206 
BRITISH PHARMACEUTICAL CONFERENCE. 
IODIDES OF AMMONIUM AND CADMIUM. 
Iodide of Ammonium. 
Iodide of Cadmium. 
I. 
II. 
III. 
I. 
II. 
III. 
Carbonate . . 
0* 
0* 
o- 
o- 
o- 
i 
0. 
Sulphate. . . 
6*93 
o- 
6-02 
o- 
trace. 
o- 
Iodate . . . 
o- 
O' 
o- 
o- 
o- 
o- 
Chloride. . . 
0-07 
0-08 
0-23 
0-08 
trace. 
0-09 
Bromide. . . 
o- 
o- 
o- 
o- 
o- 
o- 
Water . . . 
4-68 
0-83 
2-43 
0-17 
0-4 
0-27 
Iodide . . . 
88-28 
98-93 
91-32 
99-68 
99-58 
99-61 
: 
i 
99-96 
99-84 
100-00 
99-93 
99-98 
99-97 
The methods adopted for the determinations were— 
1. Carbonate. By a standard solution of sulphuric acid, 10 cubic centimetres 
of which were equivalent to 0 - 05 grammes of KQ,C0 2 . 
2. Sulphate. In the usual way, by precipitation with chloride of barium. 
3. Chloride, bromide, and iodide. In the bromides, about 2 grammes of the 
salt, dissolved in water, dilute nitric acid added, and then agitated with chloro¬ 
form, more chloroform being added until the chloroform remained colourless. 
The chloroform is well washed with distilled water, and the chlorine and bro¬ 
mine determined in the aqueous solution by precipitation with silver, and after¬ 
wards heating a weighed portion of the precipitate in a current of chlorine. 
The iodine was determined by deducting the weight of the silver precipitate 
obtained after the removal of the iodine from the weight of a corresponding 
silver precipitate obtained from a portion of the original salt. 
In the iodides, the chlorine and iodine were determined by weighing the pre¬ 
cipitate by nitrate of silver, and afterwards heating a weighed portion of that 
precipitate in a current of chlorine. 
Bromine in the iodides was searched for qualitatively by mixing a portion of 
the salt, dissolved in water, with dilute sulphuric acid and a little starch-paste, 
adding fuming nitric acid, and then chlorine water, until the blue colour pro¬ 
duced by the iodine and starch disappears ; the further addition of chlorine 
water will now liberate the bromine, if present, and it may be removed by 
means of chloroform. No bromine, however, was found in any of the samples 
of the iodides. 
4. Water. By heating in the air-bath, at a temperature of 120° C., until a 
constant weight was obtained. 
The results to be deduced from the analysis are, that the bromides of ammo¬ 
nium and cadmium and iodide of cadmium are practically pure; the same cannot 
be said of the bromide of potassium ; and with regard to the iodide of ammo¬ 
nium, the principal impurity is the large quantity of sulphate found in two of 
the samples, and the presence of which in such quantities is somewhat difficult 
to account for. 
The whole of the samples, with the exception of five forwarded to me by Dr. 
Attfield, were purchased at the shops of well-known chemists and druggists, 
and varied very considerably in price, the highest-priced not being always the 
purest. 
Dr. Parkinson remarked upon the large and very improper quantity of sulphuric acid 
shown in the analyses of iodide of ammonium. It indicated pretty clearly the method 
of manufacture adopted, viz. the decomposition of sulphide of ammonium by iodine. 
