After quickly cooling, the acid is neutralized with sodium hydrate of thirty-six times normal strength. Ten cubic centimeters of the hydrate solution will thus neutralize the sixty of hydrochloric acid which have been used to destroy the levulose. The work of Wiechmann discloses the fact, easily prevised, that the method used for destroying levulose is not always effective and that action of the reagent is not exclusively confined to the levogyrate constituent of the mixture. Nevertheless, data of reasonable accuracy may be secured by this process, which is best carried out as described by Wiechmann. In this connection the possibility of the polymerization of the dextrose molecules, when heated with hydrochloric acid, must not be overlooked.

248. The Analytical Process.—The total quantity of invert sugar in a given solution is determined by the methods already given ([136], [141].)

After this has been accomplished, the levulose is destroyed as described above, and the dextrose determined by any approved method ([136], [140]). In the presence of sucrose, the sum of the reducing sugars is first determined as in [136], [142]. After the inversion of the sucrose, the invert sugar is again determined, and the increased quantity found, calculated to sucrose. The levulose is then destroyed by hydrochloric acid, and the dextrose determined as described above. The quantity of sucrose may also be determined by an optical method ([91], [92], [94].).

249. Calculation of Results.—If we represent by a the weight of metallic copper reduced by the invert sugar present in a solution containing sucrose, and by b that obtained after the inversion of the sucrose, the quantity of copper corresponding to the sucrose is b - a = c. After the destruction of the levulose, the copper reduced by the residual dextrose may be represented by d. The weight of copper equivalent to the levulose is, therefore, b - d = e. From the tables already given, the corresponding quantities of the sugars equivalent to c, d, and e are directly taken. Example:

a =300milligrams = 163.8milligramsinvert sugar.
156.5”dextrose.
185.63”levulose.
b =500”
d =275”= 142.8”dextrose.
c =200”= 106.3”invert sugar.
e =225”= 133.89”levulose.

The 106.3 milligrams of invert sugar equivalent to c, correspond to 101 milligrams of sucrose. The quantity of dextrose equivalent to 275 milligrams of copper is 142.8. Of this amount 53.15 milligrams are due to the inverted sucrose, leaving 89.65 milligrams arising from the invert sugar and dextrose originally present. This quantity is equivalent to 175 milligrams of copper.

Of the 300 milligrams of copper obtained in the first instance, 125 are due to levulose in the original sample, corresponding to 69.73 milligrams which number, multiplied by two, gives the invert sugar present.

The sample examined, therefore, had the following composition:

Sucrose101.00milligrams.
Invert sugar  139.46”
Dextrose19.92”
Sum260.38”