THE PRESENCE OF ARSENIC IN HOPS. 3 



samples were collected just before the crop was picked and were 

 dried carefully in the open air ; thus avoiding any possible chance of 

 contamination from the sulphur. For comparison with the field 

 samples thus prepared, samples of the hops from these fields, as well 

 as samples of the sulphur used to bleach them, were taken at the kilns. 

 Samples of kiln-dried hops and, when possible, samples of the sulphur 

 used in bleaching them, were also secured from several widely sepa- 

 rated localities. The soils on which these hops were produced varied 

 from the alluvial sandy loam along the river to the clay loam of the 

 uplands and represented practically all the soil types ordinarily 

 used for the production of hops. 



Some samples of Fuggle^ an early variety, also were collected for 

 comparison as to arsenic content with the later variety known as 

 Cluster or English Cluster. 



ANALYSIS OF MATERIALS. 



Arsenic was determined by the modified Gutzeit method, following 

 in general the procedure outlined by C. R. Smith. 1 A discussion of 

 the method and of the reasons for adopting the exact details followed 

 in this work will be published elsewhere. 2 The hops were treated with 

 nitric and sulphuric acids to destroy organic, matter. The sulphur 

 was treated with bromin 3 and the arsenic separated from the sul- 

 phur bromid by extraction with bromin water. In all cases arsenic 

 was precipitated as ammonium magnesium arsenate by adding mi- 

 crocosmic salt, magnesia mixture, and ammonia. The precipitate of 

 phosphate and arsenate was dissolved in sulphuric or hydrochloric 

 acid, the arsenic reduced by stannous chlorid, and arsin generated 

 by the use of zinc. The arsin was allowed to pass over a strip of 

 paper containing mercuric bromid, making a brown stain, the length 

 of which depended upon the quantity of arsenic in the sample. 

 When large quantities of arsenic were present the arsin was passed 

 into a solution of mercuric chlorid; the precipitated mercurous 

 chlorid was filtered on ignited asbestos in a Gooch crucible, dried, and 

 weighed. 



RESULTS OF ANALYSES. 



The results of the analyses of the field samples, dried in the sun 

 without contact with sulphur fumes, are given in Table I. Although 

 these samples came from widely separated yards and represented two 

 varieties of hops, little difference is shown in their arsenic content, 

 which is uniformly small. The analysis of samples 176, 201, and 202, 



1 Smith, C. R. The determination of arsenic. U. S. Dept. Agr., Bur. Chem. Cir. 102, 12 p., 2 fig. 1912. 



2 Collins, W. D. C. R. Smith's method for the determination of arsenic (with special reference to the 

 determination of arsenic in hops and in sulphur). Presented at the meeting of the Assoc. Off. Agr. 

 Chem., Nov. 20-22, 1916. (To be published in Jour. Assoc. Off. Agr. Chem.) 



3 Smith, W. Estimation of selenium in sulfur . In Jour. Indus, and Engin. Chem., v. 7, no. 10, p. 849- 

 850. 1915. 



