6 LEAD ARSENATE. 



Many of these very cheerfully gave the information asked for, but 

 several refused, and a few others did not have the data available. 

 Judging from the information which has been obtained, the total 

 amount sold in 1908 was approximately 2,500 tons, the value of which 

 was more than half a million dollars. In addition, a great quantity 

 of the home-made material has been used, but this quantity can not 

 be estimated. 



It was on account of the great importance which lead arsenate is 

 assuming for spraying purposes and in view of certain variable results 

 which have been reported, that this study was begun by the Bureau 

 of Chemistry two years ago, principally for the purpose of determin- 

 ing, if possible, the conditions which cause it to be injurious to foliage 

 in some cases. The experiments have been conducted for two suc- 

 cessive years, as it was considered impossible to arrive at any trust- 

 worthy conclusions in a shorter period. At the same time a study of 

 the composition of the lead arsenates found on the market and also 

 that of ''home-made" lead arsenate was made, including analyses of 

 such of the chemicals entering into its manufacture as could be pro- 

 cured from druggists and other sources. 



This work, therefore, has been divided into three parts, as follows: 



I. Composition of lead arsenates found on the market. II. "Home- 

 made" lead arsenate, and the chemicals entering into its manufacture. 

 III. Action of lead arsenate on foliage. 



The work has been carried out in cooperation with the Bureau of 

 Entomology, Mr. A. L. Quaintance, in charge of deciduous-fruit 

 insect investigations, having furnished the larger number of the sam- 

 ples herein reported and cooperated in the carrying out of the spraying 

 experiments outlined in the third section. 



I. COMPOSITION OF LEAD ARSENATES FOUND ON THE MAftKET. 

 SCOPE OF THE INVESTIGATION. 



The object of this investigation was to determine by chemical 

 analysis the quality or grade of the leading lead arsenates as found 

 on the open market and supplied to the trade. To this end samples 

 were obtained at many points in different sections of the United 

 States by various collectors, and, while the products of a few manu- 

 facturers are not represented, all of the leading brands, representing 

 about 98 per cent of the total output, are included in the list. In a 

 number of instances several samples of the same brand, purchased 

 at different times and places, have been analyzed in order to deter- 

 mine whether the output of the same firm is of uniform composition. 

 As the purpose of the investigation was to show the general condition 

 of the trade during 1907-8, more particularly as a preliminary to 

 other studies, the names of the manufacturers are not given, but all 

 of the samples from one firm are designated by the same letter, that 

 they may be compared. 



