Methods For Detecting The Presence Of Artificial Colouring Matter In Wines.

Practical Magazine 23, 1876

For some years past the wine trade has been in a state of alarm, in consequence of the large quantities of wine which have been ascertained to be coloured artificially by means of chemical substances, such as fuchsine, which is extracted from coal-tar and is used for dyeing red and rose pink. At Nancy, in several towns of Alsace-Lorraine, in the south of France, and quite recently at Paris, wine has been seized — provisionally sequestered — on suspicion of adulteration. An official analysis having taken place, these wines were found to be adulterated with fuchsine, which was intended either to impart a richer tint to the beverage, or to give the vinous robe to mixtures which only contained a few elements of the juice of the grape. It is a positive fact that in Alsace-Lorraine they manufacture, ostensibly and wholesale, beverages which only have the name of wine. Pungent decoctions (riguettes) which, like "husband's tea," are obtained from the residue of the wine-press, are made to ferment once more by the addition of water diluted with glucose, thus producing an alcoholic liquid, which is artificially coloured by caramel or with althaea (the arborescent hollyhock or rose mallow), cochineal, orchil, elder-berries, phytolaque, fuchsine, &c., and these wines are then labelled and sent into the market as growths of different localities and ages. The lighter wines of the south of France, sometimes called "lowland" wines (vins de la plaine), often are merely wines of a second pressing, with an addition of colouring matter and tartaric acid. The wines exported to France from Italy and Spain are all artificially coloured with elderberries and tartaric acid. Things have gone so far that the syndicate of the wine-growers at Narbonne have petitioned the Minister of Agriculture to prohibit the importation of Spanish wines. In a letter from M. Paul Massot, deputy of the Pyrénées-Orientales, to the Minister of Justice, this gentleman points out the facts which are so important to the public, and stigmatizes the perpetrators of these criminal frauds. "The Spanish, Portuguese, and Italian wines," says M. Massot, "which are tinted with bays, have for a long time competed in a way fatal to the French produce; but this fraud, having been adopted, imitated, and improved upon by a large number of unscrupulous French merchants, or which, perhaps, has already been employed by certain proprietors in districts where the vintage is the most abundant, has taken such an extension, that the finest wines of the Narbonne, Lot, Gironde, and especially the Roussillon districts, are now completely abandoned. The druggers, who formerly constituted an imperceptible minority in the wine-growing world, generally only used to employ harmless vegetable substances. They have become legion now, and are not afraid of using poisons. Fuchsine is consumed by the hundredweight. Grenator garnet, a secondary product of the manufacture of fuchsine, used to be unsaleable, but is now sold at a remunerative price; and the reason for it is obvious — there are very few products sold for colouring wines under such fancy names as colorine, caramel, &c., but contain aniline, salts of rosaniline, or residues of fuchsine."

M. Massot gives the particulars to show to what degree public health is jeopardized by this immense system of adulteration. The "Annales d'Hygiène Publique" state that in the village of Odeillan alone a Narbonne grocer has sold 10,000 fr. (£400) worth of ammoniacal cochineal. Small dealers are known to clear as much as 30,000 fr. (£1,200) profits from the sale of wine-colouring matter.

A great number of these preparations are injurious to public health, and if the others, almost all of them laxative, might be considered as inoffensive — a thing evidently impossible, since upwards of seven grammes (½ oz.) of alum has been found in a litre of wine-coloured by elder-berries — they all constitute a fraud which the magistrate is in duty bound to repress.

The Custom-house officers and excisemen, who used to judge wines by the look, and taste them with their tasse (a flat silver saucer, with a finger-handle), being unable to detect whether wines had been so drugged in the manner stated, chemistry had to be resorted to.

Chemists hitherto had great difficulty to discover with certainty the nature of the tinctorial matters used for that purpose. Under the pressure of circumstances and the gravity of the facts, some savants, however, have succeeded in devising special methods, which allow any person to detect the nature of the spurious compounds fraudulently added to wines for brightening their colour, or entirely changing it. M. V. Didelot, a druggist at Nancy, has quite recently published a book under the title, "Processes for Detecting the Adulteration of Wines," which contains several practical recipes easy to be understood and followed.

In order to find out the colouring matters M. Didelot puts into a liqueur glass a small ball of gun-cotton, with 10 or 15 grammes (1/3;-½ oz.) of wine. The glass is shaken for a few seconds, and the cotton then washed. If the wine is pure, or what may be termed "achrozotic," the cotton comes out white; otherwise it remains coloured by the fuchsine or other tinctorial matter. In case there should be any doubt, or the coloration of the cotton be not decisive enough, M. Didelot advises to put the gun-cotton into a small tube and heat the same with a spirit lamp, which will produce the reaction with all the preciseness desirable.

Gun-cotton indicates nearly every dyeing matter superadded to wine. With a few drops of ammonia it is even possible to determine the matter used. Thus, a few drops of it sprinkled on the gun-cotton decolour it if it has been dyed by fuchsinated wine. It takes a violet tint when the wine has been coloured by means of orchil, and a greenish hue when it has been adulterated with hollyhock leaves or the stalky mallow.

This process, however, would be defective if the wine had been drugged, not with one, but several substances. A separate process in that case is requisite for each of the matters looked for. Fuchsine being the most dangerous of tinctorials, owing to being often prepared from aniline and by means of arsenic acid, M. Didelot gives us a special method for the discovery of that chemical.

This method consists in pouring into a test-glass closed by a tap, or into a glass funnel closed by a stopper, 10 to 15 grammes (1/3;-½ oz.) of the sophisticated wine, adding to it several grammes of ammonia and about five grammes of sulphuric ether. The whole is then well shaken, and left at rest for a few minutes, after which the liquid is decanted by the tap so as to draw off the supernatant ether. This ether is poured on a small ball of gun-cotton, and then some drops of acetic acid or strong vinegar are spilt on it. When there is fuchsine in the wine the azotic cotton at once assumes a rosy tint. When no funnel or test-glass is at hand, the mixture of wine, ammonia, and ether is shaken in a common liqueur glass and let alone for some minutes. A small bit of gun-cotton is steeped in the supernatant ether, put on a plate or saucer, and some vinegar dropped on it. The presence of fuchsine is proved by the cotton thus treated showing a rose-pink colour.

An Italian chemist, M. Lamaltina, has communicated a process which differs from M. Didelot's. Fifteen grammes (½ oz.) of peroxide of manganese, coarsely pulverized, is mixed with 100 grammes (about 3½ oz.) of wine, the mixture to be shaken for a quarter of an hour. It is then filtered, and if the wine comes out colourless it is pure, but if it keeps its colour it certainly has been coloured artificially. This process is said to be excellent, provided the peroxide of manganese be pure. Care must be taken not to employ ferruginous manganese, for the acids and salts in the wine would dissolve the iron and thus interfere with the re-actions.

Another chemical agent (chloroform) may be used for detecting fuchsine and other fraudulent matter in the wine. Three or four grammes weight of wine, as much water, and about two grammes of chloroform, are poured into a tube, closed at one orifice. The tube is then thoroughly shaken, closing it at the other end with the thumb, and leaving it to settle for a few minutes. The chloroform precipitates at the bottom of the tube, bringing down a portion of the artificial colouring matter held in the wine. With pure wines, chloroform produces a light grey, slightly rosy, half transparent or diaphanous precipitate, which separates into two strata, the lower of which becomes limpid after a few hours' rest.

The addition of one centigramme of fuchsine to wine yields, with chloroform, a characteristic precipitate of a rosy violet shade, which grows richer as more fuchsine is added. After several hours' settling the precipitate separates, and the lower portion clarifies.

The precipitate produced by chloroform on orchil is of a bluish grey, turning into a red brown in the lapse of a few hours, darkening with time, and never separating.

With the same test, cochineal produces a dirty grey and rather violet precipitate; the rose trémieré, or hollyhock, a violet rose. The simultaneous presence of orchil and fuchsine turns the results of the latter into a brownish red precipitate. Caramel (burnt sugar) gives the characteristics of fuchsine and orchil combined — a dark violet-red precipitate. For want of chloroform benzine may be used. The reactions in this case are nearly the same, only the colouring matter supernatates, and forms a kind of jelly with the benzine. M. Paul Massot justly demands that the law against sophistication of wine should be made as strict, and enforced as severely, as is done now in reference to other articles of food; and he suggests, that at the opening of the Chambers a special bill be brought in to efficiently put down these scandalous practices, which are so injurious to public health, and sap the reputation and prosperity of the wine trade in France, and elsewhere, at its very foundation.

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