RHUBARB. 



When the refidue, after the action of water, is digelted 

 in muriatic acid, and folution of ammonia added in excefs, 

 the liquid becomes milky, and depofits oxalate of lime. 

 What remains confiits of woody matter, a fmall portion of 

 alumen, and filex. Of the fpecimens which we examined, 

 one drachm of the Ruffian rhubarb yielded twenty-fix grains 

 of the oxalate, while the fame weight of Eaft Indian yielded 

 only eighteen grains. 



From the refults of the above experiments, rhubarb ap- 

 pears to contain a large portion of extractive matter, a fmall 

 portion of refin, mucus, tannin, gallic acid, a colouring 

 matter, oxalate of lime, and minute proportions of alumen 

 and filex. They fhew that the two varieties differ from 

 each other in feveral refpefts. The Ruffian contains more 

 tannin, oxalate of lime, and refin ; the Chinefe more ex- 

 tractive and gallic acid. But the purgative principle is (till 

 unafcertained, although it appears to be combined with the 

 extractive, and hence is folubls in water. 



The yellow colour of rhubarb, it is faid, is much lefs 

 deftructible than many other vegetable yellows. Aqua 

 fords, and other acids which deftroy the colour of faffron, 

 turmeric, &c. make no change in that of rhubarb, or at 

 moft render it only turbid. Volatile fpirits heighten the 

 colour, and incline it to red. Fixed alkaline falts have this 

 effect in a greater degree. Mr. Model affirms that a con- 

 fiderable quantity of felenites is contained in rhubarb. In 

 one experiment lie obtained fix ounces of felenites from four 

 pounds of rhubarb ; and in the other, no lefs than an ounce 

 of felenites from two ounces and five drachms of old rhu- 

 barb. Rozier'a Journal for July, 1 77 5. 



Rhubarb is a mild cathartic, and commonly confidered 

 as one of the fafeft and moft innocent of the fubftanccs of 

 this clafs. Befides its purgative virtue, it has a mild aftrin- 

 gent one, difcoverable by the tafte, and by its ftriking an 

 inky bheknefs with chalybeate folutions : hence it is found 

 to ftrengthen the tone of the ftomach and inteftines, to leave 

 the belly coftive, and to be one of the moft ufeful purga- 

 tives in diarrhoeas, dyfenteries, and all diforders proceeding 

 from a debility and laxity of the fibres : it is frequently 

 given with a view to this ftomachic and corroborating virtue, 

 rather than to its producing any confiderable evacuations. 

 It tinges the mine of a high yellow colour. Rhubarb in 

 fubftance purges more effectually than any preparation of 

 it : the dofe is from a fcruple to a drachm. From 3j to 5 fi 

 of the powdered root opens the bowels freely ; and from 

 grj. vi to grs. x may be given for a dofe, when its ilo- 

 machic properties only are required. By roailing it with a 

 gentle heat, till it becomes eafily friable, its cathartic power 

 is diminifhed, and its aftringency fuppofed to be increafed. 

 The purgative virtue of rhubarb is extracted more perfectly 

 by water than by rectified fpirit ; the root remaining after 

 the action of water is almoft, if not wholly, inactive ; 

 whereas, after repeated digeltion in fpirit, it proves itill 

 very confiderably purgative : when the rhubarb has given 

 out to fpirit all that this menftruum can extract, it ftill im- 

 parts a deep colour, as well as a purgative impregnation, to 

 water. A drachm of the extract, formed by infpiflating 

 the watery infufion, is not more efficacious than a fcruple 

 of the root in fubftance ; but half a drachm of the extract, 

 formed from the fpirituous tincture, proves moderately pur- 

 gative, though fcarcely more fo than an equal quantity of 

 the powder. The fpirituous extract dill'olves almoft wholly 

 in water ; and hence the tincture, like the fpirituous infu- 

 fions of moft other vegetables, does not turn milky on being 

 mixed with aqueous liquors : of the watery extracts fcarce 

 above one -fourth is diffolved by rectified fpirit, and the part 



that does not diifolve proves more purgative than that which 

 does. Hence it appears, that rhubarb contains much more 

 gummy or mucilaginous than refinous matter ; and its pur- 

 gative quality feems to refide chiefly in a combination of 

 gummy and laline matter. 



" The qualities of this root," fays Dr. Cullen (Mat. 

 Med. vol. ii.), " are that of a gentle purgative, and fo 

 gentle that it is often inconvenient by reafon of the bulk of 

 the dofe required, which in adults mull be from half a 

 drachm to a drachm. When given in a large dole, it will 

 occafion fome griping, as other purgatives do ; but it is 

 hardly ever heating to the fyftem, or fhews the other effects 

 of the more draftic purgatives. The purgative quality is 

 accompanied with a bitternefs, which is often ufeful in re- 

 ftoring the tone of the ftomach, when it has been loft ; and 

 for the moft part, its bitternefs makes it fit better on the 

 ftomach than many other purgatives do. Its operation 

 joins well with that of neutral laxatives ; and both together 

 operate in a leffer dofe than either of them would do fingly. 



" Some degree of ftipticity is always evident in this medi- 

 cine ; and as this quality acts when that of the purgative 

 h3s ceafed, fo in caies of diarrheca, when any evacuation is 

 proper, rhubarb has been confidered as the moft proper 

 means to be employed. I mull, however, remark here, 

 that in many cafes of diarrhcea, no further evacuation than 

 what is occafioned by the dileafe is neceffary or proper. 

 The ufe of rhubarb in fubftance for keeping the belly re- 

 gular, for which it is frequently employed, is by no means 

 proper, as the aftringent quality is ready to undo what the 

 purgative had done; but 1 have found that the purpofe 

 mentioned may be obtained by it, if the rhubarb is chewed 

 in the mouth, and no more is fwallowed than what the faliva 

 has diffolved. And I muft remark, in this way employed it 

 is very ufeful to dyfpeptic perfons. Analogous to this is the 

 ufe of rhubarb in a lolution, in which it appears to me that 

 the aftringent quality is not fo largely extracted as to 

 operate fo powerfully, as when the rhubarb was employed 

 in fubftance." 



The operation of rhubarb is quickened by the addition of 

 neutral falts and calomel, the purgative powers of which it 

 alfo reciprocally augments ; fo that a compound, formed of 

 fmall portions of rhubarb and a neutral fait or calomel, acts 

 with more certainty, and quicker, than large dofes of either 

 feparately taken. Rhubarb is particularly adapted for the 

 greater number of cafes of diarrhcea, as it evacuates any 

 acrid matter that may be offending the bowels, before it 

 acts as an aftringent. A3 a ftomachic and aftringent, it is 

 ufefully given in dyfpepfia, hypochondriafis, and in a 

 weakened relaxed ftate of the bowels, combined with ginger, 

 nutmeg, foda, or bitters. Externally its powder is fome- 

 times fprinkled over ulcers, to afiift their granulation and 

 healing. 



Its officinal preparations are as follow : -viz. Infufum 

 rheiy Lond. Pharm., infufion of rhubarb, prepared by ma- 

 cerating for two hours a drachm of rhubarb root, fliced, 

 with half a pint of boiling water, in a lightly covered veilel, 

 and draining it. 



Infufum rbei palmali, Edinb. Pharm., infufion of rhubarb, 

 prepared by macerating half an ounce of bruifed rhubarb 

 root with eight ounces of boiling water, in a covered veffel, 

 for twelve hours, and then adding one ounce of fpirit of 

 cinnamon, and draining it. Theie infufions differ chiefly 

 in their llrength ; but that of the Edinburgh difpenfatory is 

 rendered pleafanter by the addition of the fpirit. The co- 

 lour of both is a reddifh-brown, much deepened by the ad- 

 dition of alkalies. ' The following fubftanccs either occafion 



precipitation, 



