greenish-white covering, a thick, strong shell, and a small kernel or seed. The fruit, gathered when not yet quite ripe, steeped for some time in lime water or alkaline ley, and then pickled in brine, is sold as the olive of the grocer's shop.

The finest, or virgin oil, is obtained by crushing the ripe olives. The ordinary oil of commerce is prepared by covering the olives with hot water and expressing; and the oil of lower quality separates spontaneously from the water used for separating the ordinary oil. Lastly, the impure oil (fermented oil), always musty tasted, is expressed from olives which have been allowed to ferment. finest oil comes from Provence and Florence, sometimes also from Genoa and Lucca. The common sort, imported into this country under the name of Gallipoli oil, is brought from Naples; and that from Sicily and Spain, which is generally fermented oil, is the worst of all.

The

Fine olive oil has a pale, greenish-yellow tint, and keeps long without becoming rancid; it is fresh and without odour. Density 911 at 77° Fahr., at the temperature of 38°, a considerable part of it solidifies in white crystalline grains. It slowly absorbs oxygen from the air, and becomes thick and rancid.

Adulterations of Olive oil.-This fluid is much subject to be adulterated with poppy-seed oil, rape-seed oil, and other cheap oils. The density of the fluid is thus considerably increased, so that the adulteration may be detected, and its amount estimated by ascertaining the specific gravity of the mixture. But the best method to effect this purpose is that of Mr. Paulet. When pure olive oil is mixed with a solution of mercury in pure boiling nitric acid, the whole becomes in a few hours a firm fatty mass,

from the action of the hyponitrous acid in the solution. But if even so little as 5 per cent. of any other oil be present, the consolidation is much less complete, and slower; and if the proportion amount to 12 per cent., the foreign oil floats on the surface of a pulpy mass, for several days, before showing any tendency to consolidate.1

' Dr. Christison's 'Dispensatory,' second edition, p. 660.

CHAPTER IV.

ON FERMENTED BEVERAGES AND THEIR

ADULTERATIONS.

WINE, BEER, SPIRITS, VINEGAR.

WHEN a solution of sugar, in water, is mixed with a ferment (yeast, &c.), and exposed to a temperature of from 70° to 80° Fahr., it will very soon begin giving off carbonic acid gas, and acquiring a certain proportion of alcohol, both substances resulting from the decomposition of the sugar pre-existing in the liquid. This phenomenon is called the alcoholic fermentation. Wine, beer, and spirits are obtained by the process just mentioned; but spirits differ from the other beverages, in as much as they are the products of the distillation of alcoholic fluids. If a liquid which has undergone alcoholic fermentation, is allowed to remain still longer, freely exposed to the atmosphere in a warm place, a further process of decomposition will be induced, called the acetous fermentation, and the liquid will be found to contain vinegar.

I propose in this chapter

1. To offer a few remarks on the chemical composition and distinctive characters of wines, beer, and spirits.

2. To give the reader such practical directions as are best calculated to enable him to make a satisfactory chemi

cal analysis of alcoholic liquors, both in reference to the nature and quantity of their constituents.

3. To show how alcoholic liquors may be adulterated, and what methods should be adopted for the detection of the fraud.

4. To offer a short account of the preparation of vinegar, its chemical composition and analysis, and to show the adulterations to which this article of diet is exposed, together with the methods for their detection.

WINE.

Wine is prepared from the alcoholic fermentation of juice of grape. All genuine wines have an acid re

action, are more or less alcoholic, and contain some sugar. Their flavour depends on the presence of certain volatile ethers. In the Philosophical Transactions' for 1811 and 1813, Mr. Brand has given tables of the strength of wine, beer, and spirits; and more recently, in 1854, Dr. Bence Jones has devoted much attention to this subject; besides ascertaining the amount of alcohol in a great number of different wines, beer, and spirits, he has determined the quantity of sugar and acid they contained.1

According to the general results obtained from Dr. Bence Jones's investigations respecting the acidity of wines, the quantity of alkali required to neutralize a measure equal to 1000 grains of water was

In Port wine (8 different qualities were examined)

In Sherry

Grains.

.

2.10 to 2.55

1 Lecture on the Acidity, Sweetness, and Strength of different Wines, delivered at the Royal Institution of Great Britain. By Henry Bence Jones, M.A., M.D., F.R.S., etc., February 1854.

2 The same different qualities were submitted to analysis for the purpose of determining the amount of sugar and alcohol they contained.

Hence, proceeding from the least acid wine to the most acid, we have: Sherry, Port, Champagne, Claret, Madeira, Burgundy, Rhine wine, Moselle.

In regard to the amount of sugar in different wines, the same distinguished physician concluded from his investigations that

The degrees in the above table are those of the saccharometer of Mr. Soleil, an instrument which will be described in the course of this chapter.

Dr. Bence Jones ascertained the strength of a great number of alcoholic fluids, by means of the alcoholometer of Geisler, which acts by the tension of the vapour of the fluid to be examined, forcing up a column of mercury. It may be stated generally that in these experiments the alcohol varied

Claret and Hock contained no sugar.