RHEUM.

817

1 .

'' 9 ii ^ 0rnu ' t matter of rhubarb (Volatile Oil ?)—In none of the analyses of rhubarbV^.Plpuion made of an odorous principle; yet such must exist. Professor Gui-Sj des Drog. t. ii. p. 569, 3 ,,,e ed.), however, ascribes the odour, colour, andi^t . mubarb to one and the same principle ; but this opinion can scarcely be cor-ki,„j s "* Ce the degrees of colour and odour bear no proportion to each other in differentkit|) e i fhubarb. The odorous principle is probably a volatile oil, but it has not^((4 .° “ een isolated. Dr. Bressy announced, a few years since, to the Academie dethat he had separated it, but the committee appointed to repeat his expe-S | Was unable to procure it by his process (Diet , des Drog. t. iv. p. 425).^ 5 in' ^^arm. Central-Blatt fur 1832, S. 237) says that the rhubarb odour is imitated2 y Xture of nitric acid, aloes, and chloride of iron. •

colouring matter of rhubarb {Rhabarberic acid, Brandes; Rheumin, Hor-7H e . Rhabarberin, Geiger; Rhein, Auctor.)—Extracted from rhubarb in powderof ether, and obtained by distilling off the greater part of the ether from the^bus procured, andleavingthe residue to spontaneous crystallization. Thecrys-Purified by repeated solutions and crystallizations in alcohol. When dry, theyr e tile form of a powder, having an intensely yellow colour, but being withoutjMl rtlar hable taste. Rhabarberic acid is unchanged in the air; heated, it fuses into% S(! 0lv fluid, which, by a continuance of the heat, becomes reddish-brown, evolvesS in^ w vapours [pyro-rhabarberic acid?], and carbonizes. It requires morehi s u '*0 parts of cold water to dissolve it, but is twice as soluble in boiling water.Sn7/ eso . lu . ble in alcohol and in ether: the solutions redden litmus. In cold oil of]. s qnd in oil of turpentine it is slightly soluble; but is much more so when*ti(l s . 1( l Ul ds are hot. It dissolves, with a dark-red colour, in sulphuric and in nitric*’tli ~ " ate r precipitates it from these solutions unchanged. Nitric acid attacks it'* Ce l)t j** difficulty. Alkaline solutions make it dark-red, and generally (lime-water' , ilh a ' dissolve it. Alum renders it dark-red. The alkaline solutions of it form,Jjitli ® ta te of lead, chloride of calcium, and chloride of barium, yellow precipitates ;bei,, u ‘Phate of copper, violet, which, after some time, becomes blue (Brandes and,s ti! e ’ Central-Blatt fur 1834, S. 607). Brandes regards rhabarberic acid

%i c act ive principle of rhubarb. Six grains of the pure acid given to a strong youngan. ailse d griping, but did not purge (Ibid, fur 1836, S. 498). Dulkis of opinion that"nciple of rhubarb is a difficultly crystallizable substance, which be termshich, by oxidation, becomes Rhabarberic acid. This acid, according to

3. 7 a pd Leber, consists of C 35 II 19 019 (Pharm. Cent.-Blatt fur 1839, S. 102-105).

matter (Tannic and Gallic Acids ).—The red veins are the seat of the** matter. This is proved by brushing the cut surface of rhubarb with a weak. oils'. a ferruginous salt: the red veins ouly undergo a change of colour. Fromki,| Ovations of Brandes, it appears that rhubarb contains gallic, as well as taunic,

^it|^i^ er principle .—Rhubarb contains a hitter principle ; but most of the substancesfcite (? Ve been announced as the hitter principle of rhubarb, under the name of capho-» Uded ^ r ° m lca< P'iu, to exhale, and viKpos, bitter ), or rhabarberin, are themselves com-mie s tWo or more principles. Thus, Pfaffs rhabarberin consists of uncrystalli-N^Srar, extractive, resin, rhabarberic acid, and tannin. Henry's rhabarberinI te 0 f °* resin and rhabarberic acid. Buchner and Herberger's rhabarberin is a mix-(Hi £ ext raetive, uncrystallizable sugar, and rhabarberic acid. Carpenter's rhabar-V^ins some rhabarberic acid (Brandes, Pharm. Cent.-Blatt fur 1836, S. 498).if es >n • a PP ear from the analysis of Brandes that the bitter principle is of the nature

I ^ Ut Buchner (Pharm. Central-Blatt f ir 1837, S. 821) admits the existencela ill r , extr active (caphopicrite), which is soluble in water and alcohol, but is inso-%i " ether. This extractive, he says, is in intimate combination with rhabarberic,>i s ,! a !id gallic • ' . ..

Ki^er.' _ _

, (J L. UI gallic acids; the compound thus formed being the resin of some chemists.

therefore, that a further examination of the bitter matter is required tof Ith Sat ' s .factorily its nature.

—A yellow, crystallizable, odourless, tasteless substance, obtaineda, j tlio r< ! ot .°f European [English ?] rhubarb. It is insoluble in cold water, ether,6 '&l>t nfi'^ e °'^ s > but soluble in 24 times its weight

Pl , — uuv ouiuo.c I.* in..,, of boiling water, and twice its

r - -■ Og, .absolute alcohol (Berzelius , Traiti de Chim. vi. 205).

of lime .—The conglomerate raphides before noticed (p. 812) are crystalsWi a a rh v f bme - They may be separated in great abundance by boiling Russian or„f ken if, U jb in water until the cohesion of the tissue is completely destroyed,of l ^ v es , coni P ose d tissue is well shaken with water, the crystals tall to the bottomflieiq : Heated to redness, they are changed into carbonate of lime. A solution

n '' ited nitric acid, or a solution obtained by boiling the crystals with a solu-

3 G