OP Till: AMERICAN AOADKMT. 



Thi I to make the reaction quantitative bypassing 



the arsenical hydrogen through a tube in which was hung a cotton 



thread or a paper, saturated with mercuric chloride solution, which, 



I the intensity of* the stain produced upon it. should bqow the 



amount of arsenic present. Thomson states, however, that bis results 



e untrustworthy. 



ind lVrkin made a Beries of experiments to ascertain if the 

 ild be made quantitative, and it';i Bet of standards could 

 1 which Bhould he at least as permanent as the standard 

 mirrors of the Berzelius-Marsh process. Stains were made as usual 

 on paper treated with mercuric chloride, but the impossibility of mak- 

 ing them permanent led to their abandonment for quantitative pur- 

 ipl that a given stain might be matched with freshly 

 pared standards. 



irmuir, 7 in order to detect the presence of undecomposed arsine 



in the Marsh test, placed in the end of the exit tube a Blip of paper 



tied with a saturated solution of mercuric chloride. It appar- 



kly did not occur to him that this might also be used quantitatively, 



but he seems to have employed the ordinary color stains successfully 



in the approximate analysis of glycerine for arsenic. 



le from the above-quoted authors, there are doubtless many who 



have been able to use the Gutzeit reactions as a means of approximate 



analysis, but we have not met with a careful study of the conditions 



under which the reactions maybe employed quantitatively with any 



degree of accuracy. 



The chief difficulty in differentiating between stains caused byvari- 



amounl of arsine on either argentic nitrate or mercuric chloride 



paper lies in the fact that the action is partly over the surface and 



1 tly within the fibre of the paper. Further, a single layer of paper 



is not always sufficient to retain all the arsenic evolved, and stains 



from equal amounts of arsine may not always be of the same density. 



These difficulties disappear almost entirely if one allows the arsenical 



hydrogen to aot not against, but along a surface. The principle, there- 



. of the modification we suggest in order to make the Gutzeit re- 



more accurately quantitative, is to allow the arsine to p 

 ra strip of paper impregnated with mercuric chloride and tocom- 

 ■ the band of color thus obtained with a series of bands prepared 

 i known amounts of a standard solution of arsenic. We think that 



1 Royal Commission on Arsenical Poisoning, Final Keport, 2, 58. London, 

 Eyre and Spottiswoode, 1908, 



6 Jour. Sue. Chem. Ind., 25. 507 (1906). 



7 Jour < hem. Boa, 21, 138(1899). 



