Correspondence THE DISCOVERY OF THE ELEMENTS. 111. A CORRECTION To the Editor DEARSIR: In Part I11 of the series of articles on the above subject [J. CHEM. EDUC.,9, 23 (Jan., 1932)], I have stated that in the eighteenth and nineteenth centuries Sweden far outstripped all other countries in the discovery of new elements. In the light of further study it is now apparent to me that this is too broad a statement. Sweden undoubtedly led in this field of research during the eighteenth century, and Swedish chemists continued to make numerous brilliant discoveries of elements throughout the entire nineteenth century. In the meantime, however, British chemists, including Wollaston, Tennant, Davy, and Ramsay, were discovering elements not singly but in groups, while French and German efforts were also being crowned with success. Because of varying criteria as to what constitutes the discovery of an element, and because of the many cases of independent discovery, it is not possible to assign a definite number of chemical elements to the credit of each country. I wish to thank the JOURNAL OF CHEMICAL EDUCATION for this opportunity to correct a statement which would otherwise be open to criticism. Sincerely yours, THEUNIVERSITY OF KANSAS LAWRENCE, KANSAS r MARYELVIRAWEEKS
CHEMICAL HAZARDS IN FIRE-FIGHTING To the Editor DEARSIR: EDUCATION (pp. The September, 1932, issue of the JOURNAL OF CHEMICAL 1523-9) contains an article on the "Hazards in Fire-Fighting," in which the author includes many referencesto the compressed gases, some of which are apt to leave the reader with false impressions of the integrity of commercial gas containers and their action when involved in a fire. The statement is not justified by experience that "of all the chemical hazards involved in fires, perhaps those presented by the gases are as a class the most difficult to handle." It is an exceptional case if a cylinder of compressed gas involved in a fire explodes and there are few references on record of this having happened. On the other hand numerous instances are known where cylinders involved in fires have released their contents 2127
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gradually through the functioning of their safety devices, preventing the development of pressures that might have caused cylinder failure. Neither is the statement justified that "increase in pressure because of increasing temperature may be so much more rapid than the decrease in pressure brought about by the small relief hole, that the cylinder will blow up." The safety devices in compressed gas cylinders are not make-shift arrangements but are carefully designed and tested instruments that must comply with the regulation of the Interstate Commerce Commission requiring gas cylinders to be ". . .equipped with one or more safety devices approved as to type and location by the Bureau of Explosives and found to prevent explosion of the normally charged cylinder when it is placed in a fire." The gas manufacturer hm to prove the adequacy of the number and type of device used on his equipment, by actual fire tests, to the Bureau of Explosives from whom approval must be obtained-before the device or devices may be used. When the safety device functions on a cylinder, involved in a fire, containing a flammable gas, or a gas that is a supporter of combustion, the ignition of the gas by the existing fire only contributes to the hazard of the fire by adding intensity to the blaze until the gas is consumed. Such gases as argon, helium, nitrogen, and carbon dioxide are inert, non-flammable gases and assist in retarding the progress of a fire. Carbon dioxide, erroneously referred to as poisonous, is not poisonous in any concentration. It is a harmless gas when breathed in small quantities but, like the other inert gases mentioned, i t is suffocating in high concentrations in the sense that it excludes from the lungs oxygen necessary to support life. Most of the gases referred to by the author as being noxious, and therefore adding additional hazard if involved in fire, are flammable and are rendered innocuous in burning. Chlorine is mentioned as a poisonous gas but the industry takes issue with this statement. Chlorine is not poisonous in the sense that toxic gases are considered poisonous. It is an irritating gas and has a harmful effect upon the lungs and other respiratory tissues. It is not absorbed into the blood as are the toxic gases. Continuous exposure may be fatal only because of the contraction of the respiratory tract. Neither is methyl chloride considered a poison or toxic gas. It is better classified as an anesthetic gas whose flammability places it with the gases rendered innocuous by burning. Carbon monoxide is not a commercial compressed gas and there is no provision in the Interstate Commerce Commission Regulations for its storage and transportation. It might be encountered in chemical laboratories where it is prepared for immediate use but i t is not prepared or shipped commercially.
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The compressed gas industry owns some five million or more pressure containers used. for the storage and transportation of their products. These containers are equipped with safety devices designed to prevent the hazard of failure under any condition that would raise the temperature or pressure of the content to a predetermined maximum. The adequacy of these safety devices to prevent failure of the containers under abnormal conditions is passed upon by the Bureau of Explosives, an independent agency representing the Federal Commission having regulatory power. The adequacy of these devices is further attested to by the accident record of the industry as reported by the Bureau of Explosives in their 1931 annual report. This report shows only $65.00 worth of property damage was incurred on all the railroads within the United States and Canada. No one was injured. While this is not a specific reference to accidents caused by fires, i t does illustrate the point that with millions of these cylinders in circulation, safety devices have prevented cylinder failures in transportation and confined the damage from gases to a few minor leakages. Very truly yours, F. R. FETHERSTON, Secretary COMPRESSED GASMANUFACTURERS' ASSOCIATION 110 WEST40ra ST.,NEWYonK CITY
To the Editor
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DEARSIR: The statement by Mr. Fetherston that the safety devices in gas cylinders are not makeshift arrangements, of course, is true. Under any normal conditions of storage or transportation even the most poisonous and explosive gases are being handled safely. There are, no doubt, many fires in which cylinders of gas do not explode because of rapid expansion of the gas. I have no data as to the number of cases in which explosions have occurred, knowing personally of only two specific instances. If the cylinder of gas is in a fire of sufficientintensity of heat that it is rapidly heated the pressure developed would be enormous in spite of the lowering of pressure from escape through the relief hole and might become sufficient to cause rupture of the cylinders. Even if this occurrence is rare it is still a hazard which should he considered in fire-fighting. When a flammable gas is released from a cylinder in a fire it may bum quietly or because of temporary deficiency of oxygen or lack of immediate contact with the flame it may collect in considerable quantities and when ignited do so with explosive violence. This means, then, that cylinders containing explosive gases may add considerably to the hazards of fire-fighting.
