The Handbook of Soap Manufacture | Page 8

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° 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°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°,
and erucic acid gives brassic acid, melting at 60°C. This reaction also
occurs with the neutral glycerides of these acids, olein being converted
into elaidin, which melts at 32°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. Linolic Series:--
-------------------------------------------------------------------------- Acid. |
Formula. | Melting | Found in | | Point, | | | °C. |
--------------------------------------------------------------------------
Elæomargaric | C{16}H{29}COOH | ... | Chinese-wood oil.
--------------------------------------------------------------------------
Elæostearic | C{16}H{29}COOH | 71 | Chinese-wood oil.
-------------------------------------------------------------------------- Linolic |
C{17}H{31}COOH | Fluid | Linseed, cotton-seed and | | | maize oils.
-------------------------------------------------------------------------- Tariric |
C{17}H{31}COOH | 50.5 | Tariri-seed oil.
-------------------------------------------------------------------------- Telfairic
| C{17}H{31}COOH | Fluid | Telfairia oil.
--------------------------------------------------------------------------
These acids readily combine with bromine, iodine, or oxygen. They are
unaffected by nitrous acid, and their lead salts are soluble in ether.
IV. Linolenic Series:--
-------------------------------------------------------------------- Acid. |
Formula. | Found in

-------------------------------------------------------------------- Linolenic |
C{17}H{29}COOH | Linseed oil.
-------------------------------------------------------------------- Isolinolenic |
C{17}H{29}COOH | Linseed oil.
-------------------------------------------------------------------- Jecoric |
C{17}H{29}COOH | Cod-liver and marine animal oils.
--------------------------------------------------------------------
These acids are similar in properties to those of Class III., but combine
with six atoms of bromine or iodine, whereas the latter combine with
only four atoms.
V. Ricinoleic Series:--
----------------------------------------------------------- | | | | | | Acid. |
Formula. | Melting | Found in | | | | Point, | | | | | °C. | |
|------------|----------------------|---------|-------------| | | | | | | Ricinoleic |
C{17}H{22}(OH)COOH | 4-5 | Castor oil. |
-----------------------------------------------------------
This acid combines with two atoms of bromine or iodine, and is
converted by nitrous acid into the isomeric ricinelaidic acid, which
melts at 52°-53° C. Pure ricinoleic acid, obtained from castor oil, is
optically active, its rotation being [alpha]{d} +6° 25'.
Hydrolysis or Saponification of Oils and Fats.--The decomposition of a
triglyceride, brought about by caustic alkalies in the formation of soap,
though generally represented by the equation already given (pp. 6 and
7)--
C{3}H{5}(OR) + 3NaOH = C{3}H{5}(OH){3} + 3RONa,
is not by any means such a simple reaction.
In the first place, though in this equation no water appears, the
presence of the latter is found to be indispensable for saponification to
take place; in fact, the water must be regarded as actually
decomposing the oil or fat, caustic soda or potash merely acting as a

catalytic agent. Further, since in the glycerides there are three acid
radicles to be separated from glycerol, their saponification can be
supposed to take place in three successive stages, which are the
converse of the formation of mono- and diglycerides in the synthesis of
triglycerides from fatty acids and glycerine. Thus, the above equation
may be regarded as a summary of the following three:--
| OR | OH (i.) C{3}H{5} | OR + NaOH = C{3}H{5} | OR + RONa
|OR |OR | OH | OH (ii.) C{3}H{5} | OR + NaOH = C{3}H{5} | OR +
RONa |OR |OH | OH