The Wine Press and the Cellar: A Manual for the Wine-Maker and the Cellar-Man

by Emmet H. Rixford

French Still.

To Ascertain the Alcoholic Strength of Wine, if it consisted of a mixture of water and alcohol alone, it would only be necessary to learn its specific gravity; but as all wines contain other substances which affect the weight of the liquid, it becomes necessary to separate the alcohol from the other matters by distillation; then by adding water enough to make up the original volume of the wine assayed, we will have simply a mixture of alcohol and water.

Small stills are sold in the market, with the necessary instruments accompanying them, with which to perform the operation. In the accompanying figure [(43)], which shows a French still, L is a spirit lamp, B a glass boiler with a perforated stopper, S a worm, contained in the cooler D, which is kept filled with cold water, as a condenser; t is a rubber tube connecting the boiler with the condenser, tightly fitted to the stopper of the former, and also to the end of the worm. E is a small hydrometer-jar, of glass, with a foot, for measuring the wine to be distilled, and for catching the distillate as it runs from the worm. It has three marks—the upper one, m, indicating the height to which it is to be filled with the wine, and also a ½ mark and a ⅓ mark. Sometimes it is provided with a groove along one side to carry the thermometer. A represents the hydrometer, or alcoholometer, being a spindle, usually of glass, similar in form to the saccharometer (which see), except that the zero mark to which the alcoholometer sinks in distilled water, is at the lower end of the stem, and the degrees are numbered from zero to the upper end, each figure representing one per cent. of alcohol. T is a thermometer, in its place in the jar with the hydrometer; t′ is a small glass pipette to assist in filling the jar just to the mark.

To make use of the instruments, measure in the jar, E, the wine to be distilled, by filling it up exactly to the upper mark, m, using the pipette, t′, by which a little of the liquid can be sucked up, and let out, drop by drop, by increasing and diminishing the pressure of the finger applied to the upper opening. The wine so measured is poured into the boiler, B, draining out the last drop, or the little remaining may be rinsed out with a little water, which is poured into the boiler with the wine without affecting the result. The boiler is then placed over the lamp and connected with the condenser by means of the rubber tube, and the condenser filled with cold water. Light the lamp, and place the now empty jar under the lower end of the worm. The vapor of the alcohol first passing from the boiler through the rubber tube into the condenser, will there condense, and the liquid running from the worm into the test tube will be almost pure alcohol, but as the process goes on, more and more water comes out with the alcohol, till the spirit has all passed over. If the strength of the wine does not exceed 14 or 15 per cent., the alcohol will all have passed over when one-third of the wine has been distilled, as will be shown when the distillate reaches the ⅓ mark on the glass. If the strength exceeds the above limit, one-half of the wine should be distilled. If, therefore, on testing the wine, it is found to contain 16 per cent. or more of spirit, and only one-third was distilled, another quantity should be distilled, and about one-half allowed to pass over. It is always safer, unless the wine is very weak, to distil over a little more than a third. If you are operating on a wine which foams to such an extent that a portion may pass through the tube into the condenser, which would spoil the effect of the operation, this may be prevented by putting into the boiler with the wine a pinch of tannic acid. In operating on a wine which contains an appreciable amount of acetic acid—is pricked—the acid ought to be neutralized before distillation, as it is volatile, and will go over with the alcohol and effect the result. This is easily done by adding to the wine caustic soda in drops, till it completely changes color, red wine becoming blue, and white wine, brown. These precautions, however, are generally omitted in analyses for commercial purposes.

When the distillation is complete, add to the distillate sufficient pure water (distilled water if possible), to make up the exact volume of wine measured. To do this, take the jar containing the distillate and hold it perpendicular, with the upper mark on a level with the eye, and carefully let in the water, drop by drop, by means of the pipette. The surface of the liquid will be seen to curve upward, owing to the attraction of the glass, and the tube should be filled till the bottom of the curve touches the mark; and the same precaution should be taken in measuring the wine in the first place.

Now we have a mixture corresponding in volume with the wine, and containing all the alcohol originally contained in the wine, and a certain amount of water, and nothing else.

As the density of the liquid also depends upon the temperature, it becomes necessary to have a fixed standard at which the test is made, and this is 60° F. in this country, and I believe in all countries except France, where it is 15° C., or 59° F. As the temperature affects the volume, it is better to adjust it by cooling the distillate before adding the last few drops of water, which may be done by dipping the jar into cold water, or if it is too cold, by warming it with the hand.

The hydrometer used will be adjusted to a temperature of 60° F., or 15° C., which is generally shown by directions accompanying the still, or will be marked on the instrument. Let the hydrometer be perfectly clean and dry, no moisture on the stem. Take the tip of the stem between the thumb and forefinger and lower it into the distillate till it floats, press it down with the finger very slightly, and let it come to equilibrium. Place the eye on a level with the surface of the liquid, and see where it cuts the stem, and the mark shows the percentage of alcohol contained in the wine. Remember that the mark to be taken is the one corresponding with the general surface of the liquid, not the top of the meniscus, or curve. With care, a result can be obtained sufficiently accurate for all commercial purposes.

Fig. 44.