SECTION II. ORGANIC POISONS 



Carbon Disulphide. This poisonous substance is manu- 

 factured by passing sulphur vapour over red-hot charcoal. 

 Carbon disulphide is a heavy liquid giving a heavy vapour and 

 can be used to destroy weevils in corn. A small depression is 

 made at the apex of a heap of corn and the carbon disulphide 

 poured in ; the heavy vapour sinks to the bottom of the 

 heap. The liquid may also be used to pour down the burrows 

 of foxes, rabbits, etc. ; it has been employed to destroy 

 wire-worms and other grubs in the soil. In its action carbon 

 disulphide is at first anaesthetic ; insects often recover 

 momentarily from its influence, and crawl about, but collapse 

 finally in a few minutes. It is much more powerful as a 

 poison for insects than naphthalene, but not so strong as 

 carbon tetra-chloride. 



ThiocarbonatesandPerthiocarbonates. Whencarbon 

 disulphide is agitated with sodium sulphide, a thiocarbonate 

 is formed, Na 2 CS 3 , but if free sulphur is also present the 

 reaction occurs more rapidly and the compound, Na 2 CS 4 , 

 sodium perthiocarbonate is formed. In presence of carbonic 

 acid these substances give off carbon disulphide, hydrogen 

 sulphide, and in the latter case sulphur as well. A crude 

 mixture containing thiocarbonate, perthiocarbonate and 

 sulphide has been used for spraying vines and potatoes. 



Formalin. This powerful antiseptic is a 40 % solution 

 of formaldehyde in water. It is made by passing air under 

 pressure through a " carburetter " supplied with methyl 

 alcohol. The methyl alcohol need not be more concentrated 

 than 90 %, but the temperature must be raised to about 

 45-50 C. (110-120 F.) to obtain a high enough proportion 

 of alcohol vapour. The air and alcohol vapour pass through 

 a catalyzer consisting of copper gauze at a low red heat. 

 Heat is necessary to start the reaction, but the heat evolved 



