BISMUTHI ET AMMONITE CITRAS. 
547 
Add gradually to the citrate of bismuth water of ammonia, until the precipitate is dis¬ 
solved, and a neutral solution is obtained. Dilute this with its volume of distilled water, 
and filter through paper, returning the first portions of the filtrate, if necessary, until the 
liquid passes clear. 
To half a fluid ounce of this solution add hydrosulphate of ammonia in slight excess. 
Pour the mixture on a tared paper-filter, wash the precipitate thoroughly with distilled 
w r ater, and dry it at a temperature of 212°. Weigh the filter and its contents, deduct¬ 
ing the weight of the former to obtain that of the tersulphide of bismuth, which, in 
grains, is to form the third term in a rule-of-three proportion, thus:— 
(Bi S 3 ) (BiOg) 
261 : 237: : 
the weight of tersulphide of bismuth to that of teroxide of bismuth in half a fluid ounce 
of the solution. 
Apply the same ratio to the remainder of the liquid, and dilute it to such an extent 
that a grain of teroxide of bismuth will be contained in each fluid drachm of the finished 
solution ; seven-eighths of which measure must he made up with distilled water, and 
the remainder with alcohol. 
For preparing the citrate of bismuth, the sub carbonate is preferable to the subnitrate, 
because of its more uniform composition, as w-ell as its greater purity, at least in com¬ 
mercial specimens of these salts. The metal itself is inferior to either, as it is almost 
invariably contaminated wflth arsenic. 
The bismuth and potassa salts are employed in nearly atomic proportions for the pro¬ 
duction of a neutral citrate of bismuth ; the potassa salt, however, is in slight excess on 
account of its deliquescent nature. By using solutions considerably diluted, the precipi¬ 
tate is rendered less dense, and the washing, by displacement is thereby facilitated. 
This is a tedious part of the process, but the best means of accomplishing the purpose. 
Washing by decantation is inapplicable, for, before it has been carried to a sufficient 
•extent, a portion of the powder will remain suspended in the liquid, and can only be 
separated by boiling. 
It also entails a greater loss of the citrate of bismuth, which is slightly soluble in 
water. The absence of nitric acid from the washings can be judged of approxi¬ 
mately by the taste, but better by faintly tinging a portion of the liquid with sulphate 
of indigo, and boiling in a test-tube for a few minutes ; if the colour be retained, no 
nitric acid is present. 
In the preparation of citrate of bismuth and ammonia, the citrate of bismuth pre¬ 
viously dried is employed, in order that a concentrated solution may be obtained with¬ 
out resort to evaporation, as the heat necessary in this operation occasions a precipitate, 
caused, apparently, by a loss of ammonia. 
The solution should be spread with a brush on panes of glass to dry. 
Citrate of bismuth and ammonia, as thus prepared, is in the form of brilliant white, 
semi-translucent scales, not at all deliquescent, but readily soluble in distilled water. 
An aqueous solution of this salt, if long kept, like those of the citrates in general, is 
subject to spontaneous change. The additions of small portions of alcohol and ammonia, 
as indicated in the formulas for a solution of citrate of bismuth and ammonia, will, it is 
believed, preserve it indefinitely. The same result could probably be secured by means 
of sugar, with the additional advantage of a more agreeable taste. 
The composition of the compound salt, determined by direct analysis, is as follows :— 
BiO.j 
NH',0 
C i9 H-0 n 
237 
= 
50*11 per cent. 
= 
26 
= 
5-50 ,, 
= 
165 
= 
34*88 „ 
5 iio 
= 
45 
= 
9-51 • „ 
Bi0 3 , NII 4 0, Ci + 5 H0 
CO 
t- 
11 
100* 
The bismuth contained in the washings can be recovered by neutralizing them with 
ammonia, and treating with sulphuretted hydrogen. The precipitated tersulphide of 
bismuth, after having been washed and dried, may be reduced to the metallic state, or 
converted into the subcarbonate by suitable means. 
The writer is unable to state any facts in relation to the therapeutical properties of 
citrate of bismuth and ammonia. “ Owing to its solubility, it would undoubtedly be 
