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CITRIc Ac ID osten accompanies the malic acid in tho juieoxos ituripe fruits, and it exisis in a purex forna in the juice of the lemon and lime: Doni these it is usualty extracted, thomucilaginous matter of the juice being Separated by aikohol It crystalliges in rhomboides prisms ; whicli, wheu it is pure,
nitrio acid, there is probabj a large proportion of oxygen in iis composition. The test by Whicli it is peculiarly distinguished, is the insolubie precipitate it fornas u illi lime, an earili to whicli iis assinity is such that it attracis it Dom au
I ARTARIC A cID. This acid, as it crisis in vegetabies, is usualty combined with potasti, in Such a prolaortion, lao x ever, as to leave an excess of acid in the combinatioii. Thistorius the super-tartrate of potasti, Whicli is containod in an imber of vegetable fruits. It is deposited si una illo sulcopi ille grape in iis conversi0n tuto ivine, Or in the sto v scr-
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OF THE GENERAL PRINCI LES mentation whicli the wino suffers when Lept. The acidprocured hom this sali is in tabular c Stais, transparent; they a re very Solubie in Water, the Solution when concentrat
sn important one in pharmacy, froin the numerous combinations of ii applied to medicinal use. EgNetoic A cID is obta ed froin the vegetable balsams, generat ly by the process of sublimation. It condenses instender crystals, white and brilliant. It is volatile, and iis vaporiae is inflanun te; it is very sparin y sol le tu coldwater, but abundantly in hol water; the solution on coolingdepositi g nearly the whole of the acid in prismatio crystals: it is also sol le in alkοhol, front whicli it is precipitaled bycold water; it is piingent, but not very acid to the t te; in iis usual state iis Meli is fragrant, especialty when it istiea od; but this odour has been supposed to arise Dom a minute portion of the oil of the balsam adhering to it; as byxepeated combinations With an ut haline base, and precipitation by an acid, it is obtained ut longili inodoro . It is noteastly decomposed by the action of the more potversul acilis. Decomposed by heat, it afforct a larger quantity of empy- .reumatio Oil than any other vegetable acid, wheuce hydrogenis supposed to predominate in iis composition. AcΕΤ1c Ac 1 D. This acid is more exclusively the productos fermentation ; it erisis likeu i se, h0wexer, ready sorinedin the sap of the vine, anti, combined with arualis and earilis, in illo sup of planis. In iis pii e and concentraled Stare, iuwhicli state it can be procliued only by artificiat proceSSes it is a very po versul acid, hioly ptuageni and Dagrant, volatile and instan able. It is distinguished by the peculiat
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action it exeris on sonae of the other proximate principies of planis,-eSSenties Oil, vestia, gum-restu, camplior, gluten, and caouishouc, whioli it dissolves Without decomposing. Helice, even in iis dilutod state, under the forni of distilled vinegua it is sumetimos used as a solvent in pharmaceutic proceSSes ;though it is soldom that it can he empl0yed to advantage, as itis liable to modify the powers of the substances it disSolves. ΡRUssIc ID. The substance to whicli this name isgiven, is formed froni sonae varieties Os animal mulier by artificiat processes. It had osten been remarked, that iis odouris similar to that of the peach blossona, and that the sameodour is perceptibie in the distilled water of the chero tu res, and of the blater almond. This led to experiments outheSe ; whenco the fact, rather singular, has been discovered, that ali of them contain this acid. The faut, not. lessimportant, has been est lished, that the narcotic property possessed by these distillied waters, dependa on the prussio
acid. In iis insulated state, this substance is volatile, sothat it escapes even DOm iis Wale Solution under exposum to the air. It has no s2nsibie foui ness, and does not reddeneven the more delicate vegetable colours. The character of
Severat of the vegetable acids, particularly the citi ic, malic, and tartario, exist in the Same veget te, and in propo tions Varying accor ling to the stage of vegetation, Wheiace it. is probable that they aro mutuatly convertibie. They arofeld0m pure, but generalty in combination avitii saccharine, mucilaginous, and extrActive matter. Cumbined Willi aika-
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sine and earthy bases, they forin What have been numed thuessenties salts of planis. The last of the proper proximate principies of vegetabies is LIGNIN, OP wood; the substance Whicli, composing ille vesseis of the plant, is the basis through whicli the other principies are diffused, or toe whicli they are attached, and Malch is the basis therelare of ali the paris of vegetabies, with the exception of their secreted juices. It is, whensi ced froin the principies diffused through it, insipid, inert, and insolubie, ii te in a humid state to Slow spontaneou ἀdecompoSition, inflammabie, and is decomposed by heat, leavilag a large residuum os Charcoal, whicli indicatos carbonto be iis predominant ingredient, a 'heiaco proh ly ariSes iis solidity and comparative chemicat inactivit Eeing inso-Ιulbie in matur, or in athohol, it fornas the greater part of thexesiduum, V en the active matter of vegetable substances has been abstracted by maceratiou in these solvents.
Eesides the principies whicli can thus bE obtained in adisthici Dum Dum vegetabies by analysis, there are Othersos a more Subile nature, the existerice of hicli has beeu
supposed to he established by sume facis, though they are AcarceIy capable of bemg exhibited in an insulated state; such are the Aroma or Spiritus Rector os planis, the Acrid Principie, ille Bitter Principie, and the Narcotic Principie. The A ROMA is the principio in v hicli ille odour os planis has been supposed to reside. This quality is generalty Dimitin the essentiat Oil; but there me Some vegetabies, havmga strong odour, whicli yield litile or no essentiat oti, such asthe jessamine, the violet, or the rose ; or, is this od bo procured froni them in sinali quantity, it has not that strengilios odo whicli, considering their fragrance, and the small-ness of iis quantity, might be expected Dona them. I heyexhale this odo , ho vover, Wheu exposed to the aii' ; it is
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ut tengili dissipated; or it is communicated tO Water by dis tillation at a very gentio heat. Helice it has been concluded, ibat a principie moro subile thau the essenties Oil erisis iuri hicli the odorre resides, and that it is even this principiewhicli commmaicates odour to the Od. These facis, however, are inconclusive. The properiy si 'odour may belong to any of the p ximate principies of Veget les, and does belong to principies of very differentiands; it exius in ollier hodies in Which we cannot sup-
ΡοSe the existence of any common principie ; nor is there any reuSOn to RSsume the existence of such a princise iuplanta : and ali the facts considered as favourable to the opinion, are acCounted for on the supposition that essentiat ollis the more common principie of odour, and is c able of be-ing volatiliaed in sinali quantity at a low temperature, and of thus heing diffused through the atmosphore, OP Communi
The existence of an Acrid Principis has been inferredhom an acrimony residing in sonte planis, whicli they loso ondi ing, While their Other activo powers remalia; and Domitiis acrimony being in sume cases transferred to water Or auhohol by distillation. It is not very certain, however, Uthis qualio is not in such cases connected with some of ilio 0Wn proximate principies ; nor has this acrid principie, is it do orist, been obta ed so a. to submit it to chemicat e
BITTER PRINcipLE. A principio of bitteraess has been Eupp0Sed to exist in sonae vegetabies. It is ObVious, hoWever, that this quality may helong to any of the known proximate principies ; and the charactors which have been assim ed to this principie as it cxists in sonio of the purest vegetablebis ters, particularly in genti an or quassia, Sucii aS equid Solu
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A N arcotic Principio has been supposed to exist, Bom tho narcotic power of Some vegetabies being impiared by age, thout any apparent Ioss of mattex, and stram iis heing rendered inert by decoction, though no volatile matter is collacted possessed of the quality. But suchi facts are rathersavour Ie to the conclusion, that the loss of pοwer is owingio chemicat changes in one or Other of the known principies, proba the extraci, in Whicli the narcotic quality may besupposed to reside. In Submitting optum to analysis, it has hceu talamed, that a crystalline matter is obta ined, whicli proves narcotic, and has been supposed to bo the principieon whicli that quality posSessed by the optum dependg. Butit does not, admitting iis existence, appear to he possessed of the narcotic property in that hio degree we should cxpect, ivere it the principie on whicli that proper is dependent, nor is there any proos that it exista in any oster
The existorico of ad these principIes, thexesore, is problemvices ; and the qualities assigned to them man withmore probabilis y, be referred to modifications of composition in the known vegetabie principies, Wllicli axe probably too subile to bo doleonined by chemical analysis. ΑΙ Rouo L, and the ETHERs formed Boni Alkohol by thoaction Os acids, cannot strictb be regarded as vegetable p ducis ; yet they havo a relation to these, as their chemicat Constitution is similar, and they cinnot be sormed but bychanges producod in vegetable matter. AS important, medicinal, and pharmaceutiu uenis, ilio axe entilled to noticu
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Argoi30 L is formed by the process of fermentation hom Saccliarine mauer, or froni fecula, the lalter bemg previsustysubjected, partialty at least, to the operation os matting, bywhicli it is converted into the former. The semented liquor belligesistilled, affords aikohol diluted with water, and with Sume impregnation os od0ur froni the fermenred S Stance. Fr0m this pure at hes is procured by repeMed distillation, the abstraction of the water hom it heing aided by the actionos potasti, or sub-carbonate os potaSh. Alkohol is a colourlegs transparent fluid, having a specific avitra accordi g to iis state os concentration, froni 0.S. oto 0. 800 ; it is fragrant and pungent, and in iis action on theliving system exerta a high degree of sthmilant anil narcotic pora er; it is volatile and inflammable assording, duringils combustion, water aud carbonic acid, the quantity of Water excelding even the weight of the eskohol. It contaiys, the fore, much hydrogen in iis composition, With whicli carbon is combined, and perhaps also a portion of oxygen . . It combines With water in every proportion, and , in conse que e of the urintly belrueen these fluids, they mutuatly precipitate substances V hich either has dissolved, that aro insolubio in ille other. It is decomposed by the acid8, an larding, as the principat produci, the disserent ethers. As a
ETAER. The nainu Ether is sven to a peculiar producti tu ined by the action os the more poworsul acids on aikohol, tho produci dissering in iis properties according to the acidems0yed in iis formation, but in general bcing extremelylight, volatile, and innamma te. Sulphuric ether, servied by
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0T THE GENERAL PRINCIPLEstho action os sulphuric acid on aikohol, lias a specific gravityΠ0t greater, when it is pure, thali 0. 710 ; it is so volatile asto evaporate rapi ij at the common temperature of the atmosphore ; in burning it assords water and carbonic acid : iis odour is fragrant anil penetrating; iis taste pungent; it issolubio in water only in limited proportion, about one paxι
in ten. It exeris on the vegetabie principies the fame solvent action nearly as aikohol, excepi on extraci, whicli it has beensaid to precipitate,-- effeci, however, I have oot been ableto obtain froni it. Nitrio ether is equassy light and evenniore volatile ; it is inflammable; it is solubie in ivator in limited quantity, but combines With aikohol in every propo tion : iis odour is strong and peuetrating. Muriatio ether is more volatile than either ; it exigis in the state os gas, under the atmospheric pressure, at 609 ; at 50 it hecomes liquid, and iis specific gravity is not less thau 0.874; it is transpa-
derately light, volatile, and inflammabie, sol le in Water in limited quantity, and has an Odour etheriat, but approachingalso to that of vinegaria Ali these ethors appear to disserfroni aikohol, principalty in haming a larger proportion of hydrogon in their composition, to whicli probabb their greater levity and volatilily are to be ascribed; and they generassycontain a portion of tho acid by the action of whicli theyliave been formed, whicli, in Some of them at least, reppears essenties to their chemicat constitution. ΠΑviso potnicit out the distinguishing proportios, and tho generat pharmaccutic relations of the Proximate Principies of Vegetabies, it may be proposed as a questi in potet aut tu relati in to the olfect of the preseiat ouillae, DO ili c
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DF PIIARMACEUTIC CHEMISTRY.pi incipies usualty exist in the vegetable in a stille of chomicas combination, whetice sonte modisi cntion os their powers may result, or are they more generalty mechanicatly mixed Z The lalter appears to be generalty the case. Ihese prit1-cipies cata osten be observed existing repart ironi ea ch other, and even placed in separate vesicles ; they can in many caSeSbe separated by mechanical means ; and eVen where they aro more intimately inhved, that change of propertios does uosi ake place, which we must have expected were they Chemi . Calb united, tho virtuos of each principio being discorniblo in the entire mixtim e, weahened, but not Changed. It Seemsto soll0w, there re, that the virtves os vegetable substanc do not depend ou chemicat combinations of their proximate principies, but rather on the peculiar ultimate compositionos one or other of these principies. Heiace also it is evident, stat in separating the proximate principies of any Vegetabie, me cannot expeCt to alter Or improve iis viriues, farther than in concentrating them by a separation f in What is inert, orin separating principies Whicli are possessed os dimearent oreven opposite pOweYS.. The attainment even os these ends,however, is, in innumerable casus, of importance in their exhibition as medicines. From this enumeration Os the Proximate Principies of Veget les, maybe explained the rationale of those pharma-ecutio processes to wllicli planis are usualty subjected. Veget te mattor heing liablo to dccomposition when in ahumid state, froin the re action of iis elemenis, and thei Pentering into ne v combinations, I xsiccation is an operatiou
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OF ΤHE GENERAL PRINCIPLEsInspissation is an operation persea med on ille expressed juices of planis, with tho fame vie , the dissipating tho vatery portion of the juice, and thus coininimicali g to it athick or solid consistence, rendering it less liable to those spontaneous chemicat Ganges whicli it would otherwise --dergo. It is per i med by the application of a gentio heat. By infusion os vegetable matter iv water, the fluid is im- pregna ted with the gum, Sugar, eXtraci, tanta , Saline Substances, part of thel essentiat oss, and part also of the resinous principio. The aroma of the plant is generalb frattaken up : by lovger infusion the water is Ioaded with the
colouring, astringent, and gummy paris : theSe are alSo most abundantly dissolved when the temperature is hio. Helice an infusion differs according as the water has stood longer orshorter On the materiais, and a cording as it has been promoted or not by heat. An infusion made in the coid is in generat more gratefies, while one made with heat, or by Leeping the fluid long upon the materiais, is more Strongly im- pregna ted with active matteria By Decoction or botling, the solvent potver of the wateris stili farther increa sed ; and hcnce the liquor always appea darker coloured, and it is more loa ted ii illi thoso principies of the vegetable whicli it On hold dissolvod. Those, howovcr, Whicli are volatile, particula ly tho essenties Oil, arecntia ely dissipated ; and thores ore it is an improper processsor vegetabies, the virtuos of whicli depend, Wholly or pat-ties ly, ou these principies. Exen some of the sXed principies of vegetabies ure iis ed by long decoction. The extractivo