NoTomber 19 , 1870 .] THE PHARMACEUTICAL JOURNAL AND TRANSACTIONS. 
417 
hyposulphite requires a correction, lest any of the iodine 
employed should have been consumed by sulphurous 
acid. The direct estimation of the S0 2 is based upon 
the fact that while iodine oxidizes hyposulphurous acid 
into tetrathionic acid, it converts sulphurous acid directly 
into sulphuric acid; therefore, by estimating the sul¬ 
phuric acid so formed, we are enabled to calculate with 
facility the amount of sulphurous acid from which it was 
derived. Further, the amount of sulphurous acid being 
known, the iodine required for its complete oxidation is 
known also; the weight of this latter being deducted 
from the total weight of iodine employed, the remainder 
represents correctly the proportion of iodine consumed 
by the hyposulphite. 
In no single instance was any potassic sulphite de¬ 
tected in solution of sulphurated potash; the numbers 
obtained in the analyses after oxidation with iodine, 
always exactly corresponded with those yielded by the 
estimation of the sulphuric acid originally present. 
Estimation of the Sulphate. —About seven grammes were 
dissolved in a small quantity of water, and the solution 
completely decomposed by addition of dilute hydrochloric 
acid. A gentle heat was applied to volatilize sulphuretted 
hydrogen and sulphurous gases. After filtering off and 
washing the precipitated sulphur, the sulphuric acid in 
the filtrate was estimated with baric chloride. 
Estimation of the Carbonate .—6 - 5 grammes were dis¬ 
solved in water, and directly precipitated with excess of 
baric chloride. The precipitate consisted of baric car¬ 
bonate, sulphate and a small quantity of the sparingly- 
soluble hyposulphite; this was washed with distilled 
water, transferred to the usual carbonic anhydride appa¬ 
ratus, a little potassic chromate added to effect the oxi¬ 
dation of any hyposulphite which might chance to be 
present, and the carbonic anhydride determined by loss 
in the usual way. 
Estimation of the Total Potassium. —Two grammes of 
the salt having been weighed in a porcelain crucible, the 
latter was very slowly and carefully brought to a red 
heat so as to decompose the hyposulphite, and at the 
same time convert nearly the whole of the sulphide pre¬ 
sent into sulphate. After allowing the crucible to cool 
slightly, a few drops of nitric acid were added, and the 
whole evaporated to dryness. The subsequent addition 
of a drop of strong sulphuric acid ensured the conversion 
of the whole of the salt into sulphate, and the excess of 
sulphuric acid being expelled by a red heat with the 
assistance of ammonic carbonate, the potassium was 
weighed in the form of sulphate. 
I give the theoretical percentage composition of sul¬ 
phurated potash, supposing it to be formed according to 
the equation— 
Sulphur .... 
25-45 
Potassium . . . 
17-21 
Pot. Hyposulphite 
21-56 
,, Sulphate . . 
3-38 
„ Carbonate . . 
32-72 
100-32 
Excess . . . 
•32 
100-00 
Sulphur .... 
28-17 
Potassium . . . 
22-65 
Pot. Hyposulphite. 
38-00 
„ Sulphate . . 
2-34 
,, Carbonate . . 
7-50 
Ferrous Sulphide . 
•92 
99-58 
Loss .... 
•42 
100-00 
Sulphur .... 
28-32 
Potassium . . . 
20-20 
Pot. Hyposulphite. 
31-82 
„ Sulphate . . 
4-32 
,, Carbonate . . 
14-09 
Ferrous Sulphide . 
1-00 
99-75 
Loss .... 
•25 
100-00 
Sample “A” has been very carefully prepared; it 
contains no carbonate, only a trace of sulphate, and the 
full percentage of sulphide. All the other samples con¬ 
tain carbonate, especially “B,” which latter is a very 
indifferent preparation, containing not less than 32 per 
cent, of undecomposed carbonate, with a proportional 
decrease in the amount of sulphide. 
The ratio of potassium to sulphur in potassic trisul¬ 
phide is 78 of potassium to 96 of sulphur. In the fore¬ 
going analyses the ratio, as might be expected, is not 
quite so uniform, at the same time it is sufficiently so to 
show that the potassium exists in the salt principally as 
trisulphide admixed with a certain varying proportion of 
tetra- or pentasulphide. 
Ratio in A . . . . 78 to 111 
„ B .... 78 to 115 
„ C .... 78 to 97 
„ D .... 78 to 109 
3 Ko C 0 3 + 4 S 2 = Ko S 2 0 3 -f 2 K 2 S 3 + 3 C 0 2 , 
but the Pharmacopoeia orders a slight excess of potassic 
carbonate: — 
Sulphur . . . 
Potassium . .. 
Pot. Hyposulph. 
35-68 \ 
29-00 j 
35-32 
in combination. 
100-00 
The following are the results of the analysis of four 
distinct samples, A, B, C, D :— 
A. Sulphur . . . , 
Potassium . . 
Pot. Hyposulphite 
„ Sulphate . 
95.ys | potassic sulphide. 
38-32 
0-87 
100-60 
Excess ... -60 
100-00 
In sample <C B,” owing to the deficiency of potassium 
in combination with the sulphur-, due to imperfect pre¬ 
paration, the ratio more nearly approaches tetrasulphide 
than trisulphide of potassium. 
I append the analysis of one sample in which com¬ 
plete decomposition has taken place, owing to its having- 
been kept for a period of about nine months in a bottle 
with an imperfectly-fitting- stopper. As will be seen, 
the potassic sulphide has entirely disappeared, having 
been oxidized principally to hyposulphite and sulphate 
with separation of sulphur. 
E. Potassic sulphate . . . . 18-06 
,, hyposulphite . . 51-60 
Free sulphur.15*42 
Ferrous sulphide . . . . 1*73 
Potassic carbonate . . . 3-10 
Moisture.8-89 
98-81 
Loss. 
100-00 
