February, '19] WOGLUM: LIQUID HYDROCYANIC ACID 119 



contact with the tent top. This initial condition would point to the 

 top of the tent receiving maximum gas distribution sooner than the 

 bottom. Furthermore, the effect of the rise of gas would tend to 

 cause a greater concentration toward the top, although in a non-gas- 

 tight enclosure such as a tented tree, various factors, as yet little 

 understood, are constantly exerting important influences, changes in 

 which must alter the movement of the gas particles to no little extent. 

 The diffusion through the tenting is most important and unquestion- 

 ably is modified by such factors as texture, its condition as to moisture, 

 chemical treatment and accumulation of dirt particles. Furthermore, 

 atmospheric conditions during the exposure have been proven to 

 influence scale-kill, thus probably affecting tent leakage. Factors 

 acting wholly within the tent, yet believed to affect gas concentration 

 to some extent are absorption and adsorption of the foliage and the 

 physical condition of the soil. 



The violence of the reaction in an open generating vessel affects the 

 denseness and velocity of the rising column of hydrocyanic acid gas. 

 When the reaction is rapid the initial maximum gas concentration must 

 needs follow more quickly than when the generation takes place over a 

 protracted period. Furthermore, consideration of the fact that leak- 

 age occurs immediately on contact of the gas with the tent surface, 

 injects a factor that might alter the maximum gas density attained 

 between a slow or rapid generation. Such a view would signify a 

 difference, possibly very slight, in pot-generated gas from potassium 

 and sodium cyanid respectively, for solid potassium cyanid produces a 

 violent reaction practically complete within one to three minutes. 

 Solid sodium cyanid, on the other hand, is much slower in generation 

 and low grade material used in California to a limited extent several 

 years ago was observed in some cases to require fully fifteen minutes 

 for complete liberation of gas. 



The gas evolved from fumigating machines is in the form of a dense 

 cloud injected with much force at one edge of the tent along the ground. 

 The evolution of the gas is almost instantaneous and in a different 

 initial direction to that of pot generation. Thus the condition sur- 

 rounding the concentration and distribution of this gas, in differing 

 from that generated in vessels within the tented tree, gives grounds for 

 possible difference in results between the two methods. 



After this brief discussion of gas-distribution in pot and machine 

 practice, let us consider liquid hydrocyanic acid. This latter is in- 

 jected at the edge of the tent with a small amount of force, as a mist, 

 which on evaporating is left with little initial momentum. The result 

 is a gas somewhat distributed toward the bottom of the tent, having 

 much less initial velocity than in the case of gas generated under former 



