410 
PHARMACEUTICAL MEETING. 
lias arisen the description of man}’- organic substances, that when heated they 
partly sublime and partly decompose, which, as a scientific statement, is para¬ 
doxical. When a more delicate process was used, better results were obtained. 
In the case of theine, Dr. Stenhouse recommended that it should be obtained 
by sublimation after mixing with sand ; thus rendering it much less liable to be 
destroyed. Theine is now described as wholly sublimable, whereas had it been 
submitted to heat in a glass tube, no doubt the description would have obtained 
that it partly sublimed and partly decomposed. Dr. He!wig’s process of sub¬ 
liming from platinum foil is, I think, equally open to objection. A naked flame 
applied to an alkaloid, with only platinum foil intervening, must afford every 
possibility of the substance being decomposed or destroyed by too great heat; 
the conducting power of platinum being decidedly against its use, and, in con¬ 
sequence of this, Dr. Ilelwig has succeeded in obtaining crystalline sublimates 
in comparatively few instances. 
It would be presumptuous on my part to comment upon the elaborate papers 
of Dr. Guy, and the more so that I have not considered this subject in its rela¬ 
tion to toxicology ; I may, perhaps, be allowed to mention that by more careful 
application of the heat employed, Dr. Guy has been the first to obtain crystal¬ 
line sublimates of many substances. 
The results obtained by the method I have adopted are so at variance with 
much that has been described in various chemical works that they must, if sub¬ 
stantiated, tend in some degree to modify existing ideas on this subject. 
The statement so commonly met with in the descriptions of the behaviour of 
alkaloids when submitted to heat, that they partly sublime and partly decom¬ 
pose, is decidedly opeu to objection. It cannot mean that the sublimation of a 
part is dependent upon the decomposition of a part, and yet it is difficult to put 
any other construction upon it. I suppose it must be admitted, almost as an 
axiomatic principle, that what is true of a part is true of the whole, or, more 
correctly, the properties possessed by a part must also be possessed by the whole ; 
and therefore if a part is capable of sublimation the whole is so too. 
No substance can sublime and decompose at the same temperature: partial 
sublimation and partial decomposition must be owing to the mechanical defect 
of the substance being unequally heated. That the subliming and decomposing 
points of many substances approximate very closely is most probable, as, when 
the heat has been most carefully applied, a sublimate has been contaminated 
with coloured matter, which could only have arisen from decomposition. And 
in many instances the range of temperature at which a substance sublimes is 
very limited; the addition of one or two degrees of heat being quite sufficient 
to decompose it, while the deficiency of one or two degrees prevents auy sub¬ 
limation taking place. Thus in subliming from papaverine, I was unsuccessful 
for eight or ten hours, owing to the temperature being defective or excessive, 
but at another time I obtained a sublimate in as many minutes. 
The statement that a substance sublimes without decomposition is, I think, 
equally objectionable; it is somewhat equivalent to saying, that a substance re¬ 
mains stable without alteration. It may be, and no doubt is expressive, but it is 
hardly correct. Sublimation indicates stability, not decomposition, and, as I 
before remarked, a substance could not undergo both at the same temperature. - 
It may be urged against this that some substances decompose w'hen heated 
into other defiuite compounds, as tannin into metagallic and pyrogallic acids, 
but it would be as correct to say that tannin sublimed with decomposition as to 
say of any other substance that it sublimed without decomposition. 
All sublimates from bodies unchanged by heat should possess the crystalline 
form of the original substance, and iu every case I have not considered a sub¬ 
limate satisfactory unless this result has ensued. Certain conditions are no 
doubt necessary to produce a sublimate in typical crystals, but the statement 
