46 
beetles which had attacked the blossoms of tomato plants. By using 
white hellebore most excellent results were obtained. 
Professor Rolfs inquired concerning the effect of kainit upon the 
vines. Mr. Mally stated that as yet no reports had been made on this 
feature of the experiments. 
The following paper was then read: 
ON THE PREPARATION AND USE OF ARSENATE OF LEAD. 
By A. H. KirnKLAND, Malden, Mass. 
Since spraying with arsenate of lead has become an important measure 
in the control of certain injurious insects, a brief statement of the - 
methods followed in preparing this poison for use against the gypsy 
moth may be helpful to those who use large quantities of arsenical 
insecticides. 
In our spraying operations of the past summer we have used nearly 
3 tons of arsenate of lead mixture, made from the granulated white 
acetate of lead and from arsenate of soda of 50 per cent purity. The 
cost of these ingredients, from figures kindly furnished me by Messrs. 
William H. Swift & Co., manufacturing chemists, of Boston, Mass., are 
at present 74 cents per pound for acetate of lead, and 5 cents per pound 
for arsenate of soda. These figures, of course, are subject to more or 
less variation according to market conditions. To make 10 pounds of 
arsenate of lead, as used in our spraying operations in 150 gallons of 
water, there are required approximately 13 pounds 2+ ounces of acetate 
of lead and 5 pounds 7% ounces of arsenate of soda. In preparing this 
mixture it should be borne in mind that the relative amounts of these 
two salts must be governed by their purity, and that in all cases there 
should be a slight excess of the lead salt. 
As indicated by the writer in a paper read before the association at 
its last meeting, the best results are obtained by dissolving both salts 
separately and mixing the solutions in the spraying tank or in the 
supply tank where the latter is used. If the salts are mixed dry, the 
ordinary moisture of the air serves to bring about an incomplete reac- 
tion, and particles of the salts become coated with arsenate of lead and 
are transformed into minute, hard lumps, which clog the nozzles. Thus 
in order to gain the best results the necessary amounts of the two salts 
are placed in separate bags and the two bags tied together and labeled. 
To facilitate the work of weighing the salts, our chemist, Mr. F. J. 
Smith, makes use of two ballasts of the same weights as the required 
quantities of salts. By using these ballasts on balance scales two men 
can daily weigh, bag, and tie 1,000 pounds of the poison. For dissolv- 
ing the acetate of lead and arsenate of soda preparatory to spraying, the 
salts are placed in separate baskets and each basket is then suspended 
in a 10-gallon keg filled with water. From fifteen to twenty minutes 
are required for the dissolving of the salts. When this quantity has 
Dea ee See Loe eee ey 
