473 
vegetable and animal substances. 
the fallacy occasioned by the hygrometric water of the per- 
oxide of copper. It is likely that some slight modification 
may require to be made in my tabular proportion of the con- 
stituents, for I did not resume the subject of indigo, after I 
had become most familiar with the manipulations. 
Camphor is very nearly represented by 
Carbon 10 atoms . . 7.5 . . 78.02 
Hydrogen 9 . . 1.125 . 11.58 
Oxygen 1 . . 1.0 . . 10.40 
9.625 100,00 
or 9 atoms olefiant gas 1 atom carbonic oxide. Naphtha- 
line is, in my opinion, a solid bi-carburet of hydrogen, con- 
sisting of 
Carbon 2 atoms . .1.5 . . 92.9 
Hydrogen 1 . . .0.125 • • 7-i 
1.625 100.0 
It is very difficult, even by the best regulated ignition, to 
resolve the whole carbon of this very volatile body into car- 
bonic acid ; hence, the carbon may come to be underrated 
in the result. Naphthaline is obtained during the rectifica- 
tion of the petroleum of the coal gas works. It is found 
encrusting the pipes in the form of a greyish crystalline 
mass ; and when purified by a second sublimation at the tem- 
perature of about 220 0 , it forms beautiful thin plates, white 
and glistening. It has a powerful petroleum odour. With 
brine of the specific gravity 1.048, these plates, when once 
thoroughly wetted (which is difficult to effect) remain in 
equilibrium ; that is, float in any part of the liquid. That 
number, therefore, represents the specific gravity of naph- 
thaline. It is insoluble in water, but very soluble in ether, 
and moderately so in alcohol. With iodine, it fuses at a gentle 
mdcccxxii. 3 P 
