MR. JOHNSTON ON THE CONSTITUTION OF THE RESINS. 
369 
evaporated separately and much longer heated, when 6*44 grs. 
(6*429 grs, 
gave C = 17*97, and H = 5*715 grs. 
These results give per cent., 
A. 
B. 
C. 
D. 
Carbon 76*57 
76*22 
76*15 
77*29 
Hydrogen 9*98 
10*09 
9*87 
Oxygen 13*45 
13*76 
12*84 
100 
100 
100 
The result of analysis D. agrees 
very closely 
with the formula C 40 H 3 
gives 
Per cent. 
40 Carbon 
= 3057*480 
77*51 
31 Hydrogen 
= 386*867 
9*81 
5 Oxygen 
= 500*000 
12*68 
3944*347 
100 
I consider the portion last analysed (D.) to have been most nearly in the normal 
state, and the result obtained to be the more trustworthy, from the near approxima- 
tion to the calculated numbers above given. It would appear, therefore, that the dif- 
ferent lumps of the natural resin of bdellium, as it is met with in commerce, contain 
the same resinous substance, and that after extraction by alcohol and repeated wash- 
ing with boiling water, this resin requires prolonged heating at a temperature of 200 ° 
Fahr. in the state of a thin film, to free it from water and other volatile matters, and 
bring it to its normal state. 
The formula C 40 H 31 0 5 is that assigned in the third part of these researches* to 
the resin A. of sandarach, which differs from that of bdellium, however, in being a spa- 
ringly soluble resin. Whether these resins be really isomeric, or whether they differ 
by an atom of hydrogen more or less, will be investigated in a future paper. 
The insoluble matter which remains after the natural resin of bdellium is exhausted 
with cold alcohol, consists only of gum, and is taken up by boiling water. 
XXII. Resin of Benzoin. 
The resin of benzoin is one to which considerable interest attaches from its con- 
nexion with benzoic acid, and the numerous series of remarkable compounds, to the 
knowledge of which the study of that acid has led. I commenced the study of it, 
therefore, with the hope, not merely of elucidating its relation to the other resins, but 
also of throwing some light upon that which it bears, or may be expected to bear, to 
the acid so readily obtained from it. In the latter expectation, however, I have for 
the present been in some measure disappointed, in so far at least as I have failed to 
obtain a formula for this resin, by which its rational connexion with the radical ben- 
zyle, and its derivatives, can be, if not satisfactorily comprehended, at least numeri- 
MDCCCXL. 
* Philosophical Transactions, 1839, p. 294. 
3 B 
