432 JOURNAL OF ECONOMIC ENTOMOLOGY [Vol. 12 



igniting C.P. calcium carbonate until all carbon dioxide was driven off; 

 lime sulfur was made from recrystallized sulfur and from lime obtained 

 as described above; lead hydrogen arsenate was prepared by the 

 method outHned by Robinson and Tartar.^ The commercial products 

 us^ed were standard brands found on the market. 



The outHne of procedure was as follows: The hme sulfur, both 

 laborator}^ prepared sample and commercial brands was brought to a 

 density of 1.262 or 30 degrees Baume and diluted 1 part to 40 parts 

 of water or summer strength. After slaking with a small amount of 

 water, lime was added at the rate of 10 pounds to 100 gallons. Fi- 

 nally, lead hydrogen arsenate was added at the rate of 2 pounds to 100 

 gallons or 4.8 grams to 1000 cc, the quantity used in the experiment. 

 In this manner, triplicate portions of each brand of lime sulfur taken 

 were prepared. The mixtures were then shaken occasionally during 

 three hours and after filtration, determinations for soluble arsenic were 

 made. Table III gives the per cent of arsenic found: 



' Table III. Per cent op Soluble Arsenic in Lime Sulfur Solution from Combination Spray, 



Treated and Untreated with Lime 



Lab. prepared lime sulfur and lead arsenate 



Commercial sample No. 1, lime sulfur and lead arsenate 

 Commercial sample No. 2, lime sulfur and lead arsenate 



Without lime With lime 



12.90% 

 12.20% 

 12.90% 



It is ol)vious from these results that the presence of free lime prevents 

 arsenic from going into solution as a soluble salt. On the other hand 

 where no lime was added a usual high per cent of soluble arsenic was 

 found indicating that over 12 per cent of the lead hydrogen arsenate 

 was decomposed, decreasing its efficiency accordingly. Observation 

 on the changes that occurred during the reaction showed that those 

 samples treated with hme slowly turned to a gray color similar to the 

 basic lead arsenate and hme sulfur mixture where the amount of 

 chemical changes was neghgible, while those untreated immediately 

 turned black, indicating the breaking down of both hme sulfur and 

 lead arsenate and the formation of lead sulfid. 



Change in the polysulfid content of the hme sulfur was likewise 

 studied. The total sulfid content was first determined in the diluted 

 lime sulfur solution, and, after treatment as described above, again 

 determined after shaking at intervals during three hours and again 

 after two days. The table gives the grams contained in 1000 cc. of 

 lime sulfur and lead arsenate mixture. 



1 Robinson, R. H., and Tartar, H. V. The Arsenates of Lead, Ore. Exp. Sta. Bui. 

 128, 1915. 



