Distribution op HCN Gas in Greenhouse FuMiairiON 13 



house was 13.33 ^or No. 13, and 24.19 for No. 14. This shows 

 clearly that some factor besides the amount of cyanide used will 

 affect the concentration of gas obtained in the greenhouse, and 

 also will tend to explain the contradictory results often obtained 

 in scheduling greenhouses for fumigation. 



It seems that the larger the greenhouse the less rapid should 

 be the loss of gas through leakage and consequent diminu- 

 tion in killing strength. This is to be expected, since the volume 



/ £34-5 67 6 9 10 II 1213 1415 16 17 IQ 192021 2Z23Z4252627 282930. 



Fig. 6. Graph of Fumigation No. 6 



A, left bench; B, right bench; C, left collecting tube; D, 

 center collecting tube; E, comb collecting tube; F, right collect- 

 ing tube. 



of a solid increases as the cube of its diameter, while the surface 

 increases as the square. Thus the larger the greenhouse, the 

 less in proportion to its capacity is its surface, with consequently 

 less loss through leakage. No definite statement can be made 

 as to the correctness of this view, from the data collected. A 

 comparison of two fumigations made with the same relative 

 charge, ^-ounce per 1,000 cubic feet, in two different houses 

 shows a closely equivalent concentration at approximately equal 

 periods of time after the fumigation started. (See figures 7 and 

 9.) Judging from these results the balance is in favor of the 

 small house (No. 7), and this is increased if the results of the 

 fumigation charted on No. 5 are considered. In this case the 

 concentrations are uniformly higher than those of No. 7, which 



