When the wine has been drawn from the last vat, the marc in No. 1 having been washed six times with its weight of water, is exhausted of all its alcohol. It is then refilled with marc, and becomes No. 6 of the series, and is filled with the liquid from No. 5. Each number is thereby carried around the circle, becoming successively No. 6.
In this way the pomace is, little by little, deprived of its alcohol, and the liquid coming from No. 6 is rich in spirit, and when delivered to the still is nearly equal in strength to the original wine.
When there is but little marc to operate upon, the liquid may be drawn off into buckets, and so filled into the vats; but time and labor may be saved by using a pump and hose.
CHAPTER XIX.
THE COMPOSITION OF WINE.
Generally.—Wine is not only composed of alcohol and water, which are the two most prominent ingredients, but a great number of other substances have been recognized, and others still are supposed to exist. Some substances which are found in one wine may not exist in another, or it may exist in a greater or less quantity. We know that alcohol, water, and acids exist in all wines, in varying quantities; that some are sweet, and contain sugar, and that others are dry, thoroughly fermented, and contain none. We also know that the alcohol in different wines may vary from 4 or 5 per cent. in piquette made by washing the pomace with water, to 20 or 25 per cent. in the more strongly fortified. And we know generally how a wine is modified as to its taste and effect on the system, by such substances as water, alcohol, sugar, and acid; but there are many substances whose effect is but little known, and others again only known by their effects. The science of chemistry has not yet been able to lay hold of them.
Substances Recognized.—The following table from Maumené indicates the different substances contained in different wines, the letter F indicating those produced by fermentation, the others existing in the juice of the grape. It will be observed that the amount of acid tartrate of potash (cream of tartar) mentioned is 5.5 grammes per litre at most, and this is the quantity contained in a new wine, old wines containing only one or two grammes per litre, and even less. This salt is contained in the grapes, and is soluble in water, but insoluble in alcohol, and, therefore, the greater part of it is precipitated as the alcohol increases by fermentation, and is deposited with the lees. The Report of the University of California, Department of Agriculture, referred to in the preface, shows the amount contained in different California wines and their lees.
| Grammes. | ||||||
| Neutral Bodies. | Water | 9 volumes, | 900 to 891 | |||
| Common Alcohol (Absolute or Pure), | F. 1 volume, | 80 to 79 | ||||
| Other Alcohols (Butyric, Amylic, etc.) | F. | |||||
| Aldehydes (several?) | F. | |||||
| Ethers (Acetic, Butyric, œnanthic, etc.), | ||||||
| contributing principally to the bouquet | F. | |||||
| Essential Oils (several) | ||||||
| Grape Sugar (Dextrose and Levulose) | ||||||
| Mannite | F. | |||||
| Mucilage, Gum, and Dextrin | ||||||
| Pectin | ||||||
| Coloring Matters (œnocyanine) | ||||||
| Fatty Matters (and Wax?) | ||||||
| Glycerin | F. | |||||
| Nitrogenous Matters (Albumin, Gliadin, etc.) Ferments | ||||||
| Vegetable. | Acid Tartrate of Potash (5.5 grammes at most) | |||||
| Neutral Tartrate of Lime | ||||||
| ““Ammonia | ||||||
| Salts. | Acid Tartrate of Alumina (simple, or with Potash.) | |||||
| Acid Tartrate of Iron (simple, or with Potash.) | ||||||
| Racemates | ||||||
| Acetates, Propionates, Butyrates, Lactates, etc. | F. | — 20-30 | ||||
| Mineral. | Sulphates | |||||
| Nitrates | ||||||
| Phosphates | With a base of Potash, | |||||
| Silicates | Soda, Lime, Magnesia, | |||||
| Chlorides | Alumina, Oxide of Iron, | |||||
| Bromides | Ammonia | |||||
| Iodides | ||||||
| Fluorides | ||||||
| Free Acids.— | Carbonic (2.5 grammes at most) | F. | ||||
| Tartaric and Racemic (Gluco-tartaric?) | ||||||
| Malic | ||||||
| Citric | ||||||
| Tannic | ||||||
| Metapectic | F. | |||||
| Acetic | F. | |||||
| Lactic | F. | |||||
| Succinic | F. | |||||
| Butyric | F. | |||||
| Valeric? | F. | 1000-1000 | ||||
A few of the more important ones will be briefly noticed.
Alcohol is considerably lighter than water, and from the specific gravity of any mixture of alcohol and pure water, the quantity of spirit contained in it can readily be ascertained. (See [Table IV].)
Fig. 43.