Three varieties of rhubarb are known in the shops, named from the places whence we receive them; Russian rhubarb, Turkey rhubarb, and East India or Chinese rhubarb. The two first resemble one another in every respect, appearing to be the root of the same species of Rheum prepared in the same mode; and although the East Indian is seemingly the root of a different species, yet we are informed by Dr. Rehman1 that it is the same, only prepared with less care.

All the rhubarb of commerce, known under the names Turkey or Russian, grows on the declivities of the chain of mountains in Tartary, which stretches from the Chinese town Si-ning to the Lake Koko Nor, near Thibet, the source of the river Chou-cho. The soil is light and sandy; and the Buchanans assert that the best grows in the shade, on the southern side of the mountains. Rhubarb, however, is also cultivated in China, in the province of Shen-see, where it is called haihoung. In Tartary the roots are taken up twice a year, in spring and in autumn2; and after being cleansed and decorticated, and the smaller branches cut off, the body of the root is divided transversely into pieces of a moderate size, which are placed on tables, and turned three or four times a day, during five or six days. A hole is then bored through each piece, by which it is hung up to dry, exposed to the air and wind, but sheltered from the sun. In Bontom they are hung up in moderately heated drying rooms. In about two months, the roots have lost seven parts in eight of their weight3 and are fit for the market.

In China the roots are not dug up till winter4; and the cultivators, after cleaning, scraping off the bark, and cutting them, dry the slices by frequently turning them on stone slabs heated by a fire underneath; after which the drying is completed by hanging them up in the air, exposed to the greatest heat of the sun.5 As soon as the rhubarb has been dried where it is grown, it is convened to Si-ning, where it is again cleaned and aired: and, after being cut into smaller pieces and sorted, a large hole is drilled through that intended for the Russian market, in virtue of the contract made with the Russian government, for the examination of the heart of the pieces. It is then packed up in camel's hair sacks, and conveyed to Mac-ma-tchin, where it is examined previously to its being transported to Kiachta. The whole of the trade in rhubarb in China is carried on by one Bucharian family, which has enjoyed the monopoly since 1772; and it is even by the agents of this family that it is sold to the English at Canton. This Bucharian family resides at Si-ning Fu, a town on the frontiers of Thibet, about 3,000 versts from Kiachta, the town on the Russian frontier where the rhubarb is purchased on the account of the Russian government.

Part of the Tartarian rhubarb is carried to Turkey through Natolia; thence the name Turkey rhubarb: but the greater part is conveyed by the Bucharians to Kiachta, where it is examined by a Russian apothecary. The best pieces only are selected and sent to Petersburgh. The pieces are roundish, perforated with a large hole; they are of a yellow or reddish colour on the outside, somewhat soft and friable, and, when broken, exhibit many diverging streaks of a beautiful bright red colour. Agreeably to the contract with Russia, all the rhubarb which is rejected must be burnt; and even that which is approved must undergo another cleaning before it is finally packed up for St. Petersburgh.1

1 The best treatise on the Commerce of Rhubarb, and from which much of the information contained in this article has been taken, is from the pen of Dr. Rehman. Vide M6m. de la Societe Imperiale des Nat. de Moscow, 1809, t. ii. p. 126.

2 Bell's Travels.

3 Bath Papers, iv. 175. 4 Bath Papers, ii. 249.

5 It is in the process of drying the roots that the British cultivators of rhubarb are supposed to fail. Baume proposes to steep the roots in water, to deprive them of their gummy matter, before drying them; then to lay them upon twigs in the open air for twelve hours, and lastly to place them in a stove heated to 120°, till they are dried. When sufficiently dry, the wrinkles must be rasped out, and the pieces shaken together in a barrel, turned on an axis, for half an hour, which covers them with a fine yellow powder formed by their attrition.

The Chinese rhubarb, at least what we receive under that appellation, is conveyed to Canton, and there purchased by the East India Company's agents, who purchase all qualities; whence it is brought to this country by sea. It is in oblong, round, and flat pieces, sometimes perforated, but with a smaller hole than the Russian rhubarb; considerably heavier, more compact, and less friable than the former kind; of a brownish yellow colour on the outside; and, when broken, the fracture is hackly, appears of a dull colour, and variegated with yellow, pink, and white. The flat pieces are prepared by rasping the spongy alburnum from the round pieces; and thus prepared the rhubarb sells at one third more than the unrasped root. Both kinds are brought to this country in cases and chests.2

1 At this examination, each piece is struck with a small mallet, to detach from it any impurities or decayed parts.

2 Rhubarb sometimes appears worm-eaten; a circumstance which arises from its being eaten, in its dry state, by a small beetle, Sinondendrum pusillum.-Kirby and Spence's Entom, vol. i. p. 252.

Qualities. - Good Russian or Turkey rhubarb has a peculiar, somewhat aromatic odour, and a bitter, slightly astringent, subacid taste; feels gritty between the teeth when chewed, and tinges the saliva of a bright yellow colour. It breaks with a rough hackly fracture, is easily pulverized, and affords a powder of a bright buff-yellow colour. It should not be porous, but rather compact and heavy. Water at 212° takes up 24 parts in 60, forming an infusion of a pale brown colour, nearly clear, reddening litmus paper, and striking a deep brown with alkalies. Alcohol extracts 2.7 from 10 parts, and gives a tincture of a rich golden colour, which reddens tincture of litmus, is not altered in its transparency by the addition of water, and strikes a blackish olive hue with solution of sulphate of iron, but no immediate precipitate falls. Sulphuric ether takes up 1.5 in 10 parts of this rhubarb; the tincture is of a golden yellow hue, and when evaporated on water leaves a thin pellicle of yellow resin, and abundance of extractive dissolved in the water, combined, however, with tannin.

According to the analysis of M. Henry, it contains a yellow colouring matter, a bland oil, fecula, a small quantity of gum, tannin, lignin, oxalate of lime, supermalate of lime, sulphate of lime, a salt of po-tassa, and oxide of iron.1

East Indian or Chinese rhubarb has a stronger odour, tinges the saliva of an orange hue, and is more nauseous to the taste than the Turkey; breaks with a more compact and smoother fracture; and affords a powder of a redder shade. Water takes up 30 parts in 60; the infusion is not so deep-coloured as that of Russian rhubarb, is more turbid, reddens also litmus paper, and is browned by alkalies. Alcohol extracts 4 parts in 10; the tincture is of a much deeper colour, and brownish; gives a deeper red to litmus tincture; is rendered slightly turbid by the addition of water; and strikes a green, not blackish olive, with sulphate of iron, which it also quickly and copiously precipitates. Ether takes up 2 parts in 10; the tincture is deeper coloured; and, when evaporated on water, affords the same results as the former kind, except that the compound of tannin and extractive is more soluble.

The infusion of Chinese rhubarb is more copiously precipitated by solution of isinglass than that of the Russian. Infusion of yellow cinchona bark throws down a copious greenish precipitate from infusion of Russian rhubarb, and a less copious, but more dense, bright yellow precipitate from that of Chinese rhubarb.

The following Tables show the effects of re-agents on the aqueous infusions of the two varieties of rhubarb.

1 Bulletin de Pharn. t. vi. p. 87.

Table I. Precipitates Formed By Acids, Alkalies, And Neutral Salts

Table II. Precipitates Formed By Solutions Of Metallic Salts

When the residue, after the action of water, is digested in hydrochloric acid, and solution of ammonia added in excess to the solution, the liquid becomes of a deep purple colour, then somewhat milky, and deposits oxalate of lime. What remains consists of woody matter, a small portion of albumen, and silex. Of the specimens which I examined, one drachm of Russian rhubarb yielded twenty-six grains of the oxalate, while the same weight of East Indian yielded eighteen grains : M. Henry procured only 30 per cent., and Schrader not more than 4.5 !

From the results of my experiments, rhubarb appears to contain a large portion of extractive matter, a very small portion of resin, mucus, tannin, or rather a principle analogous to it, gallic acid, a colouring matter, much oxalate of lime, and minute proportions of alumen and silex.1 According to the analysis of M. Henry, the Russian and Chinese rhubarb contain of resin and extractive-R. 44. C. 39.35. + gum, R. 5.5. C. 6. + starch, R. 4.8. C. 12.86. + albumen, R.-C. 0.2. + oxalate of lime, R. 29.98. C. 32,8.+ lignin, R. 10.62. C. 11.2. From this and other analyses no opinion can be formed of the active principle of rhubarb.

The preceding tables show, that the two varieties differ from each other in several respects. The Russian contains more tannin, oxalate of lime, and resin than the Chinese; the Chinese more extractive and gallic acid than the Russian. Besides these components, M. Henry found a fixed oil soluble in ether and alcohol, an amylaceous matter, supermalate of lime, sulphate of lime, and a salt with a base of potassa.2 But the purgative principle is still unascertained, although it appears to be combined with the extractive, and hence is soluble in water.3 M. Hornemann ascribes it to a new proximate principle which he has discovered, and named Rheumine. The colouring principle is the Rabarbarine of Caventou.1

1 According to some experiments published by Mr. John Henderson, in the Annals of Philosophy, rhubarb is supposed to contain also a peculiar acid, to which he has given the name of Rheumic; but M. de Lassaignes has proved, that this is the oxalic acid : which agrees with the result of our analysis. It is remarkable, that Mr. Brande, in an analysis of rhubarb, published in the Quarterly Journal of Science, vol. x., does not notice either oxalic acid or any oxalate as being contained in this root, although they have been found and are mentioned by every other analyst who has examined rhubarb. But it is still more extraordinary, that Mr. Brande has asserted, that "no chymical investigation into the nature of rhubarb, if we except a few experiments upon it, given in Neumann's Chemistry," had been made prior to his own; while every one acquainted with pharmaceutical chymistry knows that (not to mention my analysis) it has been examined by Scheele, Bayen, Deluval, Vauquelin, M. Clarion, De Lassaignes, M. Henry, Heyer, Schrader, etc.; all of whom mention oxalic acid and oxalate of lime among its components.

2 Journal de Pharm. torn. iv.

3 M. Najni of Milan, imagines he has discovered a new alkali in rhubarb. Sce account of the experiments in Brande's Journ. No. xxxii. p. 172.

Medical properties and uses.-Rhubarb is stomachic and astringent or purgative, according to the extent of the dose in which it is administered. With a view to the first-mentioned properties, it is usefully given in dyspepsia, hypochondriasis, and a weakened, relaxed state of the bowels, combined with ginger, nutmeg, soda, or bitters.

As a purgative it operates mildly, and may be given to the youngest infants. Its operation is quickened by the addition of neutral salts and calomel, the purgative powers of which it also reciprocally augments: so that a compound, formed of small portions of rhubarb and a neutral salt or calomel, acts with more certainty and quicker than large doses of either, separately taken. Rhubarb is particularly adapted for the majority of cases of diarrhoea, as it evacuates any acrid matter that may be offending the bowels, before it acts as an astringent. In some persons it causes convulsions, owing to a peculiar idiosyncracy. Externally it has been applied by friction to produce its pargative effects 9, and its powder is sometimes sprinkled over ulcers to assist their granulation and healing. It colours the urine in the space of twenty minutes after it is taken; and may be detected by the aid of an alkali. It disappears after an hour or two, but re-appears, owing to a second absorption from the colon.3 Bradner Staart also affirms that it can be detected in the urine after using a bath impregnated with it!

The Chinese use it medicinally; but they chiefly employ it to colour a spirituous liquor.

Rhubarb is given in a variety of forms (see Preparations), but its purgative properties are most powerful in substance. From Э j. to 3 ss. of the powdered root opens the bowels freely; and from grs. vi. to grs. x. may be given for a dose, when its stomachic properties only are required.

Officinal preparations.-Infusum Rhei, L. E.D. Vinum Rhei, E. Tinctura Rhei, E. Tinctura Rhei composita, L. D. Tinctura Rhei et Aloes, E. Tinctura Rhei et Gentianae, E. Extractum Rhei, L. D. Pilulae Rhei compositae, L. E.