Apple Spraying Experiments in 1916 and 1917. Ill 



they could supply us only with what they claimed to be, and the 

 Station's analysis showed to be, a very high grade acid arsenate. 



Composition of Materials Used in 1917. 



Through the cooperation of the Chemical Department of 

 this Station analyses were made of certain materials, particu- 

 larly the arsenicals used in the 191 7 experiments. The dry 

 arsenate of lead furnished by the Corona Chemical Company 

 and the Sherwin-Williams Company showed a chemical composi- 

 tion of very closely the right proportions to conform to and 

 but slightly lower in As 2 5 and PbO than is the theoretical 

 requirement for pure acid arsenate of lead. 



The "T. P." arsenate of lead obtained from the Thomsen 

 Chemical Company was in a paste form but since this discus- 

 sion is concerned entirely with the type of the arsenate of lead 

 used in the experiments the material, for convenience in making 

 comparisons, was reduced to nearly a water-free basis before 

 the analysis was made. The moisture content of the final or 

 dry sample used was 0.22 per cent. On this basis 22.43 P er 

 cent As 2 O s and 74.01 per cent PbO were found, the ratio being 

 1 :3-299. Robinson and Tartar* point out that the theoretical 

 ratio between As 2 O s and PbO in an acid arsenate is 1 : 1.945 

 and in a neutral arsenate is 1 12.91 1. In their attempts to pre- 

 pare a neutral or orthoarsenate of lead, an analysis of the sam- 

 ples obtained gave a ratio between the two compounds men- 

 tioned varying from 1 13 180 to 1 :3-i96. As has already been 

 stated they expressed the opinion that arsenate of this com- 

 position is a basic and not an orthoarsenate. It will be noted 

 that the ratio given by the analysis of the "T. P." arsenate shows 

 even a greater deviation from the theoretical composition of an 

 orthoarsenate. f 



*/. c. p. 9. 



fNo attempt has been made to look up the analyses of this brand of 

 arsenate of lead which have been made by the inspection service main- 

 tained by different states but one analysis of a sample in 1917 has come 

 to the writer's attention. This is reported on p. 9 of Bulletin 315 of 

 the New Jersey Agricultural Experiment Station. A sample of "Or- 

 chard Brand Powdered Arsenate of Lead — T. P." is reported as carry- 

 ing 24.26 per cent of arsenic oxide and 71.72 per cent lead oxide. The 

 ratio here corresponds fairly closely to the theoretical for a neutral or 

 orthoarsenate. 



