648 
UXGUENTUM HYDRARGYRI NITRATIS. 
leave some doubt on the other head. Also, I should be glad to learn if this 
mode effectually exhausts the volatile principles of the ingredients treated. 
I am, Gentlemen, yours faithfully, 
Clifton , May 24, 1865. Richard W. Giles. 
TJNGUENTUM HYDRARGYRI NITRATIS. 
TO THE EDITORS OF THE PHARMACEUTICAL JOURNAL. 
Gentlemen,—I am surprised to see in the Pharmaceutical Journal for April 
an article by Mr. Donovan, in -which he states that— 
“There is no known formula for preparing citrine ointment, which will always pre¬ 
sent the same appearance and possess the same properties, and a very short time is ade¬ 
quate to induce changes to a certain amount. This ointment may he viewed as a metallic 
soap, mixed with that compound which Fourcroy designates oxygenized pomatum. 
Oxide of mercury, like other metallic oxides, forms a soap with the fatty acids. Berthollct 
produced such a compound by decomposing corrosive sublimate by means of solution 
of soap ; but it was not permanent, in process of time it became slate-coloured. A soap 
may be formed of an analogous constitution by heatiug finely-levigated peroxide of 
mercury with lard^; but the soap thus produced undergoes the same changes as that of 
Berthollet, first becoming brown, and ultimately slate-coloured. Hence, the ointment 
of red precipitate cannot be kept unchanged in the apothecary’s shop. Citrine oint¬ 
ment is similarly acted upon by time ; if its colour be ever so bright a yellow at first, 
it soon becomes dull, and by degrees tends to the same alterations as those already 
mentioned.” 
As this statement is quite contrary to my opinion, based on the experience of 
its manufacture for ten years, and as Mr. Donovan’s experience coincides with 
that of several of my Pharmaceutic friends, my choice of formula and modus 
opercindi may not be uninteresting to some of your readers. With regard to 
the red precipitate ointment, Mr. Donovan, as also the compilers of the British 
Pharmacopoeia, appears to have entirely overlooked a very excellent recipe pub¬ 
lished some few years ago in this Journal by Mr. Barber, in which he recom¬ 
mends the substitution of yellow for white wax. I have prepared the ointment 
in the manner directed bv him, and have found no perceptible change in colour 
during many months. 
The formula for citrine ointment I prefer is that of the P. L., 1851, which 
if strictly adhered to produces a capital ointment, which will retain its yellow 
colour for a long time. I used a piece a few days ago, which I prepared in the 
early part of last year, in which there was not a trace of reduced mercury per¬ 
ceptible to the naked eye. I have made the quantity ordered in the London 
Pharmacopoeia, but I generally operate on half that quantity, and as I do not 
recollect ever having failed in preparing the ointment, my attention was specially 
called to my method the last time I made it. I tried to call to mind what I did 
on former occasions, but felt sure I never bestowed very great care upon it. 
I took a 6oz. green flint oval bottle, weighed one ounce of mercury accurately 
(not a very easy matter to a novice), put it into the bottle, which I took into the 
open air, measured two ounces of nitric acid, poured it on the quicksilver. I 
then put some water on a gas furnace to form a -water bath, and having weighed 
the lard and measured the oil, put them into a 2 lb. white pot, and placed the pot 
in the hot water; directly the lard (common bladder lard, without salt) was melted 
I went out to get my solution, and found the mercury had disappeared and the 
liquid still warm. I removed the pot from the water bath, poured in the solution of 
mercury, and stirred them together with a piece of firewood (deal) for a minute or 
