110 Maine Agricultural Experiment Station. 1918. 



pare the orthoarsenate according to the methods recommended 

 by certain other writers. What they obtained, as shown by 

 analysis, did not correspond to a pure orthoarsenate of lead, 

 since it contained more lead and less arsenic than the theoretical 

 figures. Their tests led them to conclude that what they ob- 

 tained was a distinctly different chemical compound, a new 

 basic lead arsenate of which there was no previous mention in 

 the literature. Furthermore, to quote farther, they state, p. 9: 

 "Without going into any lengthy discussion of the reactions 

 used, the authors will state that lead orthoarsenate is not formed 

 under the ordinary aqueous conditions employed in the manu- 

 facture of commercial lead arsenate, and that it is not a com- 

 ponent of the commercial material as has been formerly sup- 

 posed. The compound present, which has been represented to 

 be the orthoarsenate, is in reality the basic lead arsenic men- 

 tioned above." In a letter to the writer, under date of Febru- 

 ary 12, 1917, one of the authors (R) just quoted, stated that 

 there are now on the market two brands of arsenate of lead 

 which their analyses show to be of a neutral type and mentioned 

 another which the manufacturers claim to be a neutral arsenate 

 of lead. 



Orthoarsenate of lead has been recommended as a safer 

 material for use with lime-sulphur on peaches and has also been 

 advocated for apple spraying. In view of the evidence cited 

 above it would not be strange if some confusion should exist 

 in the minds of those who are conducting spraying experiments 

 as to what form of arsenate of lead they were using. In fact 

 letters from 3 different horticulturists to the writer, two from 

 Canada and one from another state, specifically stated that a 

 certain brand put out by one concern is a neutral of orthoar- 

 senate of lead. The chemists of this Station examined two 

 samples of this brand in 19 14 and 3 samples in 191 5. taken in 

 the open market in Maine. The arsenic content of these sam- 

 ples was such that they could have been by no possibility a 

 neutral arsenate. The analyses do indicate that they were, in 

 reality, fairly pure and consequently high grade acid arsenates. 

 It is significant to note that the records indicate that the word 

 "neutral" appeared on the label in 19 14 and not in 191 5. More- 

 over when asked in the winter of 191 7 if they could furnish us 

 with another form for experimental work this firm replied that 



