in countries other than China and India. The comparative failure of tea-growing in some countries has been attributed not so much to climate and soil as to the want of skilled labour.

According to the "Encyclopædia Britannica," the annual consumption per head of the population in the United Kingdom is 36 ounces. In England the consumption is 40 ounces, in Scotland 35 ounces, and in Ireland 23 ounces per head.

CHEMICAL COMPOSITION.

Tea has been the subject of numerous investigations as to the nature and quantity of its several constituents. There has been a certain measure of agreement in the statements which treat of the kind of substances which form the bulk of the tea leaf, but a very great diversity exists in the results stated to have been obtained by different chemists with regard to the quantities in which these are present. This is especially true if we include the earlier investigations on the subject, the results of which, with regard to some of both the organic and mineral constituents, have not been confirmed by the more recent researches. The differences may partly arise from the various meanings which it is possible to attach to some of the terms in which the analyses are stated; such as, for example, "Extractive," "Gum," "Sugar," "Tannin," and "Albumin." It may be

said that the only organic constituent of tea which has been completely isolated and identified is the alkaloid theine, and this is no doubt due to the facility with which it crystallizes.

The organic substances found to exist in tea are a volatile oil, to which much of the characteristic odour of tea is due, theine, tannin, an albuminous body, gum or dextrin, pectin, cellulose, chlorophyll, and resin.

The following results were obtained from the analysis of a Congou Tea at 2s. 10d. and Young Hyson at 3s. per lb.

They were selected as being fair representatives of black and green teas.

Oil of Tea.-The essential oil of tea is present in very small quantity. It has a specific gravity less than water, is of a yellowish colour, and readily passes into the form of a resin by exposure to the air. It possesses the peculiar taste and smell of tea, and has very potent stimulating properties. Taken in rather large quantities, the oil is said to produce headache and giddiness.

The peculiar odour of tea is mostly developed during the process of manufacture. It is more than doubtful whether it arises solely from a definite body pre-existing in the tea, as we have found that the flavour of black tea was produced, by heating for some time to a temperature of 212° F. (100° C.), a portion of an extract of green tea from which the oil or resinous matter had been removed.

Theine, C, H, N, O,-This is the alkaloid of tea.

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The pro

portion in which it is present was for some time greatly underestimated by chemists. More recent analyses, however, show a greater quantity. Stenhouse has found from 105 to 41 per cent.; Peligot, from 2°3 to 4°1 per cent.

In some recent analyses made by ourselves we obtained the following amounts of theine from 100 grains of the tea dried at 212° F. (100° C.):

Theine is very rich in nitrogen, of which it contains nearly 29 per cent. Albumin and similar substances contain only from 15 to 16 per cent.

It is to theine, chiefly, that the beneficial and stimulating properties of tea are ascribed, aided, no doubt, by the peculiar volatile principle present in the prepared leaf. Theine exists in combination with tannin in tea, and it is an impure compound of these substances which precipitates on allowing a rather concentrated hotwater solution of tea to cool. Theine crystallizes from water in the form of long needles of a white and silky lustre, containing one atom of water of crystallization. It sublimes at 365° F. (185° C.), and an attempt has been made to take advantage of this property to estimate the amount of theine in tea, but without any marked success. It dissolves rather freely in hot water, less so in cold water and alcohol, and with still greater difficulty in ether. It is altered by boiling with nitric acid, the product forming, with vapour of ammonia, a coloured substance which resembles murexide, produced in a similar way from uric acid.

Albumin or Vegetable Casein.-This substance exists almost entirely in the insoluble form in tea. A small quantity is dis

solved out with water, but the amount is less than 1 per cent. Like ordinary casein and coagulated albumin, it is dissolved by alkalis; but its separation by this means from the cellulose of the leaf is unsatisfactory.

The cellulose of tea is readily acted on by the fixed alkalis, so that the albumin can be only partially recovered in an impure state. The amount of this substance may be more accurately determined by thoroughly exhausting the leaf, first with alcohol and then with water, and estimating the nitrogen in the portion of the leaf remaining insoluble, reckoning the quantity so obtained as being all derived from albumin.

When the nitrogen, associated with the cellulose in the form of vegetable albumin, is deducted from the total amount of nitrogen found in the leaf, a quantity remains which cannot be accounted for by any proportion of theine which has as yet been fairly obtained from tea. The alcoholic extract, therefore, either contains a larger amount of theine than has been recovered from it, or there is present a quantity of another and undetermined nitrogenous substance.

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Gum or Dextrin.-Substances under the indefinite term of gum are stated by chemists to be present to the extent of from 5 to 9 per cent. We have found, however, in samples of black and green teas, the analyses of which are given above, that dextrin, arabin, or similar gum, convertible into sugar by sulphuric acid, was practically absent. It is true that about 1⁄2 per cent. of a gum corresponding to dextrin was found in the green tea; but unless the Chinese are exonerated from the suspicion of using such a gum in making up green teas, it is open to question whether even this small proportion is natural to the leaf.

Pectin, etc.-The characteristic gummy matter of tea appears to be pectin and pectic acid. It is obtained in considerable purity from the water extract after the tea has been well exhausted by alcohol. It is precipitated by alcohol in presence of hydrochloric acid as a transparent jelly, the reactions of which, on

subsequent treatment with acids and alkalis, are those of pectin and pectic acid.

Sugar. Neither of the two descriptions of tea gave any indication of sugar. The tannin of the green tea gave, after boiling with a little dilute mineral acid, 133 per cent. of glucose, indicating that a portion of it existed as a glucoside. Under similar conditions the tannin of the black tea gave no sugar.

Tannin. This is the most abundant substance found in the soluble part of the tea-leaf. Although in some degree it answers to ordinary gallo-tannic acid in its reactions, yet, from its instability and the modifications it undergoes under chemical treatment, we are inclined to the opinion that it differs from that acid in some important respects.

Chlorophyll and Resin.-Tea contains a small quantity of certain substances soluble in ether and benzol, and insoluble in water. These chiefly consist of chlorophyll and resinous bodies. It is probable that the amount obtained from tea is greater than what was originally present in the leaf, as some of the tannin and other constituents are liable to be changed by oxidation into a resinouslike substance.

Cellulose. The cellulose or woody fibre, which is insoluble in water, forms a considerable proportion of the tea-leaf. After extracting all the soluble constituents of the tea with water, there are left associated with the cellulose nearly all the albumin, part of the ash, and a little of the colouring matter. These cannot be well separated without loss of cellulose, the estimation of which has consequently to be determined by difference.

Ash. The following table exhibits the composition of the ash of seven descriptions of tea, including two qualities of Congou.