February, '19] WOGLUM: liquid HYDROCYANIC ACID 123 



hydrocyanic acid were carried on at comparatively high temperatures. 

 Fumigation at very low temperatures would tend to develop even 

 greater differences in scale-kill at various distances from the ground. 



This greater density of gas toward the bottom of the tent with cor- 

 responding increased efficiency will necessitate changes in the present 

 dosage schedule based on pot generation. A dosage schedule for 

 Uquid hydrocyanic acid is now being prepared and will be ready for 

 the coming season's work. 



The question naturally arises, in view of the difference in distribu- 

 tion between gas from liquid hydrocyanic acid and the other methods 

 of generation, as to any advantage or disadvantage therefrom in the 

 use of this recent introduction. The infestation of scale insects on 

 large citrus fruit trees is usually most severe on the lower or most 

 protected part of the tree; especially is this true of the purple scale. 

 The greater killing effect of liquid hydrocyanic acid at that part of the 

 tree most severely infested with scale is the ideal to be sought, and at 

 once brings this gas into favor over the field-generated product for 

 citrus tree fumigation. 



There are other advantages favoring liquid hydrocyanic acid, which 

 in themselves indicate that this new method will displace all others. 

 The expenses of an outfit are reduced by doing away with cumbersome 

 apparatus such as pots, generating machines, sulphuric acid drums and 

 boxes of cyanid. The cost of tent mending is almost entirely done 

 away with as liquid hydrocyanic acid is harmless to cloth. The treat- 

 ment of small trees, frequently with such poor results in the past, can 

 be performed with greater accuracy and corresponding certainty of 

 results. Greater speed in tree treatment can be attained than pre- 

 viously and it appears possible that the quantity of hydrocyanic acid 

 required for scale-kill can be slightly reduced over that formerly 

 required. 



However, improvement in manufacture so as to furnish a uniformly 

 high grade product free of impurities that might start decomposition, 

 improvements in containers through the use of a material free from 

 chemical action with the gas, and improvement in the field application 

 to guarantee accurate delivery and complete gasification of the re- 

 quired charge are necessary before this gas is placed on the high plane 

 demanded for orchard fumigation in California. Assurance has been 

 given that these faults will be corrected in the immediate future, in 

 which case by the end of another year the hundred outfits using this 

 gas are certain to be greatly augmented for time to come, or at least 

 until some scientist discovers a method of scale control its superior. 



{End of proceedings, to be continued.) 



