SANGER. — VOLATILE COMPOUNDS OP ARSENIC. 115 



the method of examination for arsenic would alone have deprived 

 them of value. Not finding, by his unskilful test, any arsenic in the 

 dust, he concludes at once that arsenic cannot be liberated at all, and 

 uses the result as an argument against the possibility of arsenical 

 poisoning from wall papers. 



Arnd,* in 1855, offers the following remarkable explanation : " Ar- 

 senates are decomposed by carbon dioxide, setting free arsenious 

 oxide which is volatilized. By evaporation of the water from the 

 paste, arsenical particles are carried off. Sulphide of arsenic on a 

 lime ground is decomposed with evolution of arseniuretted hydrogen, 

 as the lime takes away the sulphur, forming calcic sulphide." 



Eulenbergf mentions the following experiment made in 1857 by 

 Halley and Williams, but I can find no account of it or reference to 

 it elsewhere. Several sheets of filter paper were soaked in ammonia- 

 cal argentic nitrate and hung up in a closed room of which the paper 

 contained . Schweinfurth green. Gas lights were kept burning ten 

 hours, and after they were put out the room was kept closed ten 

 hours longer. The papers, which were blackened, were digested with 

 hydrochloric acid for thirty minutes, and a piece of copper was laid in 

 the solution. A gray deposit was formed on the copper, and the 

 latter, after being washed and dried, was heated in a bulb tube. 

 A white ring was obtained and said to be arsenic, though no further 

 proof was given. Yet, if it were arsenic, which is not decided, it 

 mi^ht have had its source in the dust of the room, as well as from a 

 volatile compound. 



Halley, in 1858, in a letter to the London Times, $ tests the air 

 of a room containing an arsenical wall paper by merely hanging up 

 sheets of paper soaked in ammoniacal argentic nitrate, in which he 

 observes after some time the formation of numerous "well defined 

 crystals of arsenious oxide, visible under a low power microscope." 

 I am inclined to think that this experiment is merely the foregoing, 

 subjected to a newspaper condensation, which has omitted essential 

 details. 



Campbell, § in 1858, made the following experiment. Strips of arsen- 

 ical paper, about one square foot in all, were placed in a bottle contain- 

 in"' a thermometer and fitted with a double bored cork. Through one 



* Verhandl. d. Verein f. Staatsarzneiwissensch. in Berlin, 1855, 1. 47. 



t Loc. cit., p. 416. 



J Pliarmac. Journ. and Transactions, 1858, p. 428. 



§ Ibid., p. 520. 



