406 
GLASGOW CHEMISTS AND DRUGGISTS’ ASSOCIATION. 
absolutely necessary in Mr. Bartlett’s process, on account of the great valuation in the 
quantity of bismuth lost. 
In making liquor bismuthi, I prefer metallic bismuth before either the subcarbonate 
or subnitrate. Much has been said against its use, so that this may require a word in 
explanation. The chief objection is that, as found in commerce, it is invariably con¬ 
taminated with arsenic—an impurity from which the subcarbonate is entirely free. As 
nothing has yet been written explaining the purification of metallic bismuth in connec¬ 
tion with liquor bismuthi, it may not be out of place, or entirely without interest, to 
trace the im^purities through the process, and show how, by starting with an impure 
metal, we can have a solution of a salt of that metal chemically pure. 
Metallic bismuth of commerce is usually found to contain as impurities sulphur, ar¬ 
senic, copper, and sometimes iron. The first of these, though not poisonous in small 
quantities and uncombined, is still no less an impurity. Existing in the metal as sul¬ 
phide, it is found, when added to strong nitric acid, to comport itself in a peculiar man¬ 
ner. The acid, in the first place, decomposes the sulphide of bismuth, the sulphur 
separates in blackish flakes, then, the action becoming violent and the temperature 
raised, it is oxidized and converted into sulphuric acid, which, unless the nitric acid be 
in excess, forms insoluble sulphate of bismuth. .This, however, would not be of great 
consequence, as this salt is decomposed by ammonia in much the same manner as the 
nitrate. The result of experiments in this direction has convinced me that it is objec¬ 
tionable to employ concentrated nitric acid for dissolving-bismuth—the heat generated 
by the violent action being sufficient to determine the formation of sulphuric acid ; and 
that if a dilute acid be employed for solution, as directed, this combination does not 
take place, the whole of the sulphur being deposited, carrying with it the earthy im¬ 
purities, -which may be readily separated by filtration through tow. The quantity of sul¬ 
phur present in metallic bismuth seldom exceeds 0-5 per cent. 
Arsenic, on account of its poisonous action on the animal system, is the only impurity 
present in objectionable quantity, and the presence of v/hich in liquor bismuthi would 
interfere very much with its therapeutic action. If metallic bismuth containing arsenic 
be dissolved in strong nitric acid, the bismuth is converted into nitrate, and the arsenic 
into arsenic acid. If water be added, and the solution set in a cool place, a white pow¬ 
der is deposited, which is found to be insoluble arseniate of bismuth. If sufficient water 
has been added (from two to three volumes), all the arsenic will thus be got quit of at 
once, and the liquid only requires to be filtered to effect a separation. Supposing a part 
is still left in solution, and the process for liquor bismuthi goes on; on excess of am¬ 
monia being added to throw down the bismuth, the arsenic acid combines to form 
arseniate of ammonia—an exceedingly soluble salt, which, -with careful washing, will be 
completely removed. These are the processes for separating arsenic from bismuth for 
obtaining a chemically pure metal for experimental purposes. I, however, prefer a 
modification which, I think, is more convenient and safe. The metal is first purified as 
follows:— 
Take of metallic bismuth.1 oz., 
nitrate of potash.40 grains, 
reduce the metal to powder in a mortar, and mix intimately with the nitrate of potash 
then introduce into a crucible and fuse ; the purified metallic bismuth will occupy the 
lower part of the crucible. _ The greater part of the arsenic is thus oxidized and sepa¬ 
rated, and no arseniate of bismuth is deposited from the nitric acid solution thus render¬ 
ing filtration through paper unnecessary. The trace which is left is completely removed 
ill washing the oxide. 
The third impurity, copper, is dissolved in the nitric acid along with the bismuth, 
and remains in solution as nitrate. On the addition of ammonia, ammonio-nitrate of 
copper is precipitated—a salt soluble in excess of the precipitant, and possessing a deep 
blue colour; so that, if copper be present in any quantity, the first washings will have a 
bluish tinge. The precipitate, thrown down as directed, from a nitric acid solution, 
containing citrate of ammonia, has naturally a slight misty blue or opalescent appear-^ 
ance. This is not to be confounded with the blue colour of the liquid, as indicative of 
the presence of copper,—the latter pssing off with the first washing, -vv hile the former 
appearance will remain so long as the amorphous condition of the oxide is retained. In 
fact, to this condition, and the exceedingly minute division of the precipitate, is the 
opalescent appearance due—a crystalline oxide, possessing a beautiful white lustre. I 
