s these are inodorous, no advantage is gained in
this way, and there is, further, the inconvenience in cold weather of
having to first melt the oil before use.

_Safrol_, an ether which is the chief constituent of sassafras oil, and
also found in considerable quantity in camphor oil. It is sold as an
artificial sassafras oil, and is very much used in perfuming cheap
toilet or household soaps. Its specific gravity at 15 deg. C. is
1.103-1.106; refractive index at 20 deg. C., 1.5373; and it dissolves in
fifteen volumes of 80 per cent. alcohol.

_Santalol_, the alcohol or mixture of alcohols obtained from sandalwood
oil. Its specific gravity at 15 deg. C. is 0.9795; optical rotation, -18 deg.;
and refractive index at 20 deg. C., 1.507.

_Terebene_, a mixture of dipentene and other hydrocarbons prepared from
turpentine oil by treatment with concentrated sulphuric acid, is used
chiefly in medicated soaps. Its specific gravity at 15 deg. C. is
0.862-0.868; the oil is frequently slightly dextro- or laevo-rotatory;
the refractive index at 20 deg. C., 1.470-1.478.

_Terpineol_, an alcohol also prepared from turpentine oil by the action
of sulphuric acid, terpene hydrate being formed as an intermediate
substance. It has a distinctly characteristic lilac odour, and on
account of its cheapness is much used in soap perfumery, especially for
a lilac or lily soap. Its specific gravity at 15 deg. C. is 0.936-0.940;
refractive index at 20 deg. C., 1.4812-1.4835; and boiling point about
210 deg.-212 deg. C. It is optically inactive, and readily soluble in 1.5
volumes of 70 per cent. alcohol.

_Vanillin_, a white crystalline solid, melting at 80 deg.-82 deg. C. and
prepared by the oxidation of isoeugenol. It has a strong characteristic
odour, and occurs, associated with traces of benzoic acid and
heliotropin, in the vanilla bean. It can only be used in small quantity
in light-coloured soaps, as it quickly tends to darken the colour of the
soap.

CHAPTER IX.

GLYCERINE MANUFACTURE AND PURIFICATION.

_Treatment of Lyes--Evaporation to Crude
Glycerine--Distillation--Distilled and Dynamite
Glycerine--Chemically Pure Glycerine--Animal Charcoal for
Decolorisation--Glycerine obtained by other Methods of
Saponification--Yield of Glycerine from Fats and Oils._

As pointed out in Chapter II. the fatty acids, which, combined with soda
or potash, form soap, occur in nature almost invariably in the form of