Part 118

(a) The sugar is inverted:

(a₁) It rotates to the left after inversion.—Unfermented cane sugar is present.

(a₂) It rotates more than 2°.3 to the right.—The unfermentable constituents of commercial dextrose are present.

(a₃) It rotates less than 2°.3 and more than 0°.9 to the right.—It is in this case treated as follows:

Two hundred and ten cubic centimeters of the sample are evaporated to a thin sirup with a few drops of a twenty per cent solution of potassium acetate. To the residue 200 cubic centimeters of ninety per cent alcohol are added with constant stirring. The alcoholic solution is filtered into a flask and the alcohol removed by distillation until about five cubic centimeters remain. The residue is mixed with washed bone-black, filtered into a graduated cylinder and washed until the filtrate amounts to thirty cubic centimeters. When the filtrate shows a dextrorotation of more than 1°.5, it indicates the presence of unfermentable constituents of commercial dextrose.

(3) There is left rotation.—The sample contains unfermented levorotatory sugar, derived either from the must or mash or from the inversion of added cane sugar. It may, however, also contain unfermented cane sugar and the unfermentable constituents of commercial dextrose.

(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.

Pure wines give filtrates which are colorless or light yellow, while the presence of a more or less red coloration indicates that an anilin color has been added to the wine.

(b) Method of Sostegni and Carpentieri.—Evaporate the alcohol from 200 cubic centimeters of wine. Add from two to four cubic centimeters of a ten per cent solution of hyrochloric acid, immerse therein some threads of fat-free wool and boil for five minutes. Remove the threads, wash them with cold water acidified with hydrochloric, then with hot water acidified with hydrochloric, then with pure water and dissolve the color in a boiling mixture of fifty cubic centimeters of water and two cubic centimeters of concentrated ammonia. Replace the threads by new ones, acidify with hydrochloric and boil again for five minutes. In the presence of anilin colors to the amount of two milligrams per liter, the threads are dyed as follows:

Safranin light rose-red. Vinolin rose-red to violet. Bordeaux-red rose-red to violet. Ponceau-red rose-red. Tropæolin oo straw yellow. Tropæolin ooo light orange.

(c) Detection of Fuchsin and Orseille.—To twenty cubic centimeters of wine add ten cubic centimeters of lead acetate solution, heat slightly and mix by shaking. Filter into a test-tube, add two cubic centimeters of amyl alcohol and shake. If the amyl alcohol be colored red, separate it and divide it into two portions. To one add hydrochloric acid, to the other ammonia. When the color is due to fuchsin, the amyl alcohol will in both cases be decolorized; when due to orseille, the ammonia will change the color of the amyl alcohol to purple-violet.

=640. Determination of Ash.=—The residue from the direct extract determination is incinerated at as low a heat as possible. Repeated moistening, drying and heating to low redness is advisable to get rid of all organic substances. When a quantitive analysis of the ash is desired, large quantities of the sample are evaporated to dryness and the residue incinerated with the usual precautions.

=641. Determination Of Potash.=—(a) Kayser’s Method.—Dissolve seven-tenths gram pure sodium hydroxid and two grams of tartaric acid in 100 cubic centimeters of wine, add 150 cubic centimeters of ninety-two to ninety-four per cent alcohol and allow the liquid to stand twenty-four hours. The precipitated potassium bitartrate is collected on a small filter and washed with fifty per cent alcohol until the filtrate amounts to 260 cubic centimeters. The precipitate and filter are transferred to the beaker in which the precipitation was made, the precipitate dissolved in hot water, the volume made up to 200 cubic centimeters and fifty cubic centimeters thereof titrated with decinormal sodium hydroxid solution, adding 0.004 gram to the final result, representing the potash which remains in solution as bitartrate.

(b) Platinum Chlorid Method.—Evaporate 100 cubic centimeters of the wine to dryness, incinerate the residue and determine the potash as in ash analysis.

=642. Determination of Sulfurous Acid.=—One hundred cubic centimeters of wine are distilled in a current of carbon dioxid, after the addition of phosphoric acid, until about fifty cubic centimeters have passed over. The distillate is collected in accurately set iodin solution. When the distillation is finished, the excess of iodin is determined with set sodium thiosulfate solution and the sulfurous acid calculated from the iodin used.

=643. Detection of Salicylic Acid.=—(a) Spica’s Method.—Acidify 100 cubic centimeters of the liquor with sulfuric and extract with sulfuric ether. Evaporate the extract to dryness, warm the residue carefully with one drop of concentrated nitric acid and add two or three drops of ammonia. The presence of salicylic acid in the liquor is indicated by the formation of a yellow color due to ammonium picrate and may be confirmed by dyeing therein a thread of fat-free wool.

(b) Bigelow’s Method.—Place 100 cubic centimeters of the wine in a separatory funnel, add five cubic centimeters of sulfuric acid (1-3) and extract with a sufficient quantity of a mixture of eight or nine parts of ether to one part of petroleum ether. Throw away the aqueous part of the extract, wash the ether once with water, then shake thoroughly with about fifty cubic centimeters of water, to which from six to eight drops of a one-half per cent solution of ferric chlorid have been added. Discard the aqueous solution, which contains the greater part of the tannin in combination with iron, wash again with water, transfer the ethereal solution to a porcelain dish and allow to evaporate spontaneously. Heat the dish on the steam bath, take up the residue with one or two cubic centimeters of water, filter into a test-tube and add one to two drops of one-half per cent solution of ferric chlorid. The presence of salicylic acid is indicated by the appearance of a violet-red coloration. In the case of red wines, a second extraction of the residue with ether mixture is sometimes necessary. This method cannot be used in the examination of beers and ales.

(c) Girard’s Method.—Extract a portion of the acidified liquor with ether as in the preceding methods, evaporate the extract to dryness and exhaust the residue with petroleum ether. The residue from the petroleum ether extract is dissolved in water and treated with a few drops of a very dilute solution of ferric chlorid. The presence of salicylic acid is indicated by the appearance of a violet-red coloration.

=644. Detection of Gum and Dextrin.=—Four cubic centimeters of the sample are mixed with ten cubic centimeters of ninety-six per cent alcohol. When gum arabic or dextrin is present, a lumpy, thick and stringy precipitate is produced, whereas pure wine becomes at first opalescent and then gives a flocculent precipitate.