NOTES ON WHITE PRECIPITATE. 
ki y 
515 
to have specimens of that class renewed from time to time. The specimens got 
completely destroyed, not by very minute insects, but by a species of little 
beetle; and he did not know that any method such as had been suggested would 
prevent the attacks of these little creatures. He was not aware whether their 
museum was infested with them; but at the College of Physicians, where there 
was an extremely old collection of the materia medica, almost all the specimens 
of a certain class were practically worthless, owing to the depredations of these 
little beetles. At the museum in Kew also, much injury was done by these 
beetles. 
In some further remarks that were made, carbolic acid and also camphor were 
recommended, where their smell would not interfere with their use. 
NOTES ON WHITE PRECIPITATE. 
BY PROFESSOR ATTFIELD. 
At the Dundee meeting of the British Pharmaceutical Conference (Sept. 
1867), Mr. J. B. Barnes gave the results of an examination of sixty-one samples 
of “ white precipitate,” fifty-seven of which were found to be quite free from 
non-volatile adulterants, such as dry white-lead and chalk. Three months after¬ 
wards, Mr. Borland, of Kilmarnock, in a communication to the Pharmaceutical 
Society, stated that of twenty-four samples of u white precipitate” he had ex¬ 
amined, not one contained any non-volatile matter, yet only five could be said 
to be the pure infusible official preparation, containing 79^ per cent, of mercury, 
the remaining nineteen being the “ fusible white precipitate” of old Pharmaco¬ 
poeias, and containing only 65^ parts of mercury in 100. The object of the 
present note is to show that, while the property of complete volatility in “ white 
precipitate” does not necessarily imply perfect purity, the character of fusibility 
does not necessarily indicate that the specimen only contains 65| per cent, of 
mercury, or the quality of infusibility prove that it contains the official propor¬ 
tion of 79^ per cent. 
Six specimens of “ white precipitate” were examined in reference to (a) vola¬ 
tility, (6) fusibility, and (c) percentage of mercury. Each specimen, when placed 
in a test-tube and heated, volatilized without leaving a trace of residue. During 
sublimation, four gave no signs of fusion, one partially melted, and one liquefied 
entirely. The percentage of mercury in the samples is given in the following 
table :— 
Commercial u White Precipitate.” 
Number. . Mercury in 100 parts. 
1 . . . volatile . . . infusible.78'59 
2 . . . volatile .. . . infusible .. . . . . 77-87 
3 . . . volatile . . . infusible ..... 76’44 
4 . . . volatile . . . infusible ..... 75-11 
5 . . . volatile . . . partially fusible . . . 73-08 
6 . . . volatile . . . fusible.72-00 
NH 2 HgCl, B. P. 1867 . . infusible .... 79*52 
NH 2 HgCl, HgCl 2 .... partially fusible . . 76-55 
NIl 2 IlgCl,NH 4 Cl, L. P.1824 fusible . .... 65-57 
An inspection of this table will show that neither specimen contains any non¬ 
volatile adulterant, properly so-called,—no plaster of Paris, chalk or dry white- 
lead is present. Secondly, the fact that the first four are infusible, and the 
other two fusible would, up to the present time, have been considered to indicate 
that the former had been made by the modern process of pouring solution of 
corrosive sublimate into solution of ammonia, and contained the normal propor- 
2 N 2 
