2 BULLETIN 568, U. S. DEPARTMENT OF AGRICULTURE. 
occasionally found in American hops, and hop growers and handlers 
were urged to avoid the use of sulphur which could contaminate the 
hops in the process of drying and curing. Following this publication 
some hop growers made an effort to secure arsenic-free sulphur, but 
most of the growers on the Pacific coast continued to use impure 
sulphur, with the result that each year hops contaminated with 
arsenic have found their way into foreign markets. In the hops 
produced in the crop year 1914 the quantity of arsenic present was in 
many cases so much larger than usual that some English consumers 
brought the matter informally to the attention of the Bureau of 
Plant Industry and expressed the hope that American hop growers 
could be made to realize the seriousness of the situation from the 
standpoint of the foreign purchaser. 
From an inquiry made among the hop growers of the Pacific coast 
it appeared that the sulphur in common use for bleaching hops was 
generally regarded either as free from arsenic or as containing this 
element in quantities so small that no injury would result from 
its use. The soil, commercial fertilizers, and materials used in 
spraying, rather than the sulphur, were all suggested as prob- 
able sources of the arsenic in hops, but on account of the prevailing 
uncertainty as to its real source little progress apparently was made 
in the production of hops of a quality more acceptable to the foreign 
trade. The reliability of the methods used for the determination of 
small quantities of arsenic in hops and similar materials was questioned 
by some who had given careful consideration to the subject. There- 
fore, the Bureau of Plant Industry and the Bureau of Chemistry 
undertook a joint investigation in-order to establish definitely the 
source of the contamination of the hops. The field investigation and 
the collection of samples were made by the representative of the 
Bureau of Plant Industry, while the study of methods of analysis and 
the analyses of the samples collected were made in the Bureau of 
Chemistry. 
COLLECTION OF MATERIALS FOR EXAMINATION. 
The hop-producing sections of Oregon were visited during the hop 
harvest of 1915, and a carefully selected series of samples of both 
hops and sulphur was obtained. Definite information was hi hand 
regarding the origin of certain bales of hops of the crop of 1914 which 
had been rejected by English purchasers, and it was therefore possi- 
ble to locate the particular fields on which the hops in many of these 
bales were produced. It was possible also in some cases to locate 
and examine the kilns in which some of the rejected hops were dried 
and to secure samples of the sulphur used in their preparation. 
Composite samples of hops from several fields were secured by 
taking a few hops from each of a number of vines in a field. These 
