SOURCES OF ARSENIC IN DRIED HOPS. 43 



their geographical origin, as well as the desirability of a careful 

 scrutiny of the methods of cultivation and curing used abroad, par- 

 ticularly those processes in which, contrary to the American practice, 

 hops are dried over open fires. 



EXAMINATION OF HOP SOILS. 



Samples of soil from a number of American hop fields have been 

 examined for arsenic/ 1 but in no case has its presence been detected. 

 However, these results do not necessarily prove the absence of arsenic 

 from the soils of the fields examined, since the hop plant has a very 

 extensive and deep-growing root system which might very readily 

 explore soil layers unrepresented in the samples taken. 



Since traces of arsenic have been found in unsulphured hops grown 

 on some of the soils from which these samples were taken, it, may be 

 inferred that the samples were not representative of the true soil 

 conditions as just noted or that arsenic may be present in the soil in 

 quantities too minute to be detected by the ordinary methods of 

 analysis, the larger and measurable quantity in the plant being due 

 to gradual accumulation during the process of growth. 



THE ABSORPTION OF ARSENIC BY THE GROWING PLANT. 



Some early authors held that living plants did not absorb arsenic,*' 

 but numerous plants have been found to contain this substance, 

 which was doubtless derived from the soil. Nobbe *' states that only 

 a very small quantity of arsenic is taken up by plants, though ac- 

 cording to Angell e plants of rhubarb, bean, rye, and buckwheat 

 accumulate appreciable quantities from soils heavily fertilized with 

 superphosphates. Davy f found arsenic in peas, cabbages, and Swed- 

 ish turnips grown in soils mixed with superphosphates, 40 per cent of 

 which Lyttkins g states contain arsenic, in amounts varying from 0.012 

 to 0.26 per cent as estimated by Stoklasa. 7 * Collins * found that barley 



a The analysis of the soil samples was made in the Bureau of Soils, United 

 States Department of Agriculture. 



& Targioni-Tazzetti, A. Ann. Sci. Nat., ser. 3, vol. 5, pp. 177-191, 1846. — Dan- 

 berry, Chas. Quart. Jour. Chem. Soc, vol. 14, pp. 209-230, 1862. 



c Pfeffer, W. Pflanzenphysiologie, 2 ed., vol. 1, pp. 432-433, 1S97. 



d Nobbe, F., Baessler, P., and Will, H. Landw. Versuchstat., vol. 30, p. 409, 

 1884. 



e Angell, A. and A. F. Chem. and Drug., vol. 60, p. 430, 1902. 



f Davy, E. W. Philos. Magazine, vol. 18, pp. 108-113, 1S59. 



9 Lyttkins, A. Kgl. Landw. Akad. Handl., vol. 33, pp. 317-320, 1894. 



h Stoklasa, J. Ztschr. Landw. Versuch. Oesterr., vol. 1, p. 154, 1898. 



i Collins, S. H. Jour. Soc. Chem. Ind., vol. 21, pp. 222-223, 1902. 



121^iv 



