NOTES ON RECENT RESEARCH. 



249 



Carbon Bisulphide Insecticides. 



Insecticide, Carbon Bisulphide as an. By W. E. Hinds 

 (U.S.A. Dept. Agr., Far. Bull. No. 145; pp. 1-28; 1902).— This paper 

 gives the principal facts concerning the use and effect of carbon bisul- 

 phide, together with an historical account of its uses in economic zoology. 

 The chemical side of the subject is treated of in an appendix setting forth 

 the properties and behaviour of the liquid under various conditions. 



Carbon bisulphide is a colourless watery liquid formed by the union 

 of two elementary particles of sulphur with one of carbon (charcoal). 

 Its chemical symbol is CS 2 . It is made on a large scale by passing the 

 fumes of burning sulphur over red-hot charcoal. The resulting vapours 

 are condensed to a liquid form by cooling, and the impurities are re- 

 moved therefrom. It is very volatile. The rapidity of evaporation 

 depends mainly upon the area of the evaporating surface and the 

 temperature of the liquid and the air. When perfectly pure the liquid 

 has an acrid taste, with an odour somewhat resembling ether or chloro- 

 form. The ordinary commercial article has, however, a rank foetid odour 

 that is extremely offensive, and is liable to stain articles treated with it. 

 The vapour is 2'63 times as heavy as the air, and although it diffuses 

 quite rapidly it tends to work downwards more strongly than upwards ; it 

 would therefore be more dense at the lower levels. Both the vapour and 

 the solution are powerful disinfectants, and meats are said to keep in an 

 atmosphere of it for months. The liquid boils at a temperature of 115° F. 



Effects of Inhalation of the Vapour. 



The gas is highly poisonous, producing giddiness, vomiting, conges- 

 tion, coma, and finally death. These, of course, are its extreme effects. 

 The operator should not, however, enter a room which is heavily charged 

 with the vapour. 



Carbon bisulphide is applicable only where the vapour can be more or 

 less confined, and is used chiefly for root-feeding insects, and for insects 

 affecting stored grain and wearing apparel. For use against the 

 Phylloxera and other root-feeding insects the following information is 

 given: — 



Diffusion of the Vapour in the Soil. — Upon being introduced into the 

 soil at some depth below the surface the liquid evaporates as it does in 

 the open air, only much more slowly. The vapour tends to diffuse 

 through all the air spaces of the soil. It thus produces an atmosphere 

 which is fatal to all insects living within its reach. The rapidity of 

 evaporation, the extent of diffusion, and the persistence of the vapour in 

 the soil vary widely in soils of varying characters and conditions, so no 

 one rule of application can be employed in all cases, and it thus becomes 

 necessary to understand the influence of various factors that proper 

 allowance may be made for them and the destruction of the insects 

 attained without injuring the plants. 



Moisture. — Carbon bisulphide evaporates most rapidly in a warm, dry, 

 sandy soil, and the persistence of the vapour is also shortest in such soil. 

 In fact it diffuses so rapidly that most insects will survive an ordinary 

 dose ; and if the dose is increased so as to kill the insects, it is likely to 



