78 PROTECTION OF PLANTS — 1922-23 



White arsenic, particularly dust collector white arsenic or any low grade 

 white aisenic, if ground to sufBcient fineness, is superior to all finished arsenicals 

 and to pure or 99 per cent white arsenic for grasshopper and cut woim baits. 



3. In Bordeaux Mixture. 



In 1917, under instructions from the late Dr. Hewitt, we started investig- 

 ating the possibility of using white arsenic directly in Boideaux mixtuia. When 

 added directly to Bordeaux, white arsenic showed two serious defects. First 

 it would not wet readily. Second, a portion of it combined with the lime to form, 

 a very soluble arsenite of lime with the result that leaf injury was caused. Mr. 

 Kelsall was with me at the Annapolis Royal Laboratory at the time and as one 

 of us would give the problem up in disgust, the other would pick it up, add 

 something to it and then give it up again, until we finally got a fairly practical 

 method of using white arsenic in Bordeaux and a large number of farmers in 

 New Brunswick used it. 



The steps as I remember them, were as follows: — One of us by accident 

 mixed some dust collector arsenic with hydrated lime and found that it would 

 wet through quite readily and quickly. Next, one of us noticed that Bordeaux 

 into which we had mixed this white arsenic hydrated lime mixture was turning 

 color from a blue to a green on the leaves of the plants.. About this time we 

 were beginning to realize that copper sulphate was of very much more value 

 than lime in eliminating soluble arsenic. Then a long series of tests in the chem- 

 ical laboratory followed and Mr. Kelsall announced that a good factory pro- 

 duct could be made by our method, but that it was not yet fit for the use of 

 farmers. It was then dropped for almost a year and then we developed what 

 has proved a practical farm method. We prefer to use dust collector white 

 arsenic of around 90 to 95 percent purity on account of its greater solubility, 

 fineness and the speed with which it reacts. We mix equal parts of hydrated 

 lime and white arsenic together and mix them in the water into which we intend 

 to dissolve our copper sulphate. Then we hang a bag of copper sulphate in the 

 top of the water and let it dissolve, stirring occasionally. After the bluestone 

 dissolves, use in exactly the same manner as ordinary copper sulphate solution 

 in combining with lime to make a Bordeaux. Use about \}/2 lbs of dust collector 

 arsenic and \]A lbs of lime in the copper sulphate solution intended for an acre 

 of potatoes. 



The reaction that we suppose takes place is the formation of a veiy soluble 

 arsenite of lime by the hydrated lime and white arsenic loosely combining and 

 then as the copper sulphate dissolves the foimation of copper calcium arsenites 

 which give the green color to the solution and to the resultant Bordeaux. The 

 arsenite resulting from this procedure is very gelatinous, very adhesive, and an 

 excellent insecticide. We have found it absolutelv safe and effective. It is true 



