SANGER. — VOLATILE COMPOUNDS OP ARSENIC. 121 



on the air of a room. The methods of the experiment are only open 

 to criticism iu that the freedom of reagents and apparatus from arsenic 

 is not stated. 



Selnii,* in 1875, investigated the question of the formation of 

 hydrogen hy the action of mould. After showing that sulphuretted 

 hydrogen was developed in decaying organic matter over which 

 sulphur had been sprinkled, he reasoned that arseniuretted hydrogen 

 would be formed by the action of moulds on arsenical organic matter. 

 He accordingly sprinkled very finely powdered metallic arsenic over 

 a mixture of horse dung and flour, on which mould was growing 

 vigorously, and placed the preparation in a tubulated bell jar. Strips 

 of paper moistened with argentic nitrate were hung from the top of 

 the jar. The tubulus at the top was closed by a stopper with two 

 holes, carrying tubes for ingress and egress of the air that was drawn 

 through by an aspirator. After five days during which time the bell 

 jar was in the dark, the paper was found to be slightly reddened. It 

 was then treated iu a dish with potassic hj'droxide, which set free, 

 besides ammonia, a peculiar disagreeable odor. The alkaline residue 

 was then neutralized with nitric acid, evaporated with sulphuric acid 

 to destroy organic matter, and introduced into the Marsh apparatus. 

 After an hour a distinct metallic ring was obtained which, after solu- 

 tion in nitric acid and evaporation, gave a red color with argentic 

 nitrate. 



A second trial under the same conditions resulted similarly. In a 

 third and fourth, mouldy lemons were spread with arsenic dust and 

 covered by a funnel from the top of which hung strips of argentic 

 nitrate paper. After 38 hours the organic matter of the paper was 

 destroyed by nitric and sulphuric acids, and the residue, introduced 

 into the Marsh apparatus, gave a well defined ring. Five other trials 

 were made under varying conditions, and in every case a ring of 

 arsenic was obtained. In a tenth experiment arsenious oxide was 

 sprinkled on mouldy starch paste, and placed under a bell jar through 



* Ber. d. deutsch. chem. Gesells., VII. 1642 (Corresp.) ; Schmidt's Jahrbuch, 

 1875, CLXVIII. 60 ; Just, Botan. Jahresber., 1876, p. 116. All of these refer to 

 a paper of Selmi's published in the Accademia delle Scienze of Bologna, entitled 

 "Nuovo Processo Generate per la Ricerca delle Sostanze Venefiehe," in which, 

 however, the above work does not appear. I have recently obtained a reprint 

 of this article (Bologna, 1875) with which is incorporated "Osservazioni sullo 

 Sviluppo d' Idrogeno Nascente dalle Muffe," and the extract given above is from 

 the latter paper. The abstracters have evidently referred to this separate 

 monograph, and all fail to note the bearing of it upon the question of the 

 formation of a volatile arsenical compound. 



