The Handbook of Soap Manufacture | Page 6

spermaceti, consisting chiefly of cetin or cetyl

palmitate, and herein lies the essential difference between fats and
waxes, but as these substances are not soap-making materials, though
sometimes admixed with soap to accomplish some special object, they
do not require further consideration.
The principal pure triglycerides, with their formulæ and chief constants,
are given in the following table:--
[Transcriber's note: Table split to fit on page better.]
--------------------------------------------------------------------- Glyceride. |
Formula. | Chief Occurrence.
--------------------------------------------------------------------- Butyrin |
C{3}H{5}(O.C{4}H{7}O){3} | Butter fat
--------------------------------------------------------------------- Isovalerin |
C{3}H{5}(O.C{5}H{9}O){3} | Porpoise, dolphin
--------------------------------------------------------------------- Caproin |
C{3}H{5}(O.C{6}H{11}O){3} | Cocoa-nut and | | palm-nut oils
--------------------------------------------------------------------- Caprylin |
C{3}H{5}(O.C{8}H{15}O){3} | Do. do.
--------------------------------------------------------------------- Caprin |
C{3}H{5}(O.C{10}H{19}O){3} | Do. do.
--------------------------------------------------------------------- Laurin |
C{3}H{5}(O.C{12}H{23}O){3} | Do. do.
--------------------------------------------------------------------- Myristin |
C{3}H{5}(O.C{14}H{27}O){3} | Nutmeg butter
--------------------------------------------------------------------- Palmitin |
C{3}H{5}(O.C{16}H{31}O){3} | Palm oil, lard
--------------------------------------------------------------------- Stearin |
C{3}H{5}(O.C{18}H{35}O){3} | Tallow, lard, | | cacao butter
--------------------------------------------------------------------- Olein |
C{3}H{5}(O.C{18}H{33}O){3} | Olive and | | almond oils
--------------------------------------------------------------------- Ricinolein |
C{3}H{5}(O.C{18}H{33}O{2}){3} | Castor oil
---------------------------------------------------------------------
--------------------------------------------------------------------- Glyceride. |
Melting | Refractive | Saponification | Point, °C. | Index at 60° C. |

Equivalent. ---------------------------------------------------------------------
Butyrin | Liquid at -60 | 1.42015 | 100.7
--------------------------------------------------------------------- Isovalerin | ...
| ... | 114.7 ---------------------------------------------------------------------
Caproin | -25 | 1.42715 | 128.7
--------------------------------------------------------------------- Caprylin |
-8.3 | 1.43316 | 156.7
--------------------------------------------------------------------- Caprin | 31.1
| 1.43697 | 184.7
--------------------------------------------------------------------- Laurin | 45 |
1.44039 | 212.7
--------------------------------------------------------------------- Myristin |
56.5 | 1.44285 | 240.7
--------------------------------------------------------------------- Palmitin |
63-64 | ... | 268.7
--------------------------------------------------------------------- Stearin | 71.6
| ... | 296.7 ---------------------------------------------------------------------
Olein | Solidifies at -6 | ... | 294.7
--------------------------------------------------------------------- Ricinolein | ...
| ... | 310.7 ---------------------------------------------------------------------
Of the above the most important from a soap-maker's point of view are
stearin, palmitin, olein and laurin, as these predominate in the fats and
oils generally used in that industry. The presence of stearin and
palmitin, which are solid at the ordinary temperature, gives firmness to
a fat; the greater the percentage present, the harder the fat and the
higher will be the melting point, hence tallows and palm oils are solid,
firm fats. Where olein, which is liquid, is the chief constituent, we have
softer fats, such as lard, and liquid oils, as almond, olive and
cotton-seed.
Stearin (Tristearin) can be prepared from tallow by crystallisation from
a solution in ether, forming small crystals which have a bright pearly
lustre. The melting point of stearin appears to undergo changes and
suggests the existence of distinct modifications. When heated to 55° C.
stearin liquefies; with increase of temperature it becomes solid, and
again becomes liquid at 71.6° C. If this liquid be further heated to 76°

C., and allowed to cool, it will not solidify until 55° C. is reached, but if
the liquid at 71.6° C. be allowed to cool, solidification will occur at 70°
C.
Palmitin (Tripalmitin) may be obtained by heating together palmitic
acid and glycerol, repeatedly boiling the resulting product with strong
alcohol, and allowing it to crystallise. Palmitin exists in scales, which
have a peculiar pearly appearance, and are greasy to the touch. After
melting and solidifying, palmitin shows no crystalline fracture; when
heated to 46° C. it melts to a liquid which becomes solid on further
heating, again liquefying when 61.7° C. is reached, and becoming
cloudy, with separation of crystalline particles. At 63° C. it is quite
clear, and this temperature is taken as the true melting point. It has been
suggested that the different changes at the temperatures mentioned are
due to varying manipulation, such as rate at which the temperature is
raised, and the initial temperature of the mass when previously cool.
Olein (Triolein) is an odourless, colourless, tasteless oil, which rapidly
absorbs oxygen and becomes rancid. It has been prepared synthetically
by heating glycerol and oleic acid together, and may be obtained by
submitting olive oil to a low temperature for several days, when the
liquid portion may be further deprived of any traces of stearin and
palmitin by dissolving in alcohol. Olein may be distilled in vacuo
without decomposition taking place.
Laurin (Trilaurin) may be prepared synthetically from glycerol and
lauric acid. It crystallises in needles, melting at 45°-46° C., which are
readily soluble in ether, but only slightly so in cold absolute alcohol.
Scheij gives its specific gravity, d60°/4° = 0.8944. Laurin is the chief
constituent of palm-kernel oil, and also one of the principal
components of cocoa-nut oil.
Fatty Acids.--When a fat or oil is saponified with soda or potash, the
resulting soap dissolved in hot water, and sufficient dilute sulphuric
acid added to decompose the soap, an oily layer gradually rises to the
surface of the liquid, which, after clarifying by warming and washing
free from mineral acid, is soluble in alcohol and reddens blue litmus
paper. This oily layer consists of