ON MICRO-SUBLIMATION. 
413 
mix with powdered glass, and to sublime from a flat surface on to a shallow 
watch-glass. This answers much better than double watch-glasses; but the 
process is very precarious and tedious, and the sublimate is generally contami¬ 
nated with coloured matter. 
Sublimates of metallic compounds call for little remark. When sublimed 
under similar conditions, they present for the most part the same features as 
organic sublimates. This is especially noticeable in biniodide of mercury, 
which often forms the secondary sublimate of thin platy crystals, attached by a 
single angle to the glass. 
Strychnine is described in Gmelin’s ‘ Chemistry’ as giving, when heated, an 
opaque white deposit of sublimed strychnine, which appears under a magnifying 
power of 80 diameters to consist of round sharp granules. 
A crystalline sublimate was, I believe, first obtained by Dr. Guy. To obtain 
a sublimate from strychnine a quarter of a grain was mixed with 5 or 6 times 
its bulk of powdered glass, and a small portion of this mixture submitted to 
heat in the manner described for arsenious acid. A slide made warm was placed 
over it, and the whole left until the sublimed crystals appeared of sufficient size. 
If the crystals were small, the slide was returned to its place ; but if they were 
crusted or otherwise unsatisfactory, a fresh slide (of course made warm) was 
commenced. By this means very perfect and typical crystals were obtained. 
Strychnine appear- to sublime within a few degrees of the heat at which it 
commences to change colour and decompose, as with very careful treatment 
the mixture of glass and strychnine turns brown and the sublimate sometimes 
appears slightly coloured. When heated to decomposition, strychnine emits a 
most suffocating odour, resembling the smell of asphalte. By operating upon 
larger quantities of strychnine, half a grain of sublimate was obtained, and 
upon submitting this to the usual tests, the characteristic reactions of strychnine 
resulted. 
Salicin .—I have been unable to find any allusion to the sublimation of this 
substance. It sublimes with comparative ease in needles, small plates, and 
other forms. If the process is continued for an hour and a half or two hours 
(being carefully watched that the receiving-glass does not become hot enough 
to fuse the sublimate), there will be found the secondary sublimate in thin 
plates before mentioned. 
Santonin. —Gmelin’s ‘Chemistry’ has the following:—“Santonin heated a 
little above the melting-point turns brown, gives off yellowish vapours which 
flow back, condense to a yellow transparent resin, while the residue becomes car¬ 
bonized.” Gerhardt says, “ It may be sublimed, but the sublimation is only 
successful in small quantities; when we operate with more matter it is decom¬ 
posed, yielding an oil which, on cooling, is brown and resinous.” When sub¬ 
mitted to heat in the manner described, it sublimes readily and in regular 
crystals. If the process is long continued, the secondary sublimate makes its 
appearance, but by careful manipulation solid crystals may be obtained of con¬ 
siderable size. 
All the cinchona alkaloids yield sublimates which possess little, if any, simi¬ 
larity. 
Quinine .—In Gmelin’s ‘ Chemistry ’ it is stated, “ that when hydrate of qui¬ 
nine is heatefd for a long time in the air, a portion of it sublimes in the form of 
a yellow powder.” By careful manipulation, quinine yields a crystalline subli¬ 
mate. About the tenth of a grain of quinine was mixed with four or five times 
its bulk of powdered glass, and heated in the usual way. The first sublimate 
was obtained at too great a heat, and when removed from the fire appeared as a 
drop of fluid, as it cooled it solidified, and when examined under the micro¬ 
scope it was distinctly crystalline. By more carefully regulating the heat a 
sublimate in very small granules was obtained, this was kept in its place for 
