SAPONIFIABLE -OILS, FATS AND WAXES

187

water and add 25 cc of dilute sulphuric acid (50 cc in 1000 cc of solution)
and a small amount of crushed porcelain or pumice. Connect with a
condenser by means of a distilling'tube (Fig. 46) and distill into a flask
which is graduated at 100 cc and 110 cc; the distillation should proceed
at such a rate that 110 cc passes over in about 20 minutes. When the
distillate reaches the 110-cc mark on the flask replace the latter by a 25-cc
cylinder and stop the distillation. Immerse the flask in water at 15° and
allow to remain for 15 minutes. The level of the water must be above the
110-cc mark on the flask. Mix the contents of the flask and pass through
a dry, 8-cm filter and, if desired, determine the Reichert-Meissl number,
using 100 cc of the filtrate. Rinse the 110-cc flask but without removing
any of the insoluble acids adhering to it. Wash the filter three times with
15 cc of water, this water having previously been used for washing the con-
denser, cylinder and flask. Dissolve the insoluble acids from the con-
denser, cylinder and filter, using three successive portions of neutral (to
phenolphthalein) 90-per cent alcohol and allowing the solution to run into
the 110-cc flask. Titrate the alcoholic solution with tenth-normal potassium
hydroxide solution, using phenolphthalein, and calculate the Polenske value.

Acetyl Value.—Compounds containing a hydroxyl group will
readily combine with acetic anhydride, acetic acid and an acetyl
compound being produced. This takes place with an oil con-
taining free higher alcohols or hydroxy-acids, the latter either in
the form of esters or of free acids. For example lanopalmic acid
forms acetolanopalmic acid:

(CH3CO)20 -» Ci6H30OCH3COCOOH +

CHsCOOH. (1)

After washing out the excess of acetic anhydride the amount
absorbed may be determined by saponifying the oil with an
alcohol solution of potassium hydroxide, evaporating the alcohol,
adding standard sulphuric or hydrochloric acid to liberate the
acetic and fatty acids and either distilling the acetic acid or
washing out with waiter, then titrating. The reactions illustrated
by the case of aceto-lanopalmitin are

+ 6KOH -» C3H6(OH)3 +
3C15H30OHCOOK + SCHsCOOK. (2)
2C15H30OHCOOK + H2SO4 -» 2C15H30OHCOOH + K8SO4, (3)
2CH3COOK + H2SO4 -> CH3COOH + K2SO4. (4)