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BULLETIN 1147, U. S. DEPARTMENT OF AGRICULTURE. 



The amount of arsenic made soluble was much larger when acid 

 lead arsenate was combined with kerosene emulsion than when cal- 

 cium arsenate was combined with it. The same amount of arsenic 

 was rendered soluble in one day as in three days in the case of the 

 acid lead arsenate. When calcium arsenate was used, 1.5 per cent 

 more of the total arsenic was made soluble the third day than the 

 first day. It is evident that the lead and the lime of the arsenates 

 combined with the fatty acids to produce soaps, leaving the corre- 

 sponding amounts of arsenic in a soluble condition. The results show 

 that less decomposition occurred in the case of calcium arsenate 

 mixed with kerosene emulsion than in the case of acid lead arsenate 

 and kerosene emulsion. Both mixtures are chemically incompatible. 



ARSENATES AND FISH-OIL SOAP. 



Combinations of acid lead arsenate with fish-oil soap are sometimes 

 made. Because of the large quantity of calcium arsenate now being 

 manufactured, it seemed advisable to test combinations of calcium 

 arsenate and of acid lead arsenate with fish-oil soap in order to deter- 

 mine how much arsenic might be made soluble. 



Fish-oil soap solutions of two strengths, 1 and 2 pounds of soap 

 per 50 gallons, were prepared. The fish-oil soap was the same kind 

 as that used in making the kerosene emulsion. A series of 300 cubic 

 centimeter flasks were filled with the soap solution. No arsenical 

 was added to some of the flasks which were used as controls, but 0.8 

 gram of acid lead arsenate (sample 39) or 0.667 gram of calcium 

 arsenate (sample 57) was added to the others. A one-day period 

 was taken for agitating the solutions, because the results with kero- 

 sene emulsion snowed that in one day the reactions were practically 

 complete for the lead arsenate and much retarded in the case of the 

 calcium arsenate. 



Table 8. — Arsenic rendered soluble on combining lead or calcium arsenates with fish-oil 



soap. 



Sample 

 No. 



Material analyzed. 



Arsenic 



(As)present 



in sample 



taken. 



Arsenic (As) rendered 

 soluble after standing 

 for 1 day. 



57 





Grams. 

 0. 1753 

 .1717 

 .1753 

 .1717 

 .1753 

 .1717 



Grams. 

 0.0003 

 .0032 

 .0503 

 .H75 

 .0667 

 .1703 



Per tent. 

 0.17 



39 





1.86 





Calcium arsenate plus fish-oil soap (1 pound to 50 gallons). 

 Acid lead arsenate plus fish-oil soap ( 1 pound to 50 gallons) . . 

 Calcium arsenate plus fish-oil soap (2 pounds to 50 gallons) . . 

 Acid lead arsenate plus fish-oil soap (2 pounds to 50 gallons) . 



28.69 

 85.90 

 38.05 

 99.18 



1 Calcium arsenate at the rate of 0.93 pound per 50 gallons. 



2 Lead arsenate at the rate of 1.11 pounds per 50 gallons. 



The results obtained (Table 8) follow the trend of the results 

 secured with kerosene emulsion (Table 7) in that they show that 

 more arsenic was rendered soluble when acid lead arsenate was used 

 than when calcium arsenate was used. They also show that the 

 greater the quantity of fish-oil soap used the larger the amount of 

 soluble arsenic formed. All of the arsenic was made soluble when 

 acid lead arsenate was mixed with the soap at the rate of 2 pounds 

 per 50 gallons. The lead soaps are more readily formed than the 



