PREPARATION OF LIQ. FERUI PERCHLOR., P.R. 
551 
ment when the iron is dissolved. When the nitric acid is added to this solution, 
the compound immediately assumes an intense inky-black appearance. Heat 
being now applied, brisk effervescence takes place, and continues till the liquid 
suddenly, and without any previous warning, boils up with great violence, 
throwing up a dense cloud of nitrous fumes. This violent action lasts only for 
a few seconds, and the moment it has subsided the liquid is seen to have assume 
the beautiful orange-brown colour, characteristic of solutions of perchloride of 
iron. The evaporation now' proceeds quietly on to the close. Now, this sudden 
boiling up is the stone over which most of those in whose hands the process has 
failed have probably stumbled. Those, of course, who are chemical experts, or 
who have been in the habit of preparing persulphate of iron, expect it, and wait 
for it, and know that the process w r ill not be complete until it takes place. But 
it may not be so with the pharmaceutist who has not been accustomed to 
chemical operations, and he would probably remove the heat before the action 
was terminated, and thus produce a mixture of proto-and perchloride of iron, 
with nitrous and nitric acids. This I believe to be the story of most of the 
failures which have been recorded. Why they have omitted in the Pharma¬ 
copoeia to mention this sudden evolution of binoxide of nitrogen in describing the 
process under consideration, when they have not failed to do so in that for pre¬ 
paring persulphate of iron, is more than can be accounted for, but it is one of 
the mucli-to-be-regretted omissions in that otherwise admirable book. 
In answer to the question, is the process of which the formula given in the 
British Pharmacopoeia is an adaptation, an efficient one? I would most deci¬ 
dedly say that it is. I do not wish it to be understood that I consider it per¬ 
fect, but I do think that the nitro-hydrochloric process (as it has been styled) is 
the most efficient that has yet been devised. In this month’s number of the 
4 Pharmaceutical Journal,’ Dr. Attfield says no; but his reasons for saying so 
appear to me to be very weak. We do not want a product absolutely pure ; 
what we want is one that will keep, of constant strength, an elegant appear¬ 
ance. Such a product can be obtained with careful manipulation by following 
the direction of the Pharmacopoeia, and it could perhaps be so modified that 
less careful manipulation would suffice to produce a like result. I have now a 
specimen that was made more than twelve months ago, and it is still good, so 
that there can be no doubt as to its stability. It contains no protochloride, not 
even a trace of it. It is deficient in chlorine, however, being very slightly basic ; 
so that, though it keeps well enough for a few weeks when mixed with spirit, it 
ultimately deposits a very small quantity of basic perchloride. 
For the purposes of this paper I have prepared ten ounces of solution of per¬ 
chloride of iron, strictly following the directions of the Pharmacopoeia. In order 
that every condition should be exactly as it is ordered in that work, I prepared 
my own hydrochloric acid, distilling the water required in its preparation my¬ 
self. I also prepared my own nitric acid, and accurately ascertained tbe den¬ 
sities of both acids before using them. I have here a sample of the liquor so 
produced, and of the tincture prepared with it. The tincture has been made for 
fully a month, and is still perfectly bright and free from decomposition. I have 
very carefully examined this product. It has a specific gravity of 1-433. The 
Pharmacopoeia directs it to have a density of 1*388, but there must be some mis¬ 
take here. Dr. Attfield says that a solution of the officinal strength, prepared by 
dissolving anhydrous perchloride of iron in water, has a sp. gr. of 1-432, and 
this is about the density of all the specimens I have made. Two drachms of 
this liquor yielded thirty grains of peroxide of iron by precipitation with excess of 
ammonia: it should have yielded thirty-one; but the inevitable loss by contact 
fully accounts for this deficiency. Having ascertained that it contained no pro¬ 
tochloride, I was wishful to know whether all the iron it contained was in the 
condition of Fe„ Cl b . To find this out, I precipitated two drachms of the liquor 
