leic acid with 1 per
cent. of iodine in autoclaves up to 270 deg.-280 deg. C., about 70 per cent. is
converted into stearic acid, and Zuerer has devised (German Patent
62,407) a process whereby the oleic acid is first converted by the
action of chlorine into the dichloride, which is then reduced with
nascent hydrogen. More recently Norman has secured a patent (English
Patent 1,515, 1903) for the conversion of unsaturated fatty acids of
Series II. into the saturated compounds of Series I., by reduction with
hydrogen or water-gas in the presence of finely divided nickel, cobalt
or iron. It is claimed that by this method oleic acid is completely
transformed into stearic acid, and that the melting point of tallow
fatty acids is raised thereby about 12 deg. C.

Another method which has been proposed is to run the liquid olein over
a series of electrically charged plates, which effects its reduction to
stearin.

Stearic acid is also formed by treating oleic acid with fuming hydriodic
acid in the presence of phosphorus, while other solid acids are obtained
by the action of sulphuric acid or zinc chloride on oleic acid.

Acids of Series II. may also be converted into saturated acids by
heating to 300 deg.C. with solid caustic potash, which decomposes them into
acids of the stearic series with liberation of hydrogen. This reaction,
with oleic acid, for example, is generally represented by the equation--

C_{18}H_{34}O_{2} + 2KOH = KC_{2}H_{3}O_{2} + KC_{16}H_{31}O_{2} + H_{2},

though it must be really more complex than this indicates, for, as Edmed
has pointed out, oxalic acid is also formed in considerable quantity.
The process on a commercial scale has now been abandoned.

One of the most important properties of this group of acids is the
formation of isomeric acids of higher melting point on treatment with
nitrous acid, generally termed the _elaidin reaction_. Oleic acid, for
example, acted upon by nitrous acid, yields elaidic acid, melting at
45 deg., and erucic acid gives brassic acid, melting at 60 deg.C. This reaction
also occurs with the neutral glycerides of these acids, olein being
converted into elaidin, which melts at 32 deg.C.

The lead salts of the acids of this series are much more soluble in
ether, and the lithium salts more soluble in alcohol than those of the
stearic series, upon both of which properties processes have been based
for the separation of the solid from the liquid fatty acids.

III. _Lin