The successful treatment of two recent cases of cyanide poisoning.

It has long been recognized that hydrogen cyanide with its sodium and potassium salts is one of the most potent and rapidly acting poisons. In spite of this, the cyanide salts have been used industrially, especially in gold mines to extract gold from the ore, for very many years. The case hardening of metals and electroplating processes also depend on the use of cyanide salts in considerable quantities, and during the past 30 years hydrogen cyanide itself, which was hitherto only regarded as a laboratory chemical, has come into prominence industrially, first as a fumigant, and later in relatively large quantities in chemical processes for the manufacture of plastics. The acid is very much more dangerous than its salts, owing to its high volatility and the extreme toxicity of small amounts when inhaled in the form of vapour. An atmosphere containing less than 500 parts per million can be breathed by man for only one minute without fatal results, and breathing apparatus is necessary whenever the concentration of the gas is likely to exceed 100 parts per million (Occupation and Health, 1930). The number of accidents from hydrogen cyanide poisoning in factories in Britain is surprisingly small, and it is to the credit of the safety organizations in industry that only 19 such accidents were reported between the years 1921 and 1948, four of which were fatal (Merewether, 1949). It has to be remembered that these figures refer only to accidents in factories, and reference to the Registrar General's return for England and Wales for the years 1933-47 shows that there were, during that period, 18 deaths from cyanide gassing and 38 deaths due to other accidental cyanide absorptions. The 18 deaths from gassing probably contain several which were due to the use of hydrogen cyanide as a fumigant, and it is, therefore, interesting to note that a considerable number of such deaths occurs in places where the Factories Act does not apply. United States figures indicate, as would be expected, that the majority of deaths from cyanide poisoning have been suicidal, but that fatalities from hydrogen cyanide are more frequently accidental than suicidal. One hundred and twenty deaths of an accidental nature are reported between the years 1933 and 1941 from gaseous hydrocyanic acid (Chen, Rose, and Clowes, 1944). It is obvious that the opportunity to try newer methods of treatment of cyanide casualties has been much greater in the United States than in Britain, and a search of the available literature confirms the fact that this opportunity has not been disregarded.