Mr. Bodmer considered the sample to probably contain 10 per cent. beef stearin, 25 cocoa-fat, 45 cotton-seed oil, 20 per cent. lard.* Since the above is a typical case of adulterated lard, it may be useful to examine the figures in detail. First, the melting-point affords no indication of impurity. The specific gravity is higher than usual, and is suspicious. The Reichert test gives decided indications of more volatile acid than in lard, and in itself points clearly to cocoa oil; the saponification figure is fairly high, but not beyond genuine lards. The iodine number, although not very high, is yet higher than in the majority of genuine lards; Bechi's nitrate of silver gave a decided reaction indicative of cotton-seed oil; lastly, beef stearin crystals were discovered, and the ether deposit weighed 37 mgrms., which, for a lard of 38° melting-point, according to Stock, is never found in genuine samples. Hence the diagnosis of a mixture of beef stearin, cotton-seed oil, cocoa oil, and lard is perfectly justified, and the only thing open to doubt is the quantities which have been assumed to be present. As there are considerable variations in the composition of genuine lard, all calculations of the amount of the fats or oils entering into the mixture are liable to error. BIBLIOGRAPHY. BENEDIKT, R.-Chemical Analysis of Oils, Fats, and Waxes, revised and enlarged by Dr. J. Lewkowitsch, F.I.C., F.C.S. Lond., 1895. GLADDING, T. E.-Examination of Lard for Adulteration. Analyst, Feb., 1889. STOCK, W. F. KEATING.-On the Estimation of Beef-fat in Lard. Analyst, Jany., 1894. WILEY, H. W.-Lard and Lard Adulteration. U. S. Department of Agricul., Bull., No. 13, Washington, 1889. * Analyst, 1895. TEA. § 193. Varieties of Tea.-Tea is the dried leaf of different species of Thea, a section of the genus Camellia. The botanical varieties do not appear to be numerous. Thea Bohea, T. viridis, and T. sinensis, all Chinese plants, Thea Assamica, indigenous to Assam, and one or two hybrids, are the principal plants from which the numerous teas of commerce are derived. The difference depends on the selection of young or old leaves, and special treatments in drying and otherwise preparing the leaf, rather than on essential botanical variation. The varieties of tea imported into this country are extremely numerous; but seldom does any one of them reach the consumer unmixed, for the wholesale tea merchants carefully improve their teas by " blending." The most common sorts are-Gunpowder, Hyson, Congou, Capers, and Indian tea. Of these, the Gunpowder and Hyson are dried at a higher temperature than the others, and contain less hygroscopic moisture. The Capers may be generally told by the leaves being rolled up into little lumps with starch or gum; as a class, they are much adulterated, and, in fact, can hardly be called genuine tea. Besides these, there are a number of special teas, some of a very high price, and imported in a state of great purity; but such teas are used almost entirely for mixing or blending.* They are known under the names of Moyone, Moyone gunpowder, * In Cooper's travels ("Travels of a Pioneer of Commerce," by T. T. Cooper, London 1871), there is an interesting account of the brick tea used in Thibet, some of which may find its way to Russia, but none, probably, to this country. It is the staple produce of the city and district of Yatzow, and the tree from which it is prepared attains not unfrequently the height of 15 feet. It has a large coarse leaf, and is cultivated with little care, growing along the borders of fields and homesteads. There are three qualities of the tea: the first is gathered in June and July, when the leaf is about an inch long. It is spread out in the sun to dry slightly, then rolled in the hand until the sap begins to exude, and when in this state made up into balls, and laid on one side to ferment. After fermentation, it is pressed into wooden moulds, and dried by charcoal fires. The bricks on their removal from the moulds are enveloped in yellow paper covers, bearing a Government stamp and the trade mark of the exporter, and then they are packed in baskets four feet long, made of the thin strips of the bamboo. The bricks thus packed form a packet of tea," and weigh about 20 lbs. ; at Llássa, this quality of tea sells for 4s. Sd. per lb. The second_variety consists of the older and yellower leaves which, when exported to Lethang and Bithang, sell for 1s. 6d. per lb. The third variety is merely chopped twigs stuck together by rice water, and is only used in the neighbourhood of Ta-tsian-too, where it is sold at 9d. per lb. 66 Oolong, Mannuna Kaisow, scented Pekoes, Indian Souchong, Assam, Java, &c. The names by which the teas of commerce are most familiar to the public are simply "green" and "black," which differ merely in accordance with the method of preparation followed. Green tea is prepared from young leaves, which are roasted over a wood fire within an hour or two after being gathered. The black tea leaves, on the other hand, are allowed to lie in heaps for ten or twelve hours after they have been plucked, during which time they undergo a sort of fermentation; the leaves then pass through certain processes, and are slowly dried over charcoal fires. $194. Structure of the Tea Leaf.-The border is serrated nearly, though not quite, up to the stalk (see fig. 40). The primary TEA PLANT veins run out from the midrib almost to the border, and then turn in, so that a distinct space is left between them and the border. A section through a tea-leaf is difficult to make successfully; but when this is accomplished, it will be seen that the upper and lower epidermis are very similar in thickness and structure, both being formed of a single row of oblong thickwalled cells, the upper epidermal layer being also covered with a cuticle. The mesophyll, or parenchyma of the leaf, contains two kinds of cells, the one being a very regular single or double row, filled with chlorophyll, just beneath Fig. 40. the upper epidermal layer, whilst a spongy parenchyma, containing large spaces, occupies the rest of the leafthickness. There are also cells containing crystals, and, lastly, there are the peculiar structures called "idioblasts" (see a, fig. 41). Idioblasts are long, tough, tenacious, branched cells, which seem to act as pillars, or beams, keeping the two layers of the leaf apart; they do not occur in any other leaf with which the tea-leaf is likely to be confused, so that their presence would indicate tea, their absence would point to foreign leaves. A very convenient method of detecting idioblasts is given by Moeller*:-Small fragments of the leaf are warmed in a very strong solution of caustic potash, and then placed under the thin covering glass and pressed firmly (see fig. 41). The surface-view of the leaf is different on both sides; The hairs of tea are very characteristic, but not constantly found; they disappear from old leaves, but the under-surface of young leaves is always thickly beset with them. The hairs are 1 mm. long and about 015 mm. broad (see b, fig. 41). Fig. 41. $195. Chemical Composition of Tea.-The constituents of tea are-Essential oil, theine, boheic acid, quercetin, tannin, quercitannic acid, gallic acid, oxalic acid, gum, chlorophyll, resin, wax, albuminous, woody, and colouring matters, and ash. The essential oil of tea varies from 0-6 to 1 per cent. It is citron-yellow, lighter than water, has a strong odour of the tea plant, solidifies easily by cold, and resinifies on exposure to air.† Theine, Caffeine, CH10N4O-This alkaloid was first separated in an impure condition by Runge, from coffee berries, in the year 1820. It was found by Corput and Stenhouse also to be a constituent of the leaves of the coffee tree. Oudry in 1827, finding it in various species of tea, named it "Theine," and Oudry's "Theine" Mulder and Jobst showed, in 1838, to be identical with caffeine. The alkaloid has also been discovered in guarana, maté, and the kola nut, by Martius, Stenhouse, and Attfield respectively. Theine crystallises from an aqueous solution with 1 atom of water; from ether, in an anhydrous state. It sublimes in minute dots at 78°.8, in crystals at 79°4 (175° Fahr.), and above. The sublimate consists of microscopic needles: that Mikroskopie der Nahrungs- u. Genussmittel. Berlin, 1886. + A fixed oil, serving many purposes in China, is extracted from the seeds of the tea plant. It is citron-yellow, specific gravity 0.927, and is composed of one part of stearin and one of olein. The subliming point given by Pelouze, 178°, and by Mulder, 184° 7, which is first produced is of extremely fine, light elements; after a little time, at such temperatures as 120°, the crystals become longer and larger. The melting point of theine is some Fig. 42.-EPIDERMIS OF TEA LEAF, × 300. a under, b upper surface. where between 177° and 228°. Theine possesses a slightly bitter taste, but is without odour. According to a recent research, the solubility of theine in different solvents is as shown in Table XXII. 8 8 8 Theine forms numerous salts of definite composition-the hydrochlorates, CH10N4O2, HCl and CH10N402, 2HC1; a platinum compound, CH10NO, HCl, PtCl; a chloride of gold compound, CH10N402, HCl, AuCl; a chloride of mercury compound, CH, NO, 2HgCl; an argentic nitrate compound, CH10N402, AgNO,, and many others. Some of these, such as 8 8 must have been obtained by extremely faulty methods. If a little theine is placed between two watch-glasses on the water-bath, the almost instantaneous rise of crystals to the upper glass will at all events show that the subliming point is below 100°. See the author's paper, "Temperature at which the Alkaloids sublime," Journal of Chemical Society, 1878. * The salts with hydrochloric, hydrobromic, and sulphuric acids are decomposed by water. The sulphate crystallises with difficulty, the hydrobromide well. Theine forms compounds with sodium acetate, citrate, sulphate, chloride, benzoate, cinnamate, and salicylate. Theine gives no precipitate with potassium mercuric iodide, and it has a neutral reaction. See Tanret. J. Pharm. Chim. [5], v. 591-595. |