MAGNESIUM : ITS PREPARATION AND PROPERTIES. 
543 
treacle, and might be poured from one vessel to another. The bottom of the basin in 
which it was made was found to be lined with a dark slate-coloured powder, which 
proved to be reduced mercury. In four months after, the ointment had attained the 
consistence of fresh butter in the hot days of summer. 
Thus the process of the British Pharmacopoeia is liable to failure. Prom all the 
experiments I have made, and they have been numerous, and varied according to the in¬ 
structions of the three Colleges, I am led to believe that the degree of chemical action, as 
evidenced by the activity of the effervescence when the ingredients are mixed, is the main 
point to be attended to. If the ingredients be mixed cold, and the temperature main¬ 
tained at a low degree, the ointment will be hard and of a pale yellow hue. If the 
ingredients be mixed very hot, and the temperature allowed to rise with the chemical 
action, the resulting ointment will be brown and too soft. Intermediate temperatures 
wall produce intermediate colours and degrees of hardness, from impracticable solidity to 
absolute liquidity. 
Besides colour and consistence, there is another quality to be attended to. When the 
chemical action has been feeble the ointment produced will be acrid and irritating, as 
well as hard and pale. A portion of this kind of ointment, which to the taste was very 
acrid when newly made, became in a few weeks much less so ; in three months it was 
no longer acrid but metallic in taste. The frequent occurrence of this acridity induced 
surgeons to prescribe the ointment in a state of dilution with lard or other ointments, 
so that it is now almost never otherwise prescribed than diluted. Would it not be 
better to reduce the strength of the ointment in the formula of the Pharmacopoeia to 
one-half, and thus put an end to the necessity of dilu ting it ? The dilute citrine ointment, 
as directed in prescriptions, has no definite meaning as to strength, and the difficulty of 
preparing it is a continual source of annoyance to the apothecary. 
I fear it is impracticable to obtain a citrine ointment which, at its first production, 
shall always present the same appearance and possess the same qualities by any process 
which does not carry into effect the following particulars, viz. the temperature at which 
the mercurial solution and the fatty matters respectively are to be mixed and, by art, 
maintained; the relative quantities of each of the ingredients, and the absolute quantity 
of the whole, which is not to be varied, for much depends on this. Were all this accom¬ 
plished, the ointment would still be liable to subsequent changes, during which its 
medical effects must alter. So that it is probably hopeless to expect an unexceptionable 
process for obtaining a permanent ointment, containing nitrate of mercury in any of its 
forms. It might be supposed that the most prudent way to proceed would be to prepare 
only small quantities at a time; but here again we are met by the possible acridity of 
the new ointment. Dr. Duncan’s process, from which he expected so much, does not 
obviate the difficulties in question. 
A Dublin apothecary, nearly a century ago, acquired great fame for making a citrine 
ointment which remained apparently unchanged during a long time, and was soft from 
the beginning. It was known that the basis was butter. I have tried it, but found it 
acrid for a very long time .—Dublin Medical Press. 
MAGNESIUM: ITS PREPABATION AND PROPERTIES. 
BY EMERSON J. REYNOLDS, F.R.G.S., LECTURER ON PRACTICAL CHEMISTRY, 
LEDWICH SCHOOL OF MEDICINE AND SURGERY, DUBLIN. 
Little more than five years have now elapsed since two distinguished chemists and 
physicists, Professors Bunsen and Roscoe, while engaged in some photo-chemical re¬ 
searches, observed the high refrangibility of the light emitted by burning magnesium- 
wire, and also its great “ actinic ” power; these observations led them to propose it as 
a convenient source of light for photographic purposes. It is but recently that any 
attempt has been made to utilize the valuable hint thus thrown out; this has not been 
due to apathy or neglect, but principally in consequence of the difficulties in the way 
of obtaining the metal in sufficient quantities for commercial purposes. The first steps 
towards the simplification of the manufacture of this metal we owe to the researches 
of Bunsen and Matthiessen ; but to St. Clair Deville and Caron is due the productive 
process at present in use in this country under a patent granted to Mr. Sonstadt, of Man¬ 
chester, a gentleman to whom great praise must be awarded for the energy and perse- 
5 & 2 Q ‘2 
