SANGER. — VOLATILE COMPOUNDS OF ARSENIC. 117 



9. 600 grains (39 grams) of emerald-green were distributed in a 

 lot of cotton wool and placed in a jar, into which a tube was plunged 

 containing cotton wool and connected with the silver solution. Air 

 was drawn through at 32° for some time, but no arsenic was detected 

 in the solution. 



Phillips,* in 1858, repeated the experiment of Halley. Two clos- 

 ets were used, one containing 48 sip ft. (4.46 sq. m.) of a paper 

 containing 11.8 grains arsenious oxide, as Schweinfurth green, to 

 the square foot (8.3 grams per square meter), and another containing 

 53 sq. ft. (4.92 sq. m.) of the same paper. In each closet were placed 

 two dishes, one containing a solution of potassic hydroxide and the 

 other ammoniacal argentic nitrate, besides a sheet of paper saturated 

 with the latter. The closets were closed 72 hours and <ras was 

 burned 45 hours in one, the temperature being about 25°. No ar- 

 senic was found in the solutions by Marsh's test, but the method of 

 preparing the solutions for the test is not given. The paper also 

 contained no arsenic, but was of course dark, and contained crystals 

 of argentic nitrate. Phillips considered that his test proved the 

 absence of the vapor of arsenious oxide, but he has apparently proved 

 the absence of any arsenical dust. The use of the Marsh test is suf- 

 ficient to account for this, as the amount of dust that might fall in 72 

 hours from such a paper would quite possibly show no arsenic by the 

 simple Marsh test. As a test for the presence of a gaseous compound 

 like arseniuretted hydrogen, such an experiment is of no value. 



Paul,f in the same year, thinks that Campbell's and Abel's work 

 disproves the idea that arsenic is volatilized, and concludes from the 

 negative results that the arsenic cannot leave the paper at all, paying 

 no attention to the possibility of the detachment of arsenical dust. 



Oppenheimer,$ in 1859, was the first to show the presence of arsenic 

 in the dust of a room. 



Schmidt and Bretschneider,§ in 1859, placed a mixture of Schwein- 

 furth green, meal, and water in a large flask closed by a double bored 

 cork, through one boring of which a tube led to an argentic nitrate 

 solution protected from the light, the other hole being presumably 

 fitted with a tube reaching under the mixture. In three similar 

 flasks the same mixture was placed, and to them were added, respect- 



* Jour. Franklin Inst., [3], XXXVI. 307; also Lond. Civ. Eng. and Arch. 

 Journ., 1858. 



t Pliarmac. Jour, and Transactions, 1858, p. 616. 



t Ref. by Eulenberg, loc. cit., to Heidelberger Jabrb. d. Lit., 1859, p. 810. 



§ Untersucli. z. Naturlebre d. Mensch. u. Tbier. v. Molescbott, VI. 14G. 



