ON THE ADULTERATION OF WHITE PRECIPITATE. 
263 
precipitate, because, when heated to about 300° C., it enters into a state of 
fusion before volatilizing. 
The infusible salt does not so behave, but volatilizes without fusing. 
The British Pharmacopoeia of 1864 failed to note this physical property in 
the test then given for this salt, and the same omission is perpetuated in the 
edition of 1867. 
It should have been stated that it is “ entirely volatilized at a heat under red¬ 
ness without fusing.” 
That the fusible salt is still to be met with in commerce, in great measure sup¬ 
plying the place of that which alone ought to be accepted as officinal, I have 
satisfactory reason to know ; as, out of twenty-four samples which I have exa¬ 
mined, not more than five gave evidence of having been prepared according to 
the authorized formula. 
These samples I obtained from different establishments, chiefly in the west of 
Scotland here; and, with the exception of the substitution referred to, not one 
contained any of the non-volatile adulterants met with by Mr. Barnes. 
To show the difference between the two salts, 1 subjoin the formulas for their 
preparation, giving the formula of the London Pharmacopoeia, 1745-1824, and 
the formula of the British Pharmacopoeia, 1867 :— 
Mercurim Prcecipitatus Albus. 
Ph. Lond. 1745. 
Salis Ammoniaci, 
Mercurii Corrosivi Sublimati, 
pondera aequalia. 
Solve siraul in aqua, per chartam cola, et 
solutione salis alicujus alkalini fixi prseci- 
pita ; pulverem praecipitatuin ablue ad 
perfectam dulcedinem. 
So far as I have been able to collate, 
this formula continued to be given in the 
various editions of the London Pharma¬ 
copoeia, without any important change, 
down to 1824, when the precipitant was 
definitively ordered to be subcarbonate of 
potash. 
The product in this case is fusible pre¬ 
cipitate, and is represented by the formula 
NH 3 HgCl, and contains nearly 66 grains 
of mercury in 100 grains of the salt. 
Hydrargyrum Ammoniatum. 
Take of 
Perchloride of Mercury, 3 ounces. 
Solution of Ammonia, 4 fluid ounces. 
Distilled water, 3 pints. 
Dissolve the perchloride of mercury in the 
water with the aid of a moderate heat; 
mix the solution with the ammonia, con¬ 
stantly stirring ; collect the precipitate on 
a filter, and wash it well with cold dis¬ 
tilled water, until the liquid which passes 
through ceases to give a precipitate when 
dropped into a solution of nitrate of silver 
acidulated by nitric acid. Lastly, dry 
the product at a temperature not exceed¬ 
ing 212° F. 
The product here is infusible precipi¬ 
tate, and is represented by the formula 
NH 2 Hg 2 Cl, and contains nearly 80 grains 
of mercury in 100 grains of the salt. 
The motive which induces the manufacturing chemist to employ the old for¬ 
mula in preference to the new becomes at once apparent, when the relative 
proportion of the mercury in the two products is taken into consideration ; and 
this, together with the greater facility and convenience which the first formula 
offers for manufacturing purposes, leads, I have no doubt, to the fusible preci¬ 
pitate being found so widely supplying the place of the officinal salt. 
Fusible precipitate does not seem to me to produce such a beautifully white 
ointment as that made with the infusible; it is more transparent, wanting body 
as painters say, and undoubtedly does not keep so long without becoming yel¬ 
low. I have prepared ointments according to the Pharmacopoeia with both 
varieties, and find that, whilst that made with the fusible salt will become yellow 
in from three to four weeks, that made with the infusible will remain uncoloured 
for at least two months. 
I have not had time to investigate the nature of the change which thus takes 
place in the ointment. Many of the mercurial salts, it is well known, are re¬ 
duced from a higher state of combination to a lower in presence of organic sub- 
