a gas against which even professional soldiers were advised not to take any chances. That there have been annual accidents in Bhopal plant ever since it started its production in 1980, that on 26 December 1981, a plant operator Mohammed Ashraf was killed following a leakage of phosgene gas, and that a local journalist Raj Kumar Keshwani has written soul-stirring appeals in his ‘Rapat Saptahik(Weekly Reporter) and also in ‘Jansatta’ about the impending disaster are too well-known to be enumerated in detail. That the political clout of the company saved it each time and that the then Labour Minister Tarasingh Viyogi had so superciliously told Mr. Mahendra Karma, MLA, in the State Assembly in December 1982 that a sum of Rs. 25 crores had been invested on the plant, that it was not a small stone to be shifted elsewhere and that there was no danger to Bhopal nor would there be any in future are also equally well known. This only enhances the culpability of the State Government of Madhya Pradesh many times over and it is only reasonable that it should have at once resigned in the wake of such a holocaust. But since the Chief Minister Arjun Singh still unashamedly continues in office, it is quite correct on our part to have demanded his dismissal; likewise the Union Industries and Chemicals Ministers cannot also escape from their culpability and they too ought to quit. This being the worst industrial disaster in the world, it is only just and reasonable that an International Commission of Inquiry be ordered at once and the United Nations help and guidance immediately sought. Also the entire assets of the Union Carbide Corporation have to be immediately confiscated by the 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 and in course of time work for more just, egalitarian and humanity conscious policies, programmes and system.

Hyderabad,                                      I. MALLIKARJUNA SHARMA
Dated: January 1985.                     CONVENER, MARXIST STUDY FORUM,
6-3-1243/116, D. Sanjeevaiah Nagar 
                                                                  (M.S. Makta), HYDERABAD - 500 082.
* * * * *

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
Vapor pressure at 68o F
1180 mm. of mercury.
Density of liquid at 20o C (68o F)
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.

* * * * *
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
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
Density of liquid at 20o C (68o F)
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.
* * * * *
Physical Properties of some Isocyanates
CAS Registry No.
Mp, oC
Bp, oC
Refractive index, nb
Flash point, open cup, oC
Methyl isocyanate

4,4’-diphenylmethane diisocyanate
File:4,4'-methylene diphenyl diisocyanate.svg

[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.

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