ON THE SUBLIMATION OF THE ALKALOIDS. 
59 
immediate effect upon it. It will very rarely, if ever, be necessary to use a 
higher power. 
The chemical appliances are, as I have already indicated, of the simplest kind. 
A spirit-lamp, a few crucible covers and glass cells, some disks of common 
window-glass, a few drop-bottles to contain solutions of definite strength, a few 
watch-glasses, and (as being more convenient than the glass rod) a pointed 
triangular piece of window-glass mounted in a wooden handle, make up the sum 
of necessary apparatus. 
The white surface of porcelain being visible through the glass disk, as through 
a window, the behaviour of the substance under examination is easy to observe. 
It may be driven off without undergoing change or leaving residue, and the 
disk may be covered with crystals, as happens with arsenious acid, or with an 
amorphous sublimate, as happens with calomel; it may coalesce, throw out long 
silky crystals, to be gradually transferred as crystals to the glass disk, as is the 
case with corrosive sublimate; and it may melt, with or without previous 
change of colour, retain or shift its place, deposit carbon more or less abun¬ 
dantly, and yield a sublimate of detached crystals (veratrine), twigs (solanine), 
tufts (meconine), branching patterns (s rychnine, morphine, cryptopia, etc.), 
watered patterns with or without crystalloids (several alkaloids and glucosides), 
the melting and deposit of carbon being common properties of the alkaloids and 
of some analogous active principles. Of these several will be found to yield 
sublimates, both before and after melting. This happens both with canthari- 
dine aud strychnine. Corrosive sublimate, when the heat is quickly applied and 
is stronger than necessary, melts before subliming; when more slowly and cauti¬ 
ously, in the manner above stated. 
These changes of form and colour, and many others taking place in sub¬ 
stances not at present supposed to furnish sublimates, may be readily traced on 
the white surface of porcelain, and may be made to contribute in no slight 
degree to the work of diagnosis. 
'the microscopic examination of the sublimate follows next in order; and 
affords, as might be anticipated, very valuable aid in distinguishing one sub¬ 
stance from another. 
Then follows, as the last step in this mixed method, the actions of reagents 
on the sublimates, both immediate or speedy, as seen under the microscope, and 
remote, as exhibited in the dry spot, which, in its turn, is examined by the 
microscope, and, if need be, mounted for future use and reference. 
Of this combination of tests, in which simple but delicate chemical processes 
are made to go hand-in-hand with the use of the microscope,—of this union of 
micro-chemistry with microscopy, it may be safely predicted that it will prove 
extremely fruitful in practical results. Each part of the threefold procedure, 
the heating and sublimation, the microscopic examination of the sublimate, and 
the application to it of appropriate liquid reagents, furnishes its own special ele¬ 
ment towards a combination which can hardly fail of being distinctive. 
In examining, as I propose now to do, the precautions which we must observe 
if we would turn to practical account this newly discovered property of the 
alkaloids, I shall consider in their turn,—1, the application of heat; 2, the 
examination and disposal of the sublimate; and 3, the choice, use, and value of 
reagents. 
1. The principal precaution to be observed in the application of heat is, that 
it should be moderate and gradual. It is best to act on the assumption that the 
substance under examination may be one of a considerable group of bodies, 
some of which sublime at very moderate temperatures. The spirit-lamp should, 
therefore, be placed at first three or four inches below the slab of porcelain, so 
that the point of its flame may not touch it; and if, under this low temperature, 
the disk of glass is not dimmed, the lamp should be raised by degrees till the 
