RESEARCH FOR ARSENIC AND ANTIMONY. 
237 
vapour as it issues. Introduce slips of polished copper-foil 
(free from antimony). Continue the boiling for at least two 
hours before concluding on a negative result. In certain cases 
it may be necessary to employ from twelve to sixteen ounces of 
organic matter in one operation. 1 
2. Wash in water the pieces of copper when coated, and 
observe the violet or steel-gray film, according to the thick¬ 
ness of the metallic deposit (see page 99). 
3. Boil as many of the coated pieces of copper as can be 
collected, in a solution of pure potash, in a test-tube, occa¬ 
sionally exposing the coated surfaces to the air. The 
antimony is oxidized and dissolved off by the potash. 
4. Filter the potash-solution; acidulate with pure hydro¬ 
chloric acid, and pass into the liquid a current of sulphuretted 
hydrogen gas. An orange-red sulphide of antimony is 
precipitated. 
5. Filter the liquid and wash the precipitate. Add a few 
drops of solution of ammonia, and note its insolubility in this 
liquid. Any sulphide of arsenic is dissolved, carried through 
the filter, and may be found in the filtrate. 
6. Again wash the sulphide, and then dissolve the precipitate 
in pure hydrochloric acid, taking care to boil the liquid, in 
order to set free all the sulphur as sulphuretted h} r drogen. 
7. Having mounted a tube-apparatus for hydrogen, as 
described under arsenic (see page 341), pour the solution of 
chloride through the funnel into the tube. 
8. Test the gas evolved at the capillary end of the tube by 
a solution of nitrate of silver, and if the solution is blackened 
decompose the gas by applying a red heat to the tube. 
Remove the tube with the metallic deposit, and gently heat it 
to see whether octahedral crystals are obtained ; or whether, 
at a higher temperature, it simply forms a white amorphous 
oxide. 
The antimoniuretted hydrogen may be in sufficient quantity 
to be collected in strong nitric acid. In this case the nitric 
acid, after saturation, should be evaporated and tested, as 
already described (see page 544). 
Instead of decomposing the chloride by zinc, the operator 
may dilute it until the water forms one tenth part, and plunge 
into it a slip of pure tin, free from arsenic or antimony. If, as 
IVIillon and Laveran have shown,the liquid contains antimony, 
even in minute traces, the surface of the tin will be sooner or 
1 In one of the recent cases of antimonial poisoning at Liverpool, Dr. 
Edwards found it necessary to use thirty ounces of the liver, and to boil the 
liquid for several hours before he obtained a clear antimonial deposit on the 
copper-foil. 
