324 CONNECTICUT EXPERIMENT STATION REPORT, 1907—1908. 



and the lead oxide from 25.59 to 44.05 per cent. The soluble 

 arsenic oxide was low in all cases, ranging from 0.22 to 1.3 1 per 

 cent., and this after a treatment for ten days. No soluble lead 

 oxide was found in any of the samples. The nature of the impuri- 

 ties was not determined in any case; 19210, 19358, 19643 and 

 19357, however, showed traces of nitrates. The impurities were 

 not high except in three samples, 19211, 19643 and 19358; neither 

 Disparene nor Aiboneta was sold as pure lead arsenate and there- 

 fore cannot be considered adulterated; the Monmouth sample, 

 however, was sold as a pure material; in addition to its high 

 content of impurities, it also contains the lowest percentages of 

 both arsenic and lead oxides. 



Lead arsenate is usually prepared by the action of lead acetate 

 on disodium arsenate; some manufacturers, however, substitute 

 lead nitrate for the acetate. Smith* has shown that the com- 

 mercial grades of sodium arsenate and lead acetate and nitrate 

 vary considerably. He foimd the lead oxide in lead acetate varied 

 from 58.81 to 66.80 per cent., and in lead nitrate from 66.37 to 

 68.37 P^*" cent. ; while in sodium arsenate the arsenic oxide varied 

 from 36.77 to 47.80 per cent. The calculation of the theoretical 

 composition of commercial lead arsenate is, therefore, attended 

 with some difficulty. Haywood,! however, has shown that, with 

 pure chemicals, where lead acetate is used the theoretical com- 

 position should be 7440 per cent, lead oxide and 25.60 per cent, 

 arsenic oxide; and where lead nitrate is used, 64.26 and 33.15 

 per cent., respectively. The methods used in the above analyses 

 give results very close to theory where the lead arsenate is pre- 

 pared from lead nitrate, but where lead acetate is used slightly 

 higher than theory for arsenic oxide and slightly lower for lead 

 oxide, indicating that probably some secondary reaction takes 

 place during the process of manufacture, resulting in the forma- 

 tion of some compound other than lead arsenate, probably an 

 acid lead arsenate. By referring to the analyses of the samples 

 on the water-free basis, it appears that 18703, 19209, 19210, 

 19213 and 19643 are made from lead nitrate, the others from 

 lead acetate. Formerly it was the practice to add glucose to 

 increase the adhesive power of the arsenate, but it has been 

 shown that it adheres almost as well without glucose as with it, 

 and its use has been largely discontinued. 



* Agr. Massachusetts, 1897, 357-369. . 



t U. S. Dept. of Agr., Bur. of Chem., Bull. 105, 16S. 



