Page 10 - ALLEN'S COMMERCIAL ORGANIC ANALYSIS A TREATISE ON THE PROPERTIES, MODES OF ASSAYING... VOL II

CONSTITUTION AND CHEMICAL PROPERTIES. 1
oils (q. v). Palm oil is bleached by hot air in a similar fashion. Of
chemical oxidising reagents mention may be made of dichromate and
mineral acid (used in the purification of palm oil), manganese dioxide
and hydrochloric acid, and hydrogen peroxide. Wax bleached by
chlorine is apt to contain chlorine fatty compounds, which are de-
• composed with the liberation of hydrochloric acid when the wax is
subsequently burnt in the form of candles.
Chemical Precipitants.-Protein impurities in fish oils and other
oils may be chemically precipitated by means of tannin or solutions of
metallic salts capable of combining with them.
For details of these and similar methods of clarifying, bleaching, and
deodorising oils see Alder Wright and Mitchell's, Oils, Fats, and Waxes,
1903, 310.
Purification by Pressure.-Hydraulic pressure is widely em-
ployed for separating the solid from the liquid constituents of oils.
The solid fats thus separated are commercially known as "stearin,"
though, as a rule, they are far from approximating in composition to the
triglyceride of stearic acid. Similarly, the liquid expressed oils are
conveniently termed "oleins," though of very complex composition.
The following are some of the chief instances in which commercial fats
and oils are separated by pressure into solid and liquid portions.

Original oil Liquid product Solid product

Olive oil. Purified olive oil. Olive oil stearin.
Cottonseed oil, Purified cotton oil. Cotton oil stearin,
Coconut oil. Coconut olein. Coconut stearin.
Tallow. Tallow oil. Tallow stearin.
Lard. Lard oil. Lard stearin,
Whale oil. Purified whale oil. Whale stearin.
Sperm oil. Purified sperm oil. Spermaceti.

CONSTITUTION AND CHEMICAL PROPERTIES OF FATS,
OILS, AND WAXES.
The fats, fixed oils, and waxes are esters of a series of acids mostly
monobasic and called, from their sources, the fatty acids. The natural
fats and fixed oils are all esters of the triad radicle, .CH,.CH.CH,.
Their composition may be expressed by the general formula C,HA,,
in which A is a radicle of some acid. From the fact that the radicle