182 
DR. GLADSTONE ON CIRCUMSTANCES MODIFYING 
Ferric Sulphocyanide. 
If a soluble sulphocyanide be mixed with a ferric salt, a red solution results indi- 
cating the formation of the ferric sulphocyanide. Suppose three equivalents of the 
sulphocyanide be mixed with one equivalent of the metallic salt, we have the exact 
proportions theoretically necessary for the production of Fcg, SSg Cy. The first ques- 
tion to be solved is, — In such a case does the whole of the iron and of the sulpho- 
cyanogen combine as ferric sulphocyanide, or does it not? If Bergman’s view be 
correct, the decomposition v/ill be in accordance with the following simple formula 
(Rd standing for any salt radicle, and M for any metal) — 
Fcg Rdg-l-SM, Sg Cy=Fe 2 , SSg Cy-j-SM Rd ; 
and it will not matter what metal is represented by M, or what salt radicle by Rd, 
provided only that a double decomposition does take place. Beside which, the addi- 
tion of a larger quantity of either one of the original compounds will not increase 
the colour, for there is but one sesquisulphocyanide of iron, and the whole of the 
iron, or of the siilphocyanogen (as the case may be), has been already saturated. If, 
however, Berthollet’s view be correct, the decomposition will not be so complete 
as to form merely Feg, 883 Cy and 3M Rd, but in addition to these two salts there will 
be certain portions of the two original salts still remaining as such in the solution. 
This will become manifest by an amount of colour being obtained which is not equal 
to what would have been produced had the whole of the iron entered into combina- 
tion with the sulphocyanogen : and the requirements of the theory will lead us more- 
over to expect that the amount of ferric sulphocyanide (and consequently the depth 
of colour) will depend in a great measure on the nature of M or Rd, and will be 
increased by each addition of either the soluble sulphocyanide or the ferric salt. 
The following were the preliminaries for the complete determination of this 
question : — 
Solutions of the ferric chloride, nitrate, sulphate, acetate, and citrate were pre- 
pared, each containing an amount of iron equivalent to 0'162grm. of sesquioxide in 
every 1000 grain measures of water. The salts were made principally by dissolving- 
pure hydrated ferric oxide in the pure acid ; but it was found very difficult to obtain 
them of a definite constitution. Yet those employed, if not absolutely coinciding 
with the expression FegRda, came very close to it ; and fortunately the general result 
will be found not to depend upon great precision in the perfectly atomic composition 
of the iron salts. A solution of pure sulphocyanide of potassium was prepared con- 
taining 2-376 grms. of the salt in every 1000 gr. measures, that is to say, twelve equi- 
valents in the same quantity of solution as contained one equivalent of the ferric 
salts. Solutions of other potash salts, containing the same amount of potassium in 
lOOOgr. measures, were prepared; as also solutions of known strength of sulpho- 
cyanide of barium and of mercury, and of hydrosulphocyanic acid. 
In order to compare the depth of colour produced on the admixture of these solu- 
