20 MISSOURI AGRICULTURAL EXPERIMENT STATION BULLETIN 177 



The bin or building should be allowed to fumigate for from 36 to 48 

 hours. 



For fumigating seeds with carbon bisulphide, from 1 to iy 2 pounds 

 should be used to every 1000 cubic feet. 



Carbon bisulphide has been tried a number of times upon nursery stock 

 for destroying scale insects, but up to the present time has proven unsatis- 

 factory. 



Chemical composition of carbon bisulphide. According to W. E. Hinds, 

 of the United State sDepartment of Agriculture, Farmers' Bulletin 145, "the 

 chemical symbol of carbon bisulphide is CS 2 . Its molecules consist of one 

 atom of carbon united with two atoms of sulphur. The specific gravity of 

 the liquid is 1.29. The vapor is 2.63 times as heavy as atmospheric air. The 

 pure article volatilizes rapidly and completely when exposed to the air. The 

 liquid boils at 115F. 



"The vapor takes fire in air at about 300 F. and burns with a faint blue 

 flame, scarcely visible in daylight, but evolving considerable heat and de- 

 composing the carbon bisulphide into carbon dioxide (CO 2 ) and sulphur 

 dioxide (SO 2 ). The latter is the familiar gas given off by the burning of 

 sulphur matches and is a strongly poisonous suffocating gas, which should 

 not be inhaled. Carbon bisulphide vapor mixed with three times its volume 

 of oxygen, or an amount of air containing that amount of oxygen, forms a 

 mixture which is very highly explosive upon ignition. As 21 per cent of the 

 air is oxygen, one volume of liquid carbon bisulphide evaporated in 5,357 

 volumes of air would form such a mixture. An atmosphere composed of 

 one volume of carbon bisulphide vapor to approximately 14.3 volumes of 

 air is liable to violent explosion in the presence of fire of any kind whatever, 

 or a temperature of about 300 F. without flame. This is about the maxi- 

 mum danger point from explosion in the use of carbon bisulphide." 



The higher the temperature, the more carbon bisulphide will be taken 

 up by the air. 



RESULTS OF EXPERIMENTS WITH CARBON BISULPHIDE 



As has already been pointed out, carbon bisulphide is probably the most 

 generally used insecticide for fumigating, especially for such insects as 

 grain weevil. It has been tried to some extent upon nursery stock for the 

 -control of San Jose scale, but so far satisfactory results have not been re- 

 ported. Carbon bisulphide is cheaper than hydrocyanic-acid gas, easier to 

 handle and, used as a poison,, does not act in an effective way so quickly 

 Avhich makes it less dangerous for the person handling it. 



Object. The idea in using carbon bisulphide was to determine if possi- 

 ble, whether or not it could be used at 'all for destroying San Jose scale 

 upon live plants without injury to the plants. Owing to its cheapness and 

 the ease with which it can be used as compared with hydrocyanic-acid gas, 

 carbon bisulphide would be a great deal more desirable provided the same 

 results could be obtained. 



Procedure. The same fumigating box was used with the carbon bisul- 



