MR. JOHNSTON ON THE CONSTITUTION OF THE RESINS. 
383 
therefore have been deprived of all the benzoic acid it was capable of yielding ; though 
he states that it had been purified after the method of Unverdorben (see above, ana- 
lyses 4, 5, 6, and 11, 12, 13.). 
General Results in regard to the Resin of Benzoin. 
From the experiments detailed in the present paper it appears probable, 
1. That the colourless resin of benzoin is represented very approximately by the 
formula C 40 h 22 o 9 . 
2. That by the action of heat, of boiling water, or of dilute solutions of the carbo- 
nated alkalies, it is partially decomposed, giving off a volatile oil, a little water and 
benzoic acid, and acquires a composition represented approximately by C 40 H 23 0<„ 
and C 40 H 24 0 9 . 
3. That by the action of concentrated solutions of the carbonated alkalies, at a 
boiling temperature, and of quicklime in boiling water, it is resolved into benzoic 
acid, into one resin, C 40 H 24 0 8 , which does not dissolve, and into another (the resin C. 
of Unverdorben*?) which the salt of lime or of potash dissolves, and which is re- 
presented by C 40 H 30 0 7 . 
4. That caustic potash in like manner decomposes the crude resin, throwing down 
from the alcoholic solution a potash salt, which consists chiefly of a compound of the 
alkali with a resin represented approximately by C 40 H 22 0 9 , but which is of a darker 
colour and is more sparingly soluble than the natural resin, to which the same for- 
mula has been ascribed. The supernatant solution, now of a darker colour, contains 
the second resin, C 40 H 30 0 7 , already obtained by the action of the carbonated alkalies. 
5. That by oxide of lead an analogous change is produced upon the crude resin ; 
the precipitate which falls, on mixing the alcoholic solutions of the resin and of acetate 
of lead, containing by experiment C 40 H 22 O y , and that which is thrown down by the 
subsequent addition of caustic ammonia, a resin C 40 H 26 OjQ-f-. 
6. That all these resins are decomposed more or less easily, giving off volatile mat- 
ters at a temperature much below that at which they melt, and that the results of dif- 
ferent analyses of the same portions of resin are thus liable to be modified to a con- 
siderable extent. 
It was my intention to have included in the present paper some new analyses of the 
resin of dragons blood, already examined in the first part of these researches, and of 
the new resins produced by the action of quicklime and of oxide of lead on the several 
* Thomson’s Organic Chemistry (1838), p. 542. 
t I have not adverted to the apparent difference between this resin and the resin C 40 H 24 0 8 , that namely of 
the elements of two atoms of water only. I am unwilling to adopt the opinion that any of the resins contain 
water as a constituent, till we have some distinct facts on which to rest ; but there can be no difficulty in al- 
lowing that, under certain circumstances, one resin may he transformed into another by assimilating the ele- 
ments of one or more atoms of water. 
