le lain = 
103 
the acetate, the saving made where several tons are to be prepared is 
quite an item. 
At the time when the diplumbic arsenate was first brought to the 
attention of this Association only a few experiments had been made. 
Since that date the insecticide has been tested in an extensive series 
of laboratory and field experiments, and in 1898 and again the present 
year in actual spraying operations in the field. A part of the results 
of the experiments have been published in the report of the gipsy- 
moth committee, January, 1898, and without presenting the mass of 
details from the numerous tests we may state in brief that in every 
case the arsenate of lead made from the nitrate has proven itself equal 
if not superior to that prepared from the acetate. 
In preparing arsenate of lead by either process it has been found most 
economical to use a high grade of arsenate of soda, as the impurities, 
such as salt, in the lower grades neutralize a considerable part of the 
soluble lead before the reaction with the arsenate of soda can com- 
mence. The gipsy-moth committee obtained from a firm in England 
an arsenate of soda that showed on analysis 67.5 per cent of arsenic. 
This material costs when delivered $0.052 per pound. To make 1 ton 
of arsenate of lead there are required 888 pounds of this arsenate of 
soda at a cost of $46.18, and 2,398 pounds nitrate of lead at a cost of 
$161.87, the total cost being $208.05. With the same grade of arsenate 
of soda but using acetate of lead there are required for 1 ton of arsenate 
of lead 758 pounds arsenate of soda, costing $39.42, and 2,593.8 pounds 
acetate of lead, costing $207.50, a total cost for ingredients of $246.92. 
At the current prices of the ingredients this leaves a balance of $38.87 
per ton in favor of the arsenate of lead made from the nitrate. 
Where the proportionate amounts of arsenate of soda and acetate of 
lead are tied in packages in the ordinary procedure, the dampness of 
the acetate of lead will set up a partial reaction, and thus a part of the 
value of the insecticide is lost. When nitrate of lead is used there is 
but little of this partial reaction. ; 
Mr. Saunders inquired as to the strength of the mixture of arsenate 
of lead used against the gipsy moth. 
Mr. Kirkland stated that in this work the proportion was 125 pounds 
to 150 gallons of water; but that from 3 to 4 pounds to 150 gallons was 
ample to destroy the tent caterpillar, tussock moth, and other common 
larve. 
Mr. Marlatt expressed the opinion that if the total expenditure in 
the work against the gypsy moth had yielded no other results than the 
discovery of arsenate of lead and the invention of the improved 
spraying machinery, the money would have been well invested. 
Arsenate of lead was a safe insecticide to use and one of the most 
valuable results of the gypsy-moth work. 
