The Handbook of Soap Manufacture | Page 7

the "fatty acids" or rather those

insoluble in water, acids like acetic, propionic, butyric, caproic,
caprylic and capric, which are all more or less readily soluble in water,
remaining for the most part dissolved in the aqueous portion. All the
acids naturally present in oils and fats, whether free or combined, are
monobasic in character, that is to say, contain only one
carboxyl--CO.OH group. The more important fatty acids may be
classified according to their chemical constitution into five homologous
series, having the general formulæ:--
I. Stearic series C{n}H{2n+1}COOH II. Oleic series
C{n}H{2n-1}COOH III. Linolic series C{n}H{2n-3}COOH IV.
Linolenic series C{n}H{2n-5}COOH V. Ricinoleic series
C{n}H{2n-7}COOH
I. Stearic Series.--The principal acids of this series, together with their
melting points and chief sources, are given in the following table:--
------------------------------------------------------------------------------- Acid.
| Formula. | Melting | Found in | | Point, | | | °C. |
-------------------------------------------------------------------------------
Acetic | CH{3}COOH | 17 | Macassar oil.
------------------------------------------------------------------------------
Butyric | C{3}H{7}COOH | ... | Butter, Macassar oil.
------------------------------------------------------------------------------
Isovaleric | C{4}H{9}COOH | ... | Porpoise and dolphin oils.
------------------------------------------------------------------------------
Caproic | C{5}H{11}COOH | ... | Butter, cocoa-nut oil.
------------------------------------------------------------------------------
Caprylic | C{7}H{15}COOH | 15 | Butter, cocoa-nut oil, | | | Limburg
cheese.
------------------------------------------------------------------------------
Capric | C{9}H{19}COOH | 30 | Butter, cocoa-nut oil.
------------------------------------------------------------------------------
Lauric | C{11}H{23}COOH | 44 | Cocoa-nut oil, palm-kernel oil.
------------------------------------------------------------------------------
Ficocerylic | C{12}H{25}COOH | ... | Pisang wax.
------------------------------------------------------------------------------

Myristic | C{13}H{27}COOH | 54 | Nutmeg butter, liver fat, | | |
cocoa-nut oil, dika fat, | | | croton oil.
------------------------------------------------------------------------------
Palmitic | C{15}H{31}COOH | 62.5 | Palm oil, most animal fats.
------------------------------------------------------------------------------
Daturic | C{16}H{33}COOH | | Oil of Datura Stramonium.
------------------------------------------------------------------------------
Stearic | C{17}H{35}COOH | 69 | Tallow, lard, most solid | | | animal
fats. ------------------------------------------------------------------------------
Arachidic | C{19}H{39}COOH | 75 | Arachis or earth-nut oil, | | | rape
and mustard-seed oils.
------------------------------------------------------------------------------
Behenic | C{21}H{43}COOH | ... | Ben oil, black mustard-seed | | | oil,
rape oil.
------------------------------------------------------------------------------
Lignoceric | C{23}H{47}COOH | 80.5 | Arachis oil.
------------------------------------------------------------------------------
Carnaubic | C{23}H{47}COOH | ... | Carnauba wax.
------------------------------------------------------------------------------
Pisangcerylic | C{23}H{47}COOH | ... | Pisang wax.
------------------------------------------------------------------------------
Hyænic | C{24}H{49}COOH | ... | Hyæna fat.
------------------------------------------------------------------------------
Cerotic | C{25}H{51}COOH | 78 | Beeswax, China wax, spermaceti.
------------------------------------------------------------------------------
Melissic | C{29}H{59}COOH | 89 | Beeswax.
------------------------------------------------------------------------------
Psyllostearylic| C{32}H{65}COOH | ... | Psylla wax.
------------------------------------------------------------------------------
Theobromic | C{63}H{127}COOH | ... | Cacao butter
------------------------------------------------------------------------------
Medullic and margaric acids, which were formerly included in this
series, have now been shown to consist of mixtures of stearic and
palmitic, and stearic palmitic and oleic acids respectively.
The acids of this group are saturated compounds, and will not combine

directly with iodine or bromine. The two first are liquid at ordinary
temperatures, distil without decomposition, and are miscible with water
in all proportions; the next four are more or less soluble in water and
distil unchanged in the presence of water, as does also lauric acid,
which is almost insoluble in cold water, and only slightly dissolved by
boiling water. The higher acids of the series are solid, and are
completely insoluble in water. All these acids are soluble in warm
alcohol, and on being heated with solid caustic alkali undergo no
change.
II. Oleic Series:--
-------------------------------------------------------------------------- Acid. |
Formula. | Melting | Found in | | Point, | | | °C. |
-------------------------------------------------------------------------- Tiglic |
C{4}H{7}COOH | 64.5 | Croton oil.
-------------------------------------------------------------------------- Moringic
| C{14}H{27}COOH | 0 | Ben oil.
--------------------------------------------------------------------------
Physetoleic | C{15}H{29}COOH | 30 | Sperm oil.
--------------------------------------------------------------------------
Hypogæic | C{15}H{29}COOH | 33 | Arachis and maize oils.
-------------------------------------------------------------------------- Oleic |
C{17}H{33}COOH | 14 | Most oils and fats.
-------------------------------------------------------------------------- Rapic |
C{17}H{33}COOH | ... | Rape oil.
-------------------------------------------------------------------------- Doeglic |
C{18}H{35}COOH | ... | Bottle-nose oil.
-------------------------------------------------------------------------- Erucic |
C{21}H{41}COOH | 34 | Mustard oils, marine animal | | | oils, rape
oil. --------------------------------------------------------------------------
The unsaturated nature of these acids renders their behaviour with
various reagents entirely different from that of the preceding series.
Thus, they readily combine with bromine or iodine to form addition
compounds, and the lower members of the series are at once reduced,
on treatment with sodium amalgam in alkaline solution, to the

corresponding saturated acids of Series I. Unfortunately, this reaction
does not apply to the higher acids such as oleic acid, but as the
conversion of the latter into solid acids is a matter of some technical
importance from the point of view of the candle-maker, a number of
attempts have been made to effect this by other methods.
De Wilde and Reychler have shown that by heating oleic acid with 1
per cent. of iodine in autoclaves up to 270°-280° C., about 70 per cent.
is converted into stearic acid, and Zürer has devised (German Patent
62,407) a process whereby the oleic acid is first converted by the
action of chlorine into