Inorganic Substances 49 



by H2S or on the precipitation of arsenites and arsenates by 

 copper sulfate in the form of the corresponding insoluble 

 cupric salts. ^^ These methods lack all specificity. Tannenholz 

 and Muir^^ have shown that the yellow precipitate obtained 

 after treatment of tissues with H2S is neither AS2S3 nor any 

 other compound of arsenic; as far as the copper method is 

 concerned, it would give positive reactions also with fatty 

 acids, phosphates, carbonates, and many proteins. 



69. Castel, P.: Bull, d'histol. appliq. a la physiol., 13:106, 1936. 



70. Tannenholz, H., and Muir, K. B.: Arch. Path., 15:789, 1933. 



