Cerebral substances.—Adulteration by these substances is probably of much less frequent occurrence than was formerly supposed. The admixture is detected by evaporating the milk to dryness, dissolving the residue in ether, evaporating the etherial solution, and fusing the second residue, which consists of fatty matters, with nitrate of potassa in a platinum crucible. The mass is then taken up with water, and chloride of barium added to the solution. If cerebral substances were contained in the milk, ether will dissolve the fatty matters present, the phosphorus of which is converted into a soluble phosphate by the calcination with nitrate of potassa and is thrown down as a white precipitate, upon the addition of a solution of chloride of barium. This test may be confirmed by a microscopic examination of the milk, when the peculiar appearance of cerebral matter will be detected.[U]
WINE.
The most common adulteration to which wines are subjected is the addition of water: wines having a rich color are frequently mixed by the dealer with lighter wines, and the fraud consummated by adding water. The detection of this adulteration is somewhat difficult, as water is a normal constituent of wine. In Paris the following method is usually employed: As soon as the wine is confiscated, it is ascertained what kinds of wine are manufactured by the inculpated dealer, and a statement obtained from him, giving the proportions of alcohol, etc., contained in the various brands. A wine is then prepared, according to the information received, an estimation of the alcohol contained in the prepared sample made, and the results compared with those furnished by a similar examination of the suspected wine. In case the proportion of alcohol is less in the suspected wine than in the prepared sample, it is evident that a fraudulent adulteration has been committed. If, however, the quantity of alcohol is the same in both wines, it does not necessarily follow that the wine has escaped admixture, since this body may have been added after the adulteration with water. In addition to the estimation of alcohol, it is also necessary to determine the amount of cream of tartar (bitartrate of potassa) present, as the proportion of this salt would be sensibly decreased by the addition of alcohol and water to the wine. This fraud could, however, be disguised by subsequently adding the proper amount of cream of tartar.
It is also well to ascertain if two equal quantities of the prepared sample and the wine under examination require the same amount of solution of hypochlorite of lime for decolorization. In case the suspected wine has been adulterated, the quantity of hypochlorite solution used will be less than the amount necessary to decolorize the prepared wine. Foreign coloring matter may be added by the adulterator, but this fraud is easily detected by adding potassa to the sample: if its coloration is natural, a green tint is produced; whereas, if foreign matter has been introduced, the wine assumes various other colors upon the addition of the alkali.[V]
The indications furnished by the above test are rendered valueless, if the wine has been artificially colored by the addition of the coloring matter of grape-skins; but the execution of this fraud would require some knowledge of chemistry, and fortunately adulterators, as a class, are deficient in this branch of science.
Another method for detecting the addition of water is based upon the fact that fermented liquors do not contain air in solution, but only carbonic acid; whereas, water dissolves oxygen and nitrogen. It is executed as follows:
The wine to be tested is placed in a flask, the delivery-tube of which is also filled, and heated; the evolved gas being collected in a tube filled with mercury. In case the wine is pure, the disengaged gas will be completely absorbed by potassa; if, on the other hand, water has been added, an unabsorbed residue, consisting of oxygen and nitrogen, will remain.
This test is useless in case water, through which a current of carbonic acid gas has been passed for a considerable time, has been employed. Under these circumstances, however, the presence of the gas would probably be detected by the taste of the wine, as well as by the estimation just mentioned, since the sample would invariably contain a larger proportion of the gas than the standard with which it is compared; indeed, it would be almost impossible to prepare a solution which contained exactly the proportion of carbonic acid ordinarily present in wine.
It remains to mention the methods employed in determining the amount of alcohol and cream of tartar contained in wine.
The alcometrical method usually employed is based upon the difference in density possessed by pure alcohol and by mixtures of alcohol and water. Gay-Lussac has proposed an areometer (alcoholmeter), provided with a scale which directly indicates the proportion of alcohol contained in a mixture. As the indications furnished by this instrument vary with the temperature, and the scale is constructed on the basis of a temperature of 15°, a correction of the results obtained is necessary if the determination is made at other temperatures. Gay-Lussac has compiled a table which indicates at once the required correction; the following formula can also be used: x = c ± 0.4 t, where x is the quantity of alcohol present in the sample; c the degree indicated by the alcoholmeter, and t the number of degrees differing from the temperature of 15°: the second member of the formula is subtracted from, or added to the first, as the temperature at which the estimation is made is greater or less than 15°.[W]