only one replaceable hydrogen atom to the
molecule, it is evident that three molecules of each acid must enter
into each molecule of the ethereal salt. The formulas for the acids and
the ethereal salts derived from each are as follows:

HC_{18}H_{33}O_{2} (oleic acid)
C_{8}H_{6}(C_{18}H_{33}O_{2})_{3}, (olein)

HC_{16}H_{31}O_{2} (palmitic acid)
C_{3}H_{5}(C_{16}H_{31}0_{2})_{3} (palmitin)

HC_{18}H_{35}O_{2} (stearic acid)
C_{3}H_{5}(C_{18}H_{35}O_{2})_{3} (stearin)

Olein is a liquid and is the main constituent of liquid fats. Palmitin
and stearin are solids.

~Butter fat and oleomargarine.~ Butter fat consists principally of olein,
palmitin, and stearin. The flavor of the fat is due to the presence of a
small amount of butyrin, which is an ethereal salt of butyric acid.
Oleomargarine differs from butter mainly in the fact that a smaller
amount of butyrin is present. It is made from the fats obtained from
cattle and hogs. This fat is churned up with milk, or a small amount of
butter is added, in order to furnish sufficient butyrin to impart the
butter flavor.

~Saponification.~ When an ethereal salt is heated with an alkali a
reaction expressed by the following equation takes place:

C_{2}H_{5}NO_{3} + KOH = C_{2}H_{5}OH + KNO_{3}.

This process is known as _saponification_, since it is the one which
takes place in the manufacture of soaps. The ordinary soaps are made by
heating fats with a solution of sodium hydroxide. The reactions
involved may be illustrated by the following equation representing the
reaction between palmitin and sodium hydroxide:

C_{3}H_{5}(C_{16}H_{31}O_{2})_{3} + 3 NaOH
= 3 NaC_{16}H_{31}O_{2} + C_{3}H_{5}(OH)_{3}.

In accordance with this equation the ethereal salts in the fats are
converted into glycerin and the sodium salts of the corresponding acids.
The sodium salts are separated and constitute the soaps. These salts are
soluble in water. When added to water containing calcium salts the
insoluble calcium palmitate and stearate are precipitated. Magnesium
salts act in a similar way. It is because of these facts that soap is
used up by hard waters.

ETHERS

When ethyl alcohol is heated to 140 deg. with sulphuric acid the reaction
expressed by the following equation takes place:

2C_{2}H_{5}OH = (C_{2}H_{5})_{2}O + H_{2}O.

The resulting compound, (C_{2}H_{5})_{2}O, is ordinary ethe