METHOD OF DETERMINING ARSENIC. 25 



A comparison of the figures given by Hills on prints and ginghams 

 with those on cotton dress goods, prints, etc., as tabulated above, 

 shows that the nonarsenical had increased only slightly, while the 

 goods containing more than 0.01 grain of arsenic per square yard had 

 decreased to a marked extent. A comparison of other figures can not 

 be made because of different methods of reporting the results. 



INVESTIGATIONS MADE IN THE BUREAU OF CHEMISTRY. 



In consequence of the great importance of this question, the pro- 

 found influences which even minute doses of arsenic exert upon health, 

 as shown by the cases cited above, and the investigations recently 

 carried on in England in regard to " arsenical beer," the authors have 

 made a further study of wall papers, fabrics, furs, etc. , both to ascer- 

 tain the present state of the American market in some locality other 

 than Massachusetts, where nearly all previous work has been done, 

 and to warn persons against certain goods which are probably injurious. 



A large number of wall papers were purchased from merchants in 

 Washington, D. C., the idea being to obtain the goods of as many 

 manufacturers as possible. Both large department stores and smaller 

 stores were visited and samples of hangings, dress fabrics, stockings, 

 furs, etc., obtained. It is believed that a representative collection of 

 most of these classes of goods has been obtained. 



METHOD OF DETERMINING ARSENIC. 



In determining arsenic a modification of the method published by 

 Sanger a was used, by which the determination of as small an amount 

 as 0.005 mg is possible. Any amount below 0.6 mg per square meter 

 is reported as a trace in the tables which follow. It would of course 

 have been possible to use the various precautions and methods of 

 procedure recently published by Bertrand, Gautier, and others, and 

 so to carry out the method that 0.0005 mg or less of arsenic could be 

 determined ; but it was thought that the method chosen was sufficiently 

 sensitive, since the most minute quantities of arsenic in papers and 

 fabrics have no significance. Following is an account of the method 

 as finally adopted : 



REAGENTS. 



The zinc, sulphuric acid, and nitric acid used in this experiment 

 must be strictly free from arsenic. To test their purity, run a blank 

 experiment using the reagents exactly in the proportions given below 

 for the actual determination. Allow the apparatus to run for at least 

 two hours, and at the end of this time, if no arsenic has been deposited, 

 the reagent is fit for use. 



"Proc. Amer. Acad. of Arts and Sci., New Series, 1891, 18: 24. 



