298 PEOCEEDINGS OF THE AMEKICAN ACADEMY. 



Thomson^ attempted to make the reaction quantitative by passing 

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

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

 from the intensity of the stain produced upon it, should show the 

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

 were untrustworthy. 



Goode and Perkin ^ made a series of experiments to ascertain if the 

 Gutzeit test could be made quantitative, and if a set of standards could 

 be prepared which should be 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- 

 poses, except that a given stain might be matched with freshly 

 prepared standards. 



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

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

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

 ently 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. 



Aside 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 by vari- 

 ous amounts of arsine on either argentic nitrate or mercuric chloride 

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

 partly 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 act not against, but along a surface. The principle, there- 

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

 actions more accurately quantitative, is to allow the arsine to pass 

 over a strip of paper impregnated with mercuric chloride and to com- 

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

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



" Royal Commission on Arsenical Poisoning, Final Report, 2, 58. London, 

 Eyre and Spottiswoode, 190.3. 

 'fi Jour. Soc. Chem. Ind., 25, 507 (1006). 

 T Jour. Amer. Chem. Soc, 21, 133 (1899). 



