Neav York Agricultural Experiment Station. 305 



cases the latter interfered with rapid emptying and refilling of 

 generators. Where the chemicals were used in the proportion 

 of 1-1-8, the action was entirely too slow on the ordinary size 

 >of broken cyanide. In some instances it was not even complete 

 in the period allowed for fumigation of a tree. 



The use of equal amounts of acid and water, even though 

 greater than the amount of potassium cyanide, did not give 

 increased chemical action. 



The use of an excess of acid and three times as much water 

 did not materially decrease the rate of chemical action. 



In general the table shows that a slight excess of acid and 

 two to four times as much water gave fairly good results, but 

 in cases where powdered potassium cyanide was used the chem- 

 ical action was violent enough to throw the contents out of the 

 generator. 



OONCLUSION. 



It should be observed that the smaller the pieces of potassium 

 cyanide the less time required for chemical action, no matter 

 what ratio of acid and water was used. By the use of one and 

 a half times as much acid and three times as much water as of 

 potassium cyanide, by volume, the action was nearly as rapid 

 with large pieces as with small pieces when used with less acid 

 and water. 



Where large quantities of potassium cyanide are broken fine 

 there is a waste not only by decomposition on exposure to the 

 air but also by its being thrown out of the generator when 

 chemical action begins. Having it broken to a definite size, as 

 some have recommended means an additional expense of 2 cents 

 per lb. on wholesale price, but by using the finely broken 

 potassium cyanide and an equal amount of sulphuric acid by 

 volume the total cost per charge of chemicals is the same as 

 where ordinary broken cyanide is used with one and a half times 

 as much sulphuric acid by volume. Hence the principal gain 

 in using the ordinary broken potassium cyanide of the trade and 

 a larger amount of sulphuric acid is prevention of waste; at the 

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