372 
MR. JOHNSTON ON THE CONSTITUTION OF THE RESINS. 
5. and 6.). We are to suppose, therefore, that, whether they actually existed as such 
in the resin or were formed by the action of the alkali, an additional quantity of 
benzoic acid and water was removed from the resin by the carbonate of potash. 
With this, the formulae deduced from analyses 4, 5 and 6 agree, being respectively 
C 4 q H -24 ^95 and C 4 q H 24 Og. Thus 
C 40 H 24 Og gives 
Found by analysis 4. 
c 40 H l24 O k gives 
Found by analyses 5 and 6. 
Carbon 71 *82 
71*95 
73*55 
72*59 
73*13 
Hydrogen 7'03 
7*16 
7*25 
7*45 
7- 53 
Oxygen 21*15 
20*89 
19*20 
19*96 
19*34 
100 
100 
100 
100 
100 
Without laying much stress at present on the first of these formulae, we may from 
the above analyses conclude, that the benzoin of commerce, and after partial heating 
and boiling in water, is of very variable composition, but that after boiling in con- 
centrated solutions of the carbonated alkalies and carefully heating, its constitution 
may be represented very approximately by C 40 H 24 O g . This conclusion is confirmed 
by the examination of the resin which remains after the crude benzoin is boiled 
with quicklime. 
II. Action of Caustic Lime on Resin of Benzoin. 
When the benzoin resin of commerce is intimately mixed with quicklime and boiled 
in a large quantity of water, the resin unites with the lime, and forms a nearly inso- 
luble compound of a beautiful purple colour, while benzoate of lime is also produced 
and dissolved by the boiling water. Thrown on the filter and washed for a length 
of time, the washings pass through of a yellow colour, which diminishes little in in- 
tensity, and is due chiefly to the solubility of the compound of a peculiar resin with 
the lime. I have subjected three successive portions of the crude resin to this treat- 
ment, and though I place most reliance on the results of the last portion, I insert 
the analyses of the other portions, as they are not without interest, in connexion both 
with the nature of the resin itself, and the precautions necessary to be adopted in 
order to obtain it of constant composition. 
1. After boiling with quicklime and washing with boiling water, the purple com- 
pound was decomposed by boiling with dilute muriatic acid, and afterwards with 
water. It was then dried at 212° Fahr., treated with cold alcohol, and the solution 
evaporated at 212° Fahr. The resin was of a reddish-brown colour, and left 07 per 
cent, of ash. 
8*48 grs. (8*42 grs. pure resin) gave C = 21*61, and H = 5*595 grs. 
2. The second portion similarly treated gave a similar resin, which left, when burned 
in the air, 0*69 per cent, of ash, and of which when heated long at 212° Fahr. 
A. 8 00 grs. (7*945 grs. pure resin) gave C = 20*47, and H = 5*176 grs. 
B. Heated four days longer at 180° Fahr., 8*96 grs. (8*898 grs. pure resin) gave 
C = 23*21, and H = 5*61 grs. 
