ON THE SUBLIMATION OF THE ALKALOIDS. 
61 
in solution. This liability to error is well illustrated by one of my early experi¬ 
ments. I had obtained a thick crust of morphine of the variety to which I pro¬ 
pose to give the title of ‘ smoked and I applied to this a strong, freshly made 
solution of bichromate of potash. This resulted in an instantaneous formation 
of winged crystals of extraordinary size, brilliancy, and beauty. It was natural 
to attribute these to the solution rather than to the solvent; but having occasion 
after a time to institute a methodical examination of the sublimates of morphia, 
and to use distilled water as the first of a series of tests, I found to my surprise, 
but also to my instruction, crystals of the same form and brilliancy, and nearly 
of the same size, forming under the microscope with the same rapidity. It is 
clear, therefore, that in examining the alkaloids and other substances which 
yield sublimates, we must begin by ascertaining the effect of the very simplest 
of reagents, distilled water. 
Now these remarks have a direct practical bearing on the selection of our 
tests. A preference ought to be given to reagents which leave no residue of 
their own : to distilled water, to alcohol, ether, chloroform, benzole, and fusel 
oil; and to acetic acid and the dilute mineral acids. Then those salts should 
be preferred of which the solutions yield dry residues of one or two definite 
forms, not such as put on many different shapes, are deliquescent themselves, 
and are likely to leave moist and unstable compounds. 
Nor is the strength of the solution a matter of little or no importance : for it 
should be borne in mind that the sublimates to which we apply them contain 
very minute fractions of a grain ; and that a very strong solution, after acting 
on this minute quantity, would leave a coarse deposit of its own, both over the 
general surface and at the margin of the spot, which, blending with the reaction, 
would obscure and confuse it. As a general rule, therefore, solutions of mode¬ 
rate strength are to be pieferred, such as 1 grain to 250 of carbazotic acid, and 
1 grain to 100 of bichromate of potash, of the red prussiate of potash, and of 
the nitro-prusside of sodium. 
It is true that, by a simple method of procedure, this inconvenience of strong 
solutions may be obviated,—in all those cases, at least, in which the reagent, either 
immediately or after a short interval, developes in the sublimate characteristic 
crystalline forms. We may watch the process till fresh crystals cease to form, 
then absorb the unexpended reagent by a strip of blotting-paper, drench the 
spot once or twice with distilled water, absorb it in the same way, and so leave 
behind only the crystalline forms due to the reagent and the sublimate. 
I have already more than once intimated my belief that this peculiar union 
of micro-chemistry with the microscope would prove fruitful in discoveries, and 
in my second paper I mentioned some substances, other than the alkaloids and 
volatile metallic poisons, which were found to yield sublimates when heated, 
and among these I specified the animal products, urea, uric acid, hippuric acid, 
alloxan, and uramile. But these results, I must confess, scarcely prepared me 
to expect a sublimate from a blood-stain. Yet, on separating the fibres of a 
small spot of a cotton texture stained with blood about twenty-five years since, 
and submitting a section of the fibre an eighth of an inch long to heat, I ob¬ 
tained a figured pattern of the colour of blood, such as might be caused by a 
solution of blood in some thin oily liquid; and this figured pattern was sur¬ 
rounded by a colourless border having bright figured patterns such as those 
which mark the less characteristic portions of crystalline sublimates. On re¬ 
peating my experiments, I found that the result was constant; and on con¬ 
ducting them with care and under the guidance of my first microscopic exami¬ 
nations, I uniformly obtained two sublimates, the first colourless and apparently 
crystalline, the second, under a higher temperature, of the colour of the blood¬ 
stain from which it was procured, and of the figured pattern of which I have 
just spoken. 
