Though there are many tests in use for the discovery of the presence of mineral poisons, such as litharge and other preparations of lead, or pungent vegetable nostrums, namely extract of capsicums, &c. in wines and spirits, yet it must be admitted that there are no efficient tests for detecting the presence of the foreign agents above mentioned in either wines or spirits, except by chemical analysis; because, in the fraudulent combination which takes place, those articles bear the largest proportions which possess the same chemical properties as do the wines and spirits with which they are compounded. The injurious tendency of the vegetable poisons which form a component part of the spurious compositions which are vended under the denomination of cheap wines and spirits, and their injurious and lingering effects are so imperceptible on the human constitution, that, as the author of “The Oracle of Health and Long Life” observes, they must be deadly indeed to produce immediate injury, so as to give suspicion of their presence.
The presence of sugar of lead, or any other deleterious metal in wine, may be detected by filling a glass with wine, and adding a few drops of Harrowgate-water, or melted brimstone, when the wine will with the last mentioned ingredient becomes blackish, and with the other it will immediately produce a black sediment; but if it be unadulterated it will only lose its clearness, taste, and colour. Or the adulteration may be discovered by adding one part of water saturated with sulphuretted hydrogen gas, acidulated with a small portion of muriatic acid, to two parts of wine, or any other liquid, in which the presence of lead is suspected, when a blackish coloured precipitate will settle at the bottom of the vessel, which, being dried and fused by means of the blow-pipe, will yield a globule of metallic lead. The prussiate of potash is occasionally employed for the same purpose: a drop or two being sufficient to show a white or greyish precipitate in any fluid in which lead is contained. When white wines have an unusual degree of sweetness, are of a darker colour than their age and body seem to warrant, and particularly when their use, or that of the red wines, is followed by pains in the stomach, it may be concluded that they have been adulterated with lead.
The process to detect the presence of alum in wine, is to take some fresh prepared lime-water, and to mix the suspected wine with it, in about equal proportions; if after the mixture has stood about a day, a number of crystals is found deposited at the bottom of the vessel, the wine is genuine; but, if alum is present in the wine, there will be no crystals, but a slimy and muddy precipitate. Or the presence of alum may be detected, by dropping some solution of subcarbonate of potash into the wine, when, if the alum be present, there will be a violet coloured precipitate, or at least cloudiness, which will vanish again if a few drops of caustic, potash, or of muriatic acid are added to the mixture.
Where artificial colouring matter is suspected in wine, put a quarter of a pint of the liquor into a phial, with an ounce of fresh charcoal finely pulverized. Then shake the mixture well for a few minutes, when, if the wine is impregnated only with its own natural colouring, that colour will be chemically destroyed, and the wine, when filtered, will yield a clear limpid fluid; but, if the wine is artificially coloured, such artificial colours will not be acted on by the charcoal, and the mixture will appear unchanged.
Extraneous colours in wines may also be detected by means of acetate of lead. If this test produces, in red wine, a greenish grey precipitate, it is a sign that the wine is genuine. Wine coloured with the juice of bilberries, or elderberries, or Campeachy wood, produces, with acetate of lead, a deep blue precipitate; and fernambouk wood, red saunders, and the red beet, produce a red precipitate by the agency of the acetate of lead.
According to Cadet (Dictionnaire de Chimie, art. Vin.) this species of adulteration may be detected by pouring into the suspected wine a solution of sulphate of alumine, and precipitating the alum by potash. If the wine is pure, the precipitate will have a bottle green colour, more or less dark, according to the natural hue of the wine. But if the colour has been artificial the following will be the results:—
| Tournesol | will give a precipitate of | a bright yellow colour. |
| Brazil wood | a brownish red colour. | |
| Elderberries or privet | a brownish violet colour. | |
| Wortleberries | the colour of dirty wine lees. | |
| Logwood | a lake red colour. |
But Dr. Henderson says, in his learned work, entitled “The History of Ancient and Modern Wines,” p. 342, that the simple test pointed out to him by his friend Dr. Prout is equally satisfactory, and may be applied either to red or white wines. “On adding ammonia to wines, which had the appearance of being genuine, he observed that the precipitate was of an olive green colour; shewing the analogy between the colouring principle and the vegetable blues, most of which are rendered red by acids, and green by alkalis. This conjecture is, in some measure, confirmed by the recent discovery of M. Breton, professor of chemistry in Paris, with respect to the cause of that disorder in wines known by the name of tournure. Wine thus affected acquires a disagreeable taste and smell, loses its red colour, and assumes a dark violet hue, which changes are found to proceed from the presence of carbonate of potash, in consequence of the decomposition of the tartar contained in the liquor. To restore the natural colour and flavour, if the disease be not of long standing, it is only necessary to add a small quantity of tartaric acid, which, combining with the potash, forms cream of tartar, as is shown by the subsequent deposition of crystals. Revue Encyclopedique, November, 1823. In genuine wines, the colouring matter seems to partake of the character of a lake, partly held in solution by the excess of acid present, and partly combined with the earthy phosphates; for, in the precipitates obtained from these wines by means of ammonia, it appears in union with the triple phosphate of magnesia. Even the white wines of Xeres, Madeira, and Teneriffe, exhibit this mixed precipitate; their colouring matter being probably derived from the red grapes which enter into their composition. In fictitious wines, on the other hand, such as those procured from the black currant, gooseberry, orange, &c. the last mentioned salt was thrown down by ammonia, but more gradually, in less quantities, and without any admixture.”
The method of ascertaining the strength, or quantity of spirit or alcohol in wines is by the following process, for the discovery of which the public is indebted to Mr. Brande.
“Add to eight parts, by measure, of the wine to be examined, one part of a concentrated solution of subacetate of lead; a dense insoluble precipitate will ensue; which is a combination of the test-liquor with the colouring, extractive and acid matter of the wine. Shake the mixture for a few minutes, pour the whole upon a filter and collect the filtered fluid. It contains the brandy, or spirit, and water of the wine, together with a portion of the subacetate of lead. Add, in small quantities at a time to this fluid, warm, dry, and pure subcarbonate of potash, (not salt of tartar, or the subcarbonate of potash of commerce); which has previously been freed from water by heat, till the last portion added remains undissolved. The brandy or spirit contained in the fluid will become separated; for the subcarbonate of potash abstracts from it the whole of the water, with which it was combined; the brandy or spirit of wine forms a distinct stratum, which floats upon the aqueous solution of the alkaline salt. If the experiment be made in a glass tube, from one half inch to two inches in diameter, and graduated into a hundred equal parts, the per centage of spirit, in a given quantity of wine, may be read off by mere inspection. In the same manner the strength of any wine may be examined.”