378 
MR. JOHNSTON ON THE CONSTITUTION OF THE RESINS. 
C 40 H 30 , should be given oft", that is, a compound in which the elements are in the 
ratio of 4 to 3. Can the naphthoid fluid observed to pass off be such a compound ? 
That which is volatilized when the supposed resin C 40 H 24 0 9 is heated, cannot be 
of the same constitution, since the result is to increase the per centage of carbon, not 
to diminish it, as in the present case. (See analyses 7 to 13, and pp. 373 and 374.) 
IV. Action of Oxide of Lead on Resin of Benzoin. 
When a solution of acetate of lead in alcohol is poured into a similar solution 
of the resin of benzoin of commerce, a precipitate appears in comparatively inconsi- 
derable quantity ; and though both oxide of lead and resin be largely present, no 
further precipitate falls, unless fresh portions of the resinous solution be added. 
This remark applies to the greater number of the resins belonging to our second 
group (C 40 H 24±s O y ). On the addition of caustic ammonia, however, a second and 
more copious precipitate is obtained. 
1 . The precipitate which falls on the admixture of the two solutions. 
A portion of this salt being well washed, and afterwards dried at 250° Fahr., was 
subjected to analysis. 
A. 6*10 grs. left T455 of oxide of lead, or 23*85 per cent. ; and 1 2*9 1 grs. gave 
C = 25*42, and H = 5*89 grs. 
B. 4*625 grs. left 1*15 of oxide of lead, or 24*86 per cent.; and 10*535 grs. gave 
C = 20*68 grs., and H = 4*725 grs. 
These results are equal to 
A (23). 
B (24). 
Carbon 54*45 
54*28 
40 atoms. 
Hydrogen 5*07 
4*99 
22*4 atoms. 
Oxygen 16*63 
15*87 
8*91 atoms. 
Oxide of lead 23*85 
24*86 
1*05 atoms. 
100 
100 
The formula Pb O + C 40 H 22 0 9 , gives 
Per cent. 
Carbon 
3057-480 
54*34 
Hydrogen 
274*549 
4*88 
Oxygen 
900*000 
16*10 
Oxide of lead 
1394*498 
24*78 
5626*527 
100 
These calculated numbers agree vei 
ry closely with those found by 
would seem to justify us in adopting C 40 H 22 0 9 , as the formula for the resin contained 
in this salt*. This, it will be observed, is also the formula for the resin precipitated, 
though in larger quantity, from the crude benzoin by caustic potash, and of which 
* It is scarcely necessary to remark, that, if the resin employed contain any free benzoic acid, the precipitate 
here analysed would be mixed with benzoate of lead. 
