67 O POISONS : THEIR EFFECTS AND DETECTION. [§ 853 . 
1. The solution, poured into a large volume of warm distilled water, 
gives a crystalline precipitate of subnitrate of bismuth. The only metal 
giving a similar reaction is antimony, and this is excluded by the method 
employed. 
2. The filtered fluid gives on addition of sodic chloride a precipitate 
of oxychloride. This again is distinguished from oxychloride of antimony 
by its insolubility in tartaric acid. 
3. Any bismuth precipitate, fused with soda on charcoal, gives a 
brittle bead of bismuth. The charcoal is coated, whilst warm, a dark 
orange-yellow ; on cooling, citron-yellow. 
4. The bead may be identified by powdering it, placing it in a short 
subliming tube, and passing over it dry chlorine. The powder first turns 
black, then melts to an amber-yellow fluid, and finally, by prolonged 
heating, sublimes as terchloride of bismuth. 
5. A very delicate test proposed by Abel and Field, in 1862, 1 
specially for the detection of bismuth in copper (but by no means con¬ 
fined to mineral analysis), utilises the fact that, if iodide of lead be 
precipitated from a fluid containing the least trace of bismuth, instead of 
the yellow iodide the scales assume a dark orange to a crimson tint. A 
solution of nitrate of lead is used ; to the nitric acid solution ammonia 
and carbonate of ammonia are added ; the precipitate is washed, and 
dissolved in acetic acid ; and, finally, excess of iodide of potassium is 
added. It is said that thus so small a quantity as *00025 grm. may be 
detected in copper with the greatest ease, the iodide of lead becoming 
dark orange ; *001 grain imparts a reddish-brown tinge, and *01 grain 
a crimson. 
6. A solution of bismuth salt, which must contain no free HC1, when 
treated with 10 parts of water, 2 of potassium iodide, and 1 part of 
cinchonine, gives a red-orange precipitate of cinchonine iod.-bismuth. 2 
7. Van KobelFs test, as modified by Hutchings, 3 and proposed more 
especially for the detection of bismuth in minerals, is capable of being 
applied to any solid compound suspected of containing the metal. A 
mixture of precipitated and purified cuprous iodide with an equal 
volume of flowers of sulphur is prepared, and 2 parts of this mixture 
are made into a paste with 1 part of the substance, and heated on a slip 
of charcoal on an aluminium support by the blowpipe flame. If bismuth 
be present, the red bismuth iodide will sublime, and on clean aluminium 
is easily distinguishable. 
Micro-Chemical Test.— Either caesium or rubidium chloride, added 
to a hydrochloric acid solution of bismuth salts, gives a double chloride 
crystallising in hexagonal tables. 
1 Journ. Chem. Soc., xiv. 290, 1862 ; Chem. News, xxxvi. 261. 
2 E. Legar, Bull, de la Soc. Chim., iv. 91, 1888. 
3 Chem. News, xxxvi. 249. 
