272 EXAMINATION FOR ARSENIC 



It is very important, in connection with this test 

 (Marsh's) to remember that antimony also, whether as 

 teroxide, or as antimonic acid, and especially when in 

 solution in the form of a salt, yields under the same 

 conditions as arsenic, a gaseous antimonetted hydrogen, 

 which deposits upon the heated tube, and upon porce- 

 lain, a mirror and spots very similar to those obtained 

 with arsenic. This fact assumes so much greater im- 

 portance, when it is remembered that preparations of 

 antimony, especially tartar emetic, are administered as 

 internal remedies, so that, in such cases, metallic mir- 

 rors are obtained, similar to those of arsenic, but con- 

 sisting, not of that metal but of antimony. On the 

 other hand, it must not be forgotten that commercial 

 arsenic, as it is employed for poisoning, frequently 

 contains antimony. 



If the question be merely whether a metallic mirror 

 consist of arsenic or antimony, it may be readily de- 

 cided. The arsenic may be easily recognized by the 

 reactions mentioned above, while the antimony-mirror 

 presents very different characters. The antimony- 

 mirror has a lighter color, and is more lustrous than 

 that of arsenic; the antimony spots are darker and have 

 often a tinge of blue. Antimony is not nearly so easily 

 volatilized as arsenic, and although both mirrors may be 

 chased from one part of the tube to another, there is a 

 great difference in the heat necessary in the two cases. 

 A very striking difference between the two deposits 

 is seen in their behavior when heated ; the mirror of 

 antimony, before volatilizing, fuses into small lustrotfs 

 globules, which may, in all cases, be seen with the aid 

 of a lens; the arsenic, however, exhibits no sign of 

 fusion. The most characteristic distinction is the pro- 

 duction of the garlic odor when the arsenic is volatilized 

 while the antimony passes off in vapor without any 

 perceptible odor. If that portion of the tube which 

 contains the mirror be heated while the hydrogen is 



