ss of alkali is
titrated with N/1 hydrochloric or sulphuric acid.

The value of the approximately N/2 alkali solution is ascertained by
taking 50 c.c. together with 30 c.c. neutral alcohol in a similar flask,
boiling for the same length of time as the fat, and titrating with N/1
hydrochloric or sulphuric acid. The "saponification equivalent" is the
amount of fat or oil in grammes saponified by 1 equivalent or 56.1
grammes of caustic potash.

_Example._--1.8976 grammes fat required 18.95 c.c. N/1 acid to
neutralise the unabsorbed alkali.

Fifty c.c. approximately N/2 alcoholic potash solution required 25.6
c.c. N/ acid..

25.6 - 18.95 = 6.65 c.c. N/1 KOH required by fat.

1.8976 x 1000 / 6.65 = 285.3 Saponification Equivalent.

The result of this test is often expressed as the "Saponification
Value," which is the number of milligrammes of KOH required for the
saponification of 1 gramme of fat. This may be found by dividing 56,100
by the saponification equivalent or by multiplying the number of c.c. of
N/1 alkali absorbed, by 56.1 and dividing by the quantity of fat taken.
Thus, in the above example:--

6.65 x 56.1 / 1.8976 = 196.6 Saponification Value.

The _ester_ or _ether value_, or number of milligrammes of KOH required
for the saponification of the neutral esters or glycerides in 1 gramme
of fat, is represented by the difference between the saponification and
acid values. In the example given, the ester value would be 196.6 - 15.3
= 181.3.

_Unsaponifiable Matter._--The usual method adopted is to saponify about
5 grammes of the fat or oil with 50 c.c. of approximately N/2 alcoholic
potash solution by boiling under a reflux condenser with frequent
agitation for about 1 hour. The solution is then evaporated to dryness
in a porcelain basin over a steam or water-bath, and the resultant soap
dissolved in about 200 c.c. hot water. When sufficiently cool, the soap
solution is transferred to a separating funnel, 50 c.c. of ether added,
the whole well shaken, and allowed to rest. The ethereal layer is
removed to another separator, more ether being added to the aqueous soap
solution, and again separated. The two ethereal extracts are then washed
with water to deprive them of any soap, separated, transferred to a
flask, and the ether distilled off upon a water-bath. The residue, dried
in the oven at 100 deg. C. until constant, is the "unsaponifiable matter,"
which is calculated to per c