240 Peach-Growing 



The dosage that has been found most satisfactory Is as 

 follows : 



For 100 cubic feet of space — 



Potassium cyanide, 1 ounce (by weight). 

 Sulfuric acid, 1 ounce (fluid). 

 Water, 3 ounces (fluid). 



The trees are placed in the fumigating box or room, the 

 proper quantities of the materials are measured out very 

 accurately in accordance with the size of the box or room, 

 and then combined by first placing the water in a suitable 

 container, then adding the sulfuric acid, and finally the 

 potassium cyanide. The best container in which to generate 

 the gas is an earthenware vessel having a capacity consider- 

 ably greater than the combined quantities of the materials 

 used. The trees should be treated for at least forty minutes. 



On account of recent difficulties in obtaining potassium 

 cyanide, sodium cyanide has been used to some extent in 

 its place for fumigating nursery stock and with equally good 

 results. The pure chemical yields considerably more gas 

 to a given weight than the same weight of a pure potassium 

 cyanide. The purity of the former is expressed in terms of 

 the latter. Hence, a grade of sodium cyanide designated 

 as 126 to 130 per cent pure is equivalent to a grade of po- 

 tassium cyanide of 98 to 99 per cent purity. Therefore, 

 in using sodium cyanide, about one-fourth less by weight is 

 needed for a given unit of space. The proportion of chem- 

 icals advised when this substitution is used is : 



For 125 cubic feet of space — 



Sodium cyanide, 1 ounce (by weight). 

 Sulfuric acid, 1^ ounces (fluid). 

 Water, 2 ounces (fluid). 



