188 



For many years the application of Paris giecn (arsenilo of copper, insoluble) 

 iias been in use for the destruction of the Colorado potato beetle. If the copper of 

 such became and remained easily soluble, thousands of acres would long ere this 

 have been rendered barren. 



To sura up, my contention is that the copper which reaches the ground from 

 properly conducted S})vaying i3 so minute in quantity and so insoluble in nature that 

 no fear need be entertained of injury to growing vegetation. It certainly seems to 

 me that it would be very foolish to relinquish so patent a means of preserving our 

 orchards and vineyards and their fruit, before science and practice proclaimed the 

 true nature of such to be a curse rather than a blessing. 



THE APPLICATION OF PARIS GEEEN IN SOAP SOLUTION AS AN 



INSECTICIDE. 



The question has arisen whether the toxic action of Paris green as an insecticide 

 is to any extent weakened or destroyed when this poison is applied with soap solu- 

 tion. For the purpose of answering this problem, I have carried out a number of 

 laboratory experiments, the results of which form the basis of the present report. 



Paris green (aceto-arsenite of copper) is an emerald green salt which is practi- 

 cally insoluble in water. The first experiment consisted in shaking up Paris green 

 with water constantly for more than a week. The Paris green was then filtered off. 

 Not a trace of arsenic could be detected in the filtrate, though the most delicate 

 chemical process was emploj^ed. 



Strong ammonia readily and completely dissolves Paris green, forming a deep 

 blue solution and capable of being diluted with water, without decomposition or pre- 

 cipita'ion. 



The fixed alkalies — potash and soda — in strong aqueous solution decompose this 

 poison, the blue hydrate of copper separating. This on heating first becomes changed 

 into the black oxide, and finally the red cuprous oxide, the arsenic going into the 

 solution as potassium arsenite. 



A number of experiments were then tried as to the solvent action of different 

 soap solutions on this insecticide. The soaps used were (1) whale oil soap, (2) com- 

 mon brown soap, (3) " English " soft soap. 



The whale oil soap, strength 1 lb. to 8 gallons, was not alkaline to test paper. 

 The Paris green was shaken up with this solution repeatedly for five days and the 

 mixture then filtered. Not a trace of arsenic could be detected in the filtrate, show- 

 ing that no decomposition of the Paris green had taken place. The latter retained 

 its bright green appearance throughout the experiment. 



The solutions of the "common brown soap" and the "English" soft soap were 

 not of any stated strength, but were made as strong as it was possible to make them. 

 By this means a severe and extreme test was made in each case. 



The common biown soap was strongly alkaline. This solution after acting upon 

 it for five days was found to slightly decompose the Paris green, arsenic being 

 detected in the filtrate. The reoidual Paris green was, however, bright green, 

 which together with the fact that but traces of arsenic passed into solution, shows 

 that only to a very slight degree had the poison been acted upon. 



With the "English" soft soap solution, which was much more strongly alkar 

 line than the preceding, there was more decomposition, i.e. more arsenic passed 

 into solution and more copper precipitated than in the experiment just cited. The 

 treatment was similar as in the previous trials, and the result showed that heavy 

 traces of arsenic had passe I into solution, while at the same time a slight brown 

 deposit of oxide of copper was to be noticed on the residual Paris green. 



If it were necessary for the eflScacy of the poison that the Paris green be applied 

 in such liquids as would have no decomposing or solvent action upon it, the results 

 of these experiments show that no pi-actical harm or deterioration would result from 

 using it with soap solution. When it is remembered, however, that Paris green, al- 

 though insoluble in water, passes more or less rapidly into solution by the action of 



