PART IX.—INORGANIC POISONS. 
I.—PRECIPITATED FROM A HYDROCHLORIC ACID SOLU¬ 
TION BY HYDRIC SULPHIDE—PRECIPITATE YELLOW 
OR ORANGE. 1 
Arsenic—Antimony—Cadmium. 
1. ARSENIC. 
§ 733. Metallic Arsenic, atomic weight, 75 ; specific gravity of 
amorphous arsenic, 4*7 ; of crystalline, 5-7 ; sublimes without fusion in 
small quantities at 110° (230° F.) [Guy). It occurs in commerce in whitish- 
grey, somewhat brittle, crystalline masses, and is obtained by subjecting 
arsenical pyrites to sublimation in earthen retorts, the arsenic being 
deposited in suitable receivers on sheet iron. There is an allotropic 
variety, yellow arsenic, As 4 , obtained by subliming arsenic in a current 
of C0 2 in the dark and condensing the vapours on a surface cooled to 
0° ; yellow arsenic has an onion-like odour, is soluble in CS 2 , which 
solution, on evaporation, leaves it in rhombohedral dodecahedrons iso- 
morphous with crystals of white phosphorus ; it is rapidly changed with 
evolution of heat into ordinary amorphous arsenic. Metallic arsenic, 
according to the experiments of Paschkis and Obermayer {Med. Jahrb. 
Wien, 1888), is capable of being absorbed by the skin, and then undergoes 
oxidation and produces poisonous effects. Volatilised metallic arsenic 
is easily transformed in the presence of air into arsenious acid, and is 
therefore intensely poisonous. 
§ 734. Arsenious Anhydride—Arsenious Acid—White Arsenic— 
Arsenic, As 2 0 3 = 198 ; specific gravity of vapour, 13-85 ; specific gravity 
1 Fresenius has pointed out that sulphur may mask small quantities of arsenic, 
antimony, tin, etc., and he recommends that the turbid liquid in which apparently 
nothing but sulphur has separated should be treated as follows :—A test tube is half 
filled with the liquid, and then a couple of c.c. of petroleum ether or of benzene added, 
the tube closed by the thumb, and the contents well shaken. The sulphur dissolves, 
and is held in solution by the solvent, which latter forms a clear layer upper. If 
traces of a metallic sulphide were mixed with the sulphur, thin coloured films are 
seen at the junction of the two layers, and the sulphides may also coat the tube 
above the level of the liquid with a slight faintly coloured pellicle ( Chem . News, 
Jan. 4, 1895). 
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