NOTES ON THE CIILOllIDES OF IRON. 
399- 
Properties of a semi-spirituous Solution of Per chloride of Iron. —Wlien the pure 
solution of perchloride above described is mixed with three times its volume of 
spirit of wine, a clear liquid of rich brown colour is obtained, similar in per¬ 
centage of iron, water, and spirit, to the fluid dignified by the name of tincture 
of perchloride of iron in the British and other Pharmacopoeias and in pharmacy 
generally. This aquo-spirituous solution of perchloride of iron is very unstable,, 
the spirit exerting exactly the opposite influence to that it always should and 
generally does exert in tinctures. Alcohol is generally added to liquids to retard 
or prevent change, or is used as a solvent for substances insoluble or only par¬ 
tially soluble in water. Now perchloride of iron is perfectly soluble in water, 
and the solution is stable ; for these reasons the addition of alcohol to such a so¬ 
lution when it is to be used in medicines is entirely unnecessary and should not 
therefore be practised. But when, in addition to these reasons for its exclusion, 
it is known that in the course of a few days it and the perchloride of iron so re¬ 
act on each other that the solution becomes turbid, deposits much iron, and is 
unfit for use in medicine, its exclusion becomes imperative. Compounders of 
medicine have hitherto made a mistake in placing a spirituous solution in the 
hands of prescribers of medicine. They should now prepare an aqueous solu¬ 
tion of similar strength, and induce the latter to discontinue the use of the 
spirituous. Meanwhile, 3 ust as the rotten supports of a bridge may be strengthened 
by spurs and trusses, so the breaking up of tincture of perchloride of iron, due 
to the presence of the body which should itself prevent decomposition, may be 
prevented by the addition of certain chemical supports. The simplest and least 
objectionable of these is hydrochloric acid. As a result of many experiments, 
which I need not describe, I find that if not less than four drops of the ordi¬ 
nary hydrochloric acid be added to every ounce of this semi-spirituous solution 
of pure perchloride of iron, no decomposition occurs ; at least I find no evident 
change after keeping such a solution for six months, though, doubtless, the 
other decomposition to which I have referred, namely, the formation of proto¬ 
salt and a chlorinated ethereal body, has progressed to some extent. 
I do not recommend this method of making a tolerably stable tincture of 
perchloride of iron ; for a spirituous solution ought never to be used in phar¬ 
macy. I simply refer to it as indicative of the cause of that failure or success 
which most persons have experienced in attempting to make the tincture, and 
offer it as indicative of the object to be aimed at in preparing the tincture so 
long as medical practitioners continue to prescribe that liquid.* 
Second Method. 
With a knowledge of these properties of the chlorides of iron and their solu¬ 
tions, we may now examine other processes for making solutions of perchloride 
of iron of definite strength. The strengths to which I more especially allude 
are those already mentioned, namely, an aqueous solution, one hundred fluid 
parts of which contain twenty solid parts of metallic iron, and a spirituous so¬ 
lution, one hundred fluid parts of which contain five solid parts of iron. These 
are, respectively, Liquor' Ferri Berchloridi and Tinctura Ferri Perchloridi of the 
British Pharmacopoeia. 
In the above method of making perchloride of iron from its elements, the 
chlorine was obtained from hydrochloric acid by the agency of binoxide of 
* Since the above was written I find that at King’s College Hospital the tincture has for 
many years been discarded in favour of an aqueous solution of similar strength. Dr. 
Lionel Beale, F.R.S., says (Med. Times and Gaz., Jan. 14, 1865), “The composition of this 
solution is just the same as that of the tincture, except that water is used instead of spirit. 
It has been in constant use in our hospital for the last eight or nine years.” Correspon¬ 
dents of the £ Lancet ’ have also, lately, advocated the employment of aqueous rather than 
spirituous solutions of perchloride of iron. 
