PROPORTION OF CHEMICALS. 33 



siderable excess of sulphuric acid present. It is perfectly possible, however, that 

 this excess of sulphuric acid is of value in heating up the mixture so that more of the 

 hydrocyanic acid is liberated and not absorbed by the liquid." 



The results of some tests serve as a further illustration of this 

 point. It was desired to determine by experiment if 1 fluid ounce of 

 acid to each ounce (avoirdupois) of cyanid would be sufficient to 

 carry the reaction to completion in the liberation of hydrocyanic- 

 acid gas. It is to be understood throughout that the cyanid ounce 

 is avoirdupois and the acid and water is the fluid ounce. For this 

 test two series of ordinary IJ-gallon fumigating vessels were placed 

 in line. In one series equal parts of acid and cyanid were used. 

 Three parts of water were used in all cases. The amounts of cyanid 

 used ranged from 1 to 10 ounces, that is, in one generator were 

 placed 1 ounce of cyanid, 1 ounce of sulphuric acid, and 3 ounces of 

 water; in the next of the same series, 2 ounces of cyanid, 2 ounces 

 of sulphuric acid, and 6 ounces of water, and so on in the same pro- 

 portion up to 10 ounces. The second series was identical with the 

 first except for the use of one-fourth more acid than cyanid. After 

 generation had taken place for about one and one-half hours an 

 examination was made of the residue. In the first series, in which 

 equal parts of acid and cyanid were used, the residue was in the 

 form of a liquid. In the second series, in which 1\ ounces of acid to 

 1 of cyanid were used, the residue in several pots had collected in a 

 mushlike mass. Being puzzled at first over this phenomenon, in 

 order to ascertam if cyanid still remained unchanged in the residue 

 the writer added more sulphuric acid, but there was no further evolu- 

 tion of gas. This at once demonstrated that all the available cyanid 

 had been dissolved. Analyses of this residue by J. K. Haywood of 

 the Bureau of Chemistry showed that the reaction was complete both 

 when 1 ounce of acid and when 1\ ounces of acid to 1 of cyanid were 

 used. In submitting the result of these analyses. Dr. H. W. Wiley, 

 Chief of the Bureau of Chemistrj^, wrote: 



The amount of cyanid present in these samples is so small that it does not indicate 

 to us incompleteness of reaction, but rather indicates the amount of hydrocyanic acid 

 dissolved in the residue. This view of the case is strengthened by the fact that 

 increasing the amount of sulphuric acid in the cases above did not decrease the amount 

 of cyanogen present in the residue. From our work, therefore, we are of the opinion 

 that the same amount of sulphuric acid as of potassium cyanid is sufficient to carry 

 the reaction to completion. 



a In an address printed in the Proceedings of the Thirty-fourth Annual Fruit Grow- 

 ers' Convention of California, p. 103, the proportion of chemicals spoken of appears 

 somewhat different from that mentioned in this publication. This is due to the fact 

 that the parts mentioned in that address were based on parts by weight of acid and 

 cyanid, both of which are chemically pure — not the commercial product as given in 

 this bulletin. 



77488— Bui. 79—09 3 



