TWENTY-FOURTH ANNUAL FRUIT-GROWERS' CONVENTION. 



95 



Arsenate of Lead has not been tried, except in a very limited way, for 

 the codling moth, but the highly satisfactory results obtained upon other 

 insects and the perfect safety to foliage would indicate that it might be 

 extremely profitable to experiment with. There are two methods of 

 making arsenate of lead, which produce substances somewhat different in 

 chemical structure, but about equally effective. In each method sixty- 

 eight per cent of arsenate of soda is used, and with this, in one case, 

 the ordinary white granular acetate of lead, and in the other, lead 

 nitrate.. The process of manufacture is as follows: The lead salt and 

 arsenate of soda are dissolved separately, and then poured into the 

 tank containing the water for spraying. The proportions used are 

 about as follows: For every ten ounces of arsenate of soda take twenty- 

 four ounces of lead acetate or twenty ounces of lead nitrate. These 

 substances can be purchased in the right proportions and tied up in 

 bags, so that it will take one bagful of each for each tank of water. 



The amounts given above are sufficient to make about a pound of the 

 pure arsenate of lead, which would probably be enough for one hundred 

 and fifty or two hundred gallons of water. It can be used with perfect 

 safety several times as strong as this. As a precautionary measure, it 

 might be well to* test the mixture in order to be sure that the arsenic is 

 all in combination, which can be done by the use of potassium bi- 

 chromate, which will produce a yellow precipitate if the solution 

 contains lead in excess, as it should. 



Arsenic and Lime. — Very satisfactory directions for making this 

 mixture are given in a letter from Professor Taft, of Michigan, one of 

 the first who extensively experimented with it. He writes: "I have 

 had excellent results from boiling one pound of (white) arsenic and two 

 pounds of lime in two gallons of water for forty minutes and then 

 ' diluting as required. When one pound of the arsenic prepared as 

 above is used in every three hundred to four hundred gallons of water, 

 I have found it equal to Paris green for destroying codling moth and 

 curculio, while one pound answers for one hundred and fifty to "two 

 hundred gallons of water when it is used upon potatoes; unless used in 

 Bordeaux mixture, I find it best to add a small amount of lime when 

 diluting. As the wholesale price of arsenic has averaged about seven 

 cents per pound for a number of years, while Paris green has whole- 

 saled at eighteen cents, it is evident that the latter is fully five times as 

 expensive." In reference to the comparative value of arsenic with soda 

 and lime, he further writes: "While some recommend the use of sal- 

 soda to dissolve the arsenic, we have not found it necessary; and as the 

 use cf soda at the rate commonly recommended nearly doubles the 

 expense of the spraying mixture, we have not recommended it, although 

 the claim that when sal-soda is used it is possible to tell when the 

 arsenic is dissolved, is correct." The only trouble with this mixture 



