340 ODOROGRAPHIA. 
with the crude camphor to allow of a more uniform escape of 
vapour, and thus save “ bumping” or the sudden evolution of con- 
fined volumes of vapour. During the operation the temperature 
must be maintained uniformly at the point of volatilization. The 
process requires great care, for in addition to the very inflammable 
nature of the vapour, if too much heat be applied, the sublimate 
would re-melt and fall back again to the bottom of the flask; and 
if the heat be not great enough the camphor sublimes in loose 
flakes instead of a compact cake. After breaking the flasks, the 
giass fragments have to be carefully separated by hand from the 
adhering camphor. 
Another process consists in subliming the camphor mixed with 
the other ingredients in any convenient vessel furnished with a 
large and well-cooled receiver and re-melting the product in close 
vessels under pressure, cooling the liquid mass as rapidly as pos- 
sible. In this case the operation cannot be so conveniently watched, 
involving a difficulty in regulating the heat, and the condenser 
must be made of some material not subject to rust in order that 
the product may not be contaminated. 
Camphor forms a white, tough, semi-crystalline solid mass which 
can only be powdered when moistened with alcohol or some other 
solvent. It dissolves in 1300 parts of water at 20° C., and at 
12° C. in 0°8 part of alcohol of sp. gr. 0°806. It is readily soluble 
in ether, acetone, chloroform, benzene, and other hydrocarbons, 
also in glacial acetic acid and in carbon disulphide. It melts at 
175° C., and boils at 204° C., but volatilizes very rapidly at the 
ordinary temperature, and sublimes when kept in close vessels in 
lustrous hexagonal crystals which frequently form splendid stars. 
A fragment of pure camphor placed on a heated spoon or ina 
warm situation will wholly disappear, and if the sample be quite 
pure the evolved fumes are fragrant and quite free from acid or 
terebinthinate odour. As a test distinguishing natural camphor 
‘from artificial camphor,—ammonia gives but a slight precipitate 
in an alcoholic solution of natural camphor, and this precipitate is 
dissolved on shaking the mixture; a similar solution of artificial 
camphor under the like treatment gives a flocculent precipitate 
which remains undissolved. Another distinguishing test is the 
application of polarized light :—If small fragments of natural and 
artificial camphor be placed separately on glass slides, and a drop 
of alcohol added to each, they dissolve and speedily re-crystallize. 
