(a) The wine sugars are fermented according to directions in [262].
(a₁) It polarizes 3° after fermentation.—It contains only levorotatory sugar.
(a₂) It rotates to the right.— It contains both levorotatory sugar and the unfermentable constituents of commercial dextrose.
(b₁) The sucrose is inverted according to (c), in (2).
(b₂) It is more strongly levorotatory after inversion. In contains both levorotatory sugar and unfermented cane sugar.
637. Estimation of Sucrose, Dextrose, Invert Sugar, Maltose and Dextrin.—The total and relative quantities of these carbohydrates are determined by the processes already described ([237-262]).
638. Determination of Glycerol.—(a) In Dry Wines and Beers.—One hundred cubic centimeters of wine are evaporated in a porcelain dish to about ten cubic centimeters, a little quartz sand and milk of lime added and the evaporation carried almost to dryness. The residue is mixed with fifty cubic centimeters of ninety per cent alcohol, using a glass pestle or spatula to break up any solid particles, heated to boiling on the water bath, allowed to settle and the liquid filtered into a small flask. The residue is repeatedly extracted in a similar manner, with small portions of boiling alcohol, until the filtrate in the flask amounts to about 150 cubic centimeters. A little quartz sand is added, the flask connected with a condenser and the alcohol slowly distilled until about ten cubic centimeters remain. The evaporation is continued on the water bath until the residue becomes sirupy. It is cooled and dissolved in ten cubic centimeters of absolute alcohol. The solution may be facilitated by gentle heating on the steam bath. Fifteen cubic centimeters of anhydrous ether are added, the flask stoppered and allowed to stand until the precipitate has collected on the sides and bottom of the flask. The clear liquid is decanted into a tared weighing bottle, the precipitate repeatedly washed with a few cubic centimeters of a mixture of one part of absolute alcohol and one and five-tenths parts anhydrous ether and the washings added to the solution. The ether-alcohol is evaporated on the steam bath, the residue dried one hour in a water oven, weighed, the amount of ash determined and its weight deducted from that of the weighed residue to get the quantity of glycerol.
(b) In Sweet Wines.—One hundred cubic centimeters of wine are evaporated on the steam bath to a sirupy consistence, a little quartz sand being added to render subsequent extraction easier. The residue is repeatedly treated with absolute alcohol until the united extracts amount to from 100 to 150 cubic centimeters. The solution is collected in a flask and for every part of alcohol one and five-tenths parts of ether are added, the liquid well shaken and allowed to stand until it becomes clear. The supernatant liquor is decanted into a beaker and the precipitate washed with a few cubic centimeters of a mixture of one part alcohol and one and five-tenths parts ether. The united liquids are distilled, the evaporation being finished on the water bath, the residue is dissolved in water, transferred to a porcelain dish and treated as under (a).
639. Determination of Coloring Matters in Wines.—The methods of detecting the more commonly occurring coloring matters in wines as practiced by the official chemists are given below.
(a) Cazeneuve Reaction.—Add two-tenths gram of precipitated mercuric oxid to ten cubic centimeters of wine, shake for one minute and filter.