50 GARDEN FOES. 



slum cyanide is only made in the one strength, so that 

 when the grower sees the results of experiments pub- 

 lished in which so much sodium cyanide was used without 

 hurting the plants operated upon, he need not hesitate to 

 use the same weight of chemical; but if he sees that 

 potassium cyanide was used he must first find out what 

 strength was used before repeating the operation for him- 

 self. All he must remember is that sodium cyanide 130 

 per cent, is the same thing as sodium-potassium cyanide 

 98 to .100 per cent, purity. It is a pity that the fonner term 

 was ever allowed to exist at all. It is absurd and inaccu- 

 rate, and should never have been allowed to pass by the 

 introducer of it as a horticultural chemical. It is true 

 he explains the incongruity of the term 130 per cent., but 

 he does not say that it is a double salt of sodium and 

 potassium. 



" How it is Done — To come to the actual operation 

 of cyaniding, first estimate the space in cubic feet to be 

 operated upon. Then to every 2,000 cubic feet allow for 

 a first experimental application |oz. of 98 i:>er cent, 

 sodium - potassium cyanide, and 1 J fluid ounces of 

 sulphuric acid 1.8 per cent, specific gravity. The 

 acid, before using, must be diluted by pouring it 

 slowly into two and a half times its bulk of cold 

 water. For a small greenhouse of, say, 4,000 cubic feet, 

 where only two sets of apparatus w^ould be required, pro- 

 ceedings may bo taken as follows: Obtain two glazed 

 eai-thenware pans. Into these put the diluted sul])huric 

 acid. Above the pans hang a piece of board, which can 

 be swung to and fro like a punkah by means of a string- 

 pulled from outside. Wrap the dose of cyanide in a ^mall 

 piece of llotting-paper or muslin, and, if possible, suspend 

 it just over the pan by a cotton, which can be cut from 

 outside. If this cannot be done, the packet must be 

 dropped into the acid by hand, and a rapid retreat be 

 made at once. Do not use much wrapping for the cyanide, 

 or it may float on the acid, and no action take place for 



