16 N. J. Agricultural Experiment Stations, Bulletin 355 



higher, with a difference of 20 per cent, relative humidity. Like- 

 wise, the results of a comparison of two tests made in the same 

 greenhouse, having a capacity of 3,341 cubic feet, and with the 

 same charge, but with rather a large temperature difference (60°- 

 71 °F.) and with a difference in relative humidity of 21 per cent, 

 showed a greater concentration of HCN at the higher humidity 

 and the lower temperature. 



z 



8 iO /2 /4 /6 /6 20 ZZ 24 26 28 30 32 



Hoi — \oV 



,A a 



HOUSE 



PLAN 



CAPACITY 

 4.866 cu.ft 



Fig. 9. Graph of Fumigation No. 9 



A, left bench; B, center bench; C, right bench; D, left col- 

 lecting tube; E, center collecting tube; F, right collecting tube; 

 G, comb coHecting tube. 



Determination of Minimum Dosage for Plant Lice 



In order to correlate the findings in regard to concentration 

 of HCN gas in the greenhouse with the actual dosage necessary 

 to kill aphis, a series of experiments was carried out to test for 

 minimum dosage, in relation to temperature and moisture. 



Glass flasks, Avith a capacity of i liter, were used in which 

 to liberate the gas. The correct amount of HCN gas was 

 formed in each by diluting a 95.3 per cent solution of liquid 

 HCN with water, so that one drop of water would contain in 

 solution a definite quantity of HCN. By evaporating this drop 

 in the flask by the aid of gentle heat, an atmosphere of HCN of 

 the desired concentration was produced in the flask. The 

 aphids were placed in small glass tubes about 2 inches long 

 and 3/8 inch in internal diameter. Cheesecloth was fastened 



