ing equation:

KHC_{4}H_{4}O_{6} + NaHCO_{3} = KNaC_{4}H_{4}O_{6} + H_{2}O +
CO_{2}.

The carbon dioxide evolved escapes through the dough, thus
making it light and porous.

~Citric acid~ (H_{3}.C_{6}H_{5}O_{7}). This acid occurs in many fruits,
especially in lemons. It is a white solid, soluble in water, and is
often used as a substitute for lemons in making lemonade.

~Lactic acid~ (H.C_{3}H_{5}O_{3}). This is a liquid which is formed in the
souring of milk.

~Oleic acid~ (H.C_{18}H_{33}O_{2}). The derivatives of this acid
constitute the principal part of many oils and liquid fats. The acid
itself is an oily liquid.

ETHEREAL SALTS

When acids are brought in contact with alcohols under certain conditions
a reaction takes place similar to that which takes place between acids
and bases. The following equations will serve as illustrations:

KOH + HNO_{3} = KNO_{3} + H_{2}O,

CH_{3}OH + HNO_{3} = CH_{3}NO_{3} + H_{2}O.

The resulting compounds of which methyl nitrate (CH_{3}NO_{3}) may be
taken as the type belong to the class known as _ethereal salts_, the
name having been given them because some of them possess pleasant
ethereal odors. It will be seen that the ethereal salts differ from
ordinary salts in that they contain a hydrocarbon radical, such as
CH_{3}, C_{2}H_{5}, C_{3}H_{5}, in place of a metal.

~The nitrates of glycerin~ (_nitroglycerin_). Nitric acid reacts with
glycerin in the same way that it reacts with a base containing three
hydroxyl groups such as Fe(OH)_{3}:

Fe(OH)_{3} + 3HNO_{3} = Fe(NO_{3})_{3} + 3H_{2}O,

C_{3}H_{5}(OH)_{3} + 3HNO_{3} = C_{3}H_{5}(NO_{3})_{3} + 3H_{2}O.

The resulting nitrate (C_{3}H_{5}(NO_{3})_{3}) is the main constituent
of _nitroglycerin_, a slightly yellowish oil characterized by its
explosive properties. Dynamite consists of porous earth which has
absorbed nitroglycerin, and its strength depends on the amount present.
It is used much more largely than nitroglycerin itself, since it does
not explode so readily by concussion and hence can be transported with
safety.

~The fats.~ These are largely mixtures of the ethereal salts known
respectively as olein, palmitin, and stearin. These salts may be
regarded as derived from oleic, palmitic, and stearic acids
respectively, by replacing the hydrogen of the acid with the glycerin
radical C_{3}H_{5}. Since this radical is trivalent and oleic, palmitic,
and stearic acids contain