ARSENIC. 
§ 742.] 
of arsenious acid, and in such a case is, of course, more poisonous. King’s 
yellow, if pure, yields to water nothing which gives any arsenical reaction. 
A blue pigment, termed mineral blue , consists of about equal parts 
of arsenite of copper and potash, and should contain 38-7 per cent, of 
metallic arsenic (=to 51-35 As 2 0 3 H) and 15-6 of copper. 
Schweinfurt green (syn. Emerald-green), (CuAs 2 0 4 )3Cu(C2H 3 0 2 ) 2 , is 
a cupric arsenite and acetate, and should contain 25 per cent, of copper 
and 58-4 per cent, of arsenious acid. In analysis, the copper in this 
compound is readily separated from the arsenic by first oxidising with 
nitric acid, and then adding to the nitric acid solution ammonia, until 
the blue colour remains unchanged. At this point ammonium oxalate 
is added in excess, the solution is just acidified by hydrochloric or nitric 
acid, and, on standing, the copper separates completely (or almost so) as 
oxalate, the arsenic remaining in solution. 
Another method is to pass SH 2 to saturation, collect the sulphides on 
a filter, and, after washing and drying the mixed sulphides, oxidise with 
fuming nitric acid, evaporate to dryness, and again treat with nitric acid. 
The residue is fused with soda and potassic nitrate, the fused mass is 
dissolved in water, acidulated with nitric acid, and the copper is pre¬ 
cipitated by potash ; the solution is filtered, and in the filtrate the arsenic 
is precipitated as ammonio-magnesian arseniate or as trisulphide. 1 
Scheele’s green (CuHAs0 3 ) is a hydrocupric arsenite, and contains 
52-8 per cent, of arsenious anhydride and 33-8 per cent, of copper. 
6. External Applications of Arsenic for Sheep, etc. —Many of these 
are simply solutions of arsenic, the solution being made by the farmer. 
Most of the yellow sheep-dipping compounds of commerce are made up 
either of impure carbonate of potash, or of soda ash, arsenic, soft soap, 
and sulphur. The French bain de tersier is composed of :— 
Arsenious acid 
Ferrous sulphate 
Peroxide of iron 
Gentian powder 
1-00 kgrm. 
1000 „ 
0-20 
99 
This is to be added to 100 kgrms. of water. Another common applica¬ 
tion consists of alum and arsenic (10 or 12 to 1), dissolved in two or 
three hundred parts of water. 
7. Arsenical Soaps, etc. —Arsenic is used in preserving the skins of 
animals. One of the compounds for this purpose, known under the name 
of Becceur’s arsenical soap, has the following composition :— 
Camphor . 
Arsenic 
Carbonate of potash 
Lime 2 
3-4 
20-2 
per cent. 
99 
56-2 
20-2 
99 
99 
1 P. Gucci, Chem. Centrbl., 1887, p. 1528. 
2 The dust from the preserved skins of animals has caused at least one case 
of poisoning. Ann. d'Hyg. Pub. et de Med. Leg., 2 e ser., 1870, xxxiii. 314. 
