580 
UNGUENTUM HYDRARGYRI NITRATIS. 
more certain a result than the process of maceration should be overthrown, 
because chemists do not care for the trouble of teaching their apprentices 
the best method of using this valuable apparatus. I trust that some of our 
country members, many of whom I know : advocate the process, and who can 
furnish most practical results, will state their experience, that we may have 
this subject thoroughly well ventilated.—I am, yours respectfully, 
150, Oxford Street. W. A. Sanger. 
UNGUENTUM HYDRARGYRI NITRATIS, P.B. 
TO THE EDITOR OF THE PHARMACEUTICAL JOURNAL. 
Sir,—The British Pharmacopoeia is now fairly before your readers, and each of 
us has had by this time a fair opportunity of examining, and of forming his 
own estimate of the work, whether favourable or otherwise. That its formulae 
and processes represent Pharmacy up to the present time, few, after the severe 
criticism it has undergone, will be bold enough to assert; but, in justice, I 
think it must be conceded as a whole to be a decided improvement on the 
London edition ; and as soon as we have recovered from the unpleasant inter¬ 
ference with our ordinary processes, the unprivileged trespass on custom, the 
never-welcome call to sudden progress, it will not then be considered the hire¬ 
ling it now seems. 
Still, taking this most charitable view of its teachings, I think, among others, 
the vague process given for making Unguentum Hydrargyri Nitratis one that 
will admit of some improvement. We are directed “to melt the lard in the 
oil by a steam or water-bath . . . and while the mixture is hot add the solution 
of mercury, also hot.” It might also have been further added—and your result 
will be a most uncertain one ; for, supposing the temperature of hot to be, say 
200° F., or upwards, which is perfectly natural, seeing that it is readily obtain¬ 
able by a steam or water-bath, and your acid to have a sp. gr. of 1*5, the action 
would take place so violently on mixing, as to be perfectly uncontrollable, and 
the heat generated sufficiently great (together with the action of a strong acid), 
to partially carbonize the fats, and form an ointment granulated, and chocolate- 
coloured ; this would even be the case at some 20° less than the temperature 
above indicated, although not to the same extent. It will also vary in colour 
or consistence, with every considerable variation of the heat employed lower than 
this, thereby showing the necessity of an arbitrary standard if the result is to 
be uniform. 
The directions of the London Pharmacopoeia were not by any means more 
explicit, but the acid there ordered being considerably weaker (and supposing it 
to have a composition of NO s HO-f-3 HO, the acid of sp. gr. 1-42 sufficiently 
strong to effectually peroxidize, and to form an acid solution of the mercury), 
was much more manageable in its action than the present powerful preparation. 
If, on the other hand, too little heat have been used, either the ointment 
will become so hard in a short time as to be useless, or will have a dirty-green 
colour, not at all like the beautiful citron of a nicely-made ointment; these 
latter results have, however, been effectually guarded against in the British 
Pharmacopoeia, by ordering heat to be applied till the mixture froths up, if 
it does not when the solutions are first put together. Here, again, if operating 
on large quantities, great caution will be necessary,'—to remove the vessel from 
the source of heat immediately the slightest effervescence commences, to stir 
vigorously, and should the action be taking place with too much violence, to 
moderate it by floating the dish on cold water, or the before-named denials to 
a good product will be here repeated. So, it will be seen, some trouble and 
care is required to ensure anything like a satisfactory ointment; and no matter 
what particular method of procedure be followed in manipulating with such a 
strong acid, the greatest caution and observance will always be necessary. 
