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Τheir analysis is also Sometimes executed by the agoncyos the nitrio acid, whicli communicates to iliem oXygen, and by the produci ascertaius the nature of thela acidis able baso. This mode of analysis by oxygenation has lately been rendered more exact in the . execution by a variation introducet
nation of the oxygen of the salt with the elements of the vegetabio substance heing collected. His experiments estu-bi isti tho important generat resulis,-that in One class of vegetable producis, iliose whicli are of the nature of gum orsecuta, tho o gen and l drogeii they contain axe in that proportion to each other Whicli forins water, iliore belligadded to this a certain quantity of carbon ;-that in anotherclass, those whicli are acid, the oxygen is to the hydrogeuin a Iarger proportion than that whicli forins water ; and that in a third class, composed of those whicli are Oily orinflammabie, the hydrogen is in larger proportion. The sol ἰ0wing table presenis these resulis, and the proportions of the elements of some of the most important vegetable proxima te principies, as assigned by this method.
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iupp0sing itie Oxygen anti hydrogeia in the state os water in the substance. 8ubasances analysed.
e ultimato analysis of the veget te substances betonse ing to the Materia Medica is sellioni os utility, since we can scarceb ever discover any relation belween tho composition . and the medicinal powers of the Substance analys d. These, in common with ali iis propertios, no doubi dopend on that composition ; but our modes of analysis are stili too limitedand imperfect to admih of ouae tracing the Connection belweeuthem. The application of chemisti , there re, to the vegetable substances belonging to the Materia Medica, is in agresti mensure confined to the di8Crimination os thoir pro i mate principies. The Proximate Principies os vegetableS Rre numerouS,
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u illi in every vegetabie, OF in every period of vegetation :sonae exist only in certain planis, Mid that onb in thoir stato of vigour anil malimqty : at ollier times they are to bo fomid. only besere they have arrived ut that period ; sonae are de posited in particular organs, others are diffused through thes
vliole substance of the vegetabie, and mixed in a manu Pinore or less natimate vitii ali iis partS : and Some a re neari peculiis to certain vegetableS, While Others are Common to ulmost every plant. Those only xequire to be potnted out
in this sketch, wluch are particularly connected with medita cinal properti . These principies are the producis os vegetation Dom a common juice OP Sap, Whicli circulates freely through exae part of the vegetable SyStem, being supplied by absorptious poni the soli, and perhaps froin the atmosphere. It varies in iis qualities, particularly aCCording to the season, and the . progress of the plant to anat ity ; frequently tuo it has an intermixture of the proper juices: it always contains thousual elemonis of Vegetable matter, With generassy saline sub
otioni changes it suffers froin the action os the vesscis of the
plant, aidod by the action of the uir und of licti, iis ole-menis pass into various States of Combinations, whenco the peculiar producis of vegetation ure fomed. 1 ho si si transition of this sup appears to he litto MUCI I AGE, OP CUM, One of the proximate principies contain diti great est abundanoe in g tables. Cum is the nam o Hucuit Olatainod hi a coire a Cte uto I uini ge i S the nauae given to it whon it is expresso i in aiquac state, Or extracted by maceration in Wator. Γ trie nilix Se titero oxist sume distet ences in their rotation to ri
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This principio is found in ali yo g planis, tu greater orless quantity ; and is osten so abundant in the plant, us to bedischarged by spoutaneous exudation. Ιt abounds also in their roois, stallas, and leaves, alia especialty in their Seeds. It is an uiodorous, insipid, and glutinous substance, Solubleiu Water, in every proportion, andi forining with it a thicla viscid solution, which by evaporation a Orti a tenaciouSmass, that when desed is britilei and again sol te. It is in-Solubie tu aikohol, ether, or Oil, and is precipitaled stom iis solution in wator by the addition of aikohol. It does nota sorb oxygen sim the alimosphere; though iis solution b comes Sensibb acid by ke ing, o ving to parties spontaneous decomposition, and the combination os part of the principies of the gum, So as to form acetic acid. Exposed to heri it laneither fusible nor volatile. At a temperature superior to212, but inferior to that os ignition, it is decomposed ; iis
principies entering into new combinations : the producis arean acid liquor, consisting principalty of acetio acid, carbonica id and carburetted hydrogen gases, i th a litile ammonia, and a residuum os char at containing lime, one omice
of gum, assording 6 graius os time. This lime is uiso detected by adding sulphuric acid to a solution of gum. Fromthese producis of the analysis, it is evident that the uutimate principies of gum are, oxygen, hydrogeia, and ca bon, With Smallex proportions os nitrogen and lime. Cumis not capsile of passing into the vinous sermentation, hichappears to be o ving to the portion os limo existing in it, uslime has the effect of preventing even fugar DOm Suffering
Gum is not inflammable; for although, when beated, in contact with atmospheric ulla, it combines With oxygeu, it
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OF PII ARMA EUTIC CHEMISTRY. 43emiis no sanie. Tlio principia producis of this combination
Iis existerice in vegetabies is detected by bolimg gently the
egetable substance With water; the water dissolves thegum, and is iniicli of iliat principio be present, the Solutionis glutinous. It may be allowed to rem in illi the impurities bave subsidod ; is it then he evaporated to the consistence ortliin syrup, the addition of three paris of aikohol will separate the ivliole of the gum in fialaos. Pure gum is not an activo substance, considered with re spect to iis effecis on the living system. In medicine it isonly used for iis lubricating cs uality ; and so litile activitydoes it exert, that it has osten been tinen for a considerable time aes an article of Dod. Frona iis chemicat properties, it is of rather more importance. AS a component part Osi eget te matter, it venders the other paris more solubie in vatery liquors, and may thus savour their action On the sto
mach. In Pharmacy it is used as a medium to combino balsams, restias and oiis With Watur. Is a sinuli quantity os ny of these substances be trituraled with a litile gum opinuci lage, on the addition of Water they rem alia suspin dedin it, forming a white mill y-like mixture, retaining ali ille properties of the balsam or Oil. Though pure gum is thus inuctive, yet the virtuos of many vegetabies depend on a
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plant somelimes adhere tu it, Doni whicli it receives colour, Smeli, and taste. Starch is the secula of wheat, and is themost abundant part of that gratia. Fecula is insolubie in alkohol. Tho action of the acidson it is somewhat analogous to that they exert 0n gum, diS- Solving it when they are u eati or diluted, but decompusingit When they are more concentraled. The arualis also dissolve it. Exposed to heat, it is chareed, and suffers decomposition, assor ling producis whicli indicate carbon, hydrogenand oXygen to be iis constituent principies. A properiyeminently Characteristic of it, and probably depending oniis composition, is that of heing convertibie into Saccharine matter, and theiace ultimat ely passing into the vinous fermentation,-a propero not belonging to guin or any other principie. This conversion talaes place in germination, andis accompanted with an absorption of Oxygen, and formatiouos carbonic acid. Fecula is a substance hi ly nutritivo, and is usualty cout ined in thoso planis V hicli serve as laud. It is somelimes employed in iis pure state in medicine, on account of iis nutriti Vc quali ty, and froni bcing easy os digestion ; Sags and Talop nro SubStauces of this Lind.
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ia, and is obtamcd in ille process in Whicli the secula is separate l. It then appears as a viscolis, elastic, and sibi ous- like substance, whicli, Dum iis close resemblance to ille animal produci namcd Gluten, has been denominated I cae- tablo Gluton. It is obtained froni the noue os wheat iugreatest abundance: the fioue is made luto a paste with vater, Which boing compressed by the hand, vhile a stream of water falis upon it, the secula is ea ted ost ita the state orp0wder : the mucilaginous and saccharine paris of the grainare dissolved by the water ; and there rema ins a tenacious ductile mass, forming the gluten ; it haS Scarcely any inste, is os a mensti colour, and when dried is semi-transparent, resembling sue in iis appearance : it is insolubie in Water,
and is dissolved in very smali quaesity by esk0hol: by the
action os nitrous acid, it is converted into OXHic acid, giving out, at the Same time, nitrogen gas: decomposed by heat, it inords a large quantity of ammonia, and it is subjeci like animal matter to putrefaction. It Contains a largerproportion os nitrogen than any other veget te productdoes, and it is supposed to render those vegetabies in whichit is present hi j nutritive. other principie whicli has been supposed to exist in vegetabies, is that whicli has been named Albumen, fi om iis res blance to the animal principie of that naine. It is solubie in cold water, iis solution heing coandated by hcat: itis coagulated also by aikohol, but is dissoluod by the est alis: like gluten, it is liablo to putrefaction, and fui nishes a large quantity of ammonia by distillation. This principio is suundin hemioch, Scurvy grass, cresses, and Severat Other planis, and is obtainud froin the fresti expressed juice of illo leaves When they are heated noarly to tho boiling p0int; the albi min0uS matter coagulating, and separating in the sorin ossa s. A similar separation tul es placu. On the additi0n os
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OP THE GENERAL PRINCIPLEsaphisit of wine. It is containuit also in the scolis os other planis, particularly in the disserent nutritivo gratus ; in thesuina os wheat, for instance, it is mund dissoluod in the water V hicli is empl0yed in separating the secula Doui the uton. This principie has, liori overi been regarded, and perhaps just b, as a varicty of gluten ; it differs titile Domit in chemicat properties ; and the peculiar physical qualities supposed to bo distinctive os gluten are obviousty derived frum the process by Whicli it is obtamed.
SAccHARINE MAΤΤER. Tliis exisis in many vegetable Substances, especialty in thela fruits and rosis, but osten intimately united with their mucilaginous and exta active mat-ier. When Deed Doni these, iis tu te is meet, Without any peculiar flavovi'; it is solubie in V ater id in alkohol; - is capMale os crystalliging ; its watery solution enlers sirstinio ille vinous, and then tuto the acetous fermentation. Bythe action os nitrio acid, it is convertod into Oxalio nold;
by decomposition by licat, it assovds a large quantity of em-
pyreumatio acetic acid, a Sinali quantity of empyreumaticoit, carbonic acid and carburet ted hydrogeia gases, the residuum heing charcoal. It consisis, theresere, of carbon, bydrogeia and oxygen ; and Dum the large quantity or acidwhicli iis analysis yields, it appears to contain more OXygeathan any other vegetable substance that is not acid. Sugar appears to be osten sormed froni the secula of the veget te in Q hicli it oxisis. It contains neaarly the sam principies as secula does, and the operation os matting thmu sconsiderable ligilt on iis formation ; in this process, the se cula of grain is converted into saccharine matter, oxygen is absorbed, and carbonic acid formed ; and this abstractionos carbon, is it constitutes ille whole chango, Of course proves that the fugar, whicli is the produci os the operation, has an increased proportion of hydrogen and oxygen.
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In other ea es, as in the maturation Os fruits, Sugar appea irato be formed from the acid juice of the fruit, and this inprobably effected by an abstraction of Oxygen . Saccharine matter has litile activity, though there are sonae varieties orit, in Whicli sonie weali medicinal powera reside . QOIL is a common proxima te principie of vegetable matter; it is of two tanti, expressed is sat Oil, and distilled, volatile, or e senties est. These have the common qualities ofunctuosi ty and inflammabili ; but they also possess peculiarproperties, vllicli they are distinguished as species. Itio Expressed, set, or fixed Ods, are thicli and unctuous, insipid and inodomus; they congeat ora exposui e to Colit, ureli ter than water, and insolubie in that liquid; they are Iikewise insolubie, excepi in very minute quantity, 'in' aikohol, and they combine with the aes sis, forming Soap. Tli are not volatiliZed at the temperature of 2I2ς e some requireto be mised to 600ψ to mino them holi, and the condensed odis changed in iis properties. At a temperature Somea diathigher, they axe decomposed tu close vesseis, and hurn whenthe atmospheric ab is admittest. They also flowly absorb oxygen at a low temperature ; a Sinali quantity of an acid is formed, Whieli renders them rancid ; by longer exposure tothe ala, illo are inspissated, and even hecome at lennii concrete. Those otis in particular Which have been expressedwith the aid of heat, and wllicli are named drying olis, sufferthis last change, and are ultiniateb convertod into a resinous
Expressed olis consist chiosy of carbon and bydrogeir, asis established by the producis os thoir decomposition byheat, Whicli are chiesy carbitret ted hydrogen aud carbonicaci d. The producis of thela combustion are Water and cur-houic acid.
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or vegetabies, and ouj at the period of their maturity. They are extracted by expression, or by decoction ivithwater; they axe frequently impregnated with part of the
tractive, mucilaginous or resin0us particles, whicli theseed or fruit contains; Dom P hicli they derive colour, and in many Cases a pecultur iaste and odour, and even perhaps Certaui medicinal powers. In generat, however, they have titile activity as medicines. They are mild and emollient, and are used principalty for these virtves They are rendered miscibio ivith wator by the medium os gum or Sugar, or by the addition os a sinali quantity of any of the aikalis. Volatile or Essentiat olis have characteristic properties disserent froin those of expressed olis. They are volatile ata low temperature, and are enthely and quicEly converted into vapour at thoe heat of boiling ater, without bemg M-i composed ; they are. solubie in a Sinali proportion in mater,nnd honce the imprognation whicli Mater receives Rom many veget les by distillation. In alii obol, they are completelysolubie ; but they. do not combine with the athesis ivitii faci- Iity ; th are in generat odoriferous, pungent, and even n-ci id ; they are more bighly inflammabio than the Ged olis, and by eXpoSure to the ut mosphere they Slowly absorb oxygen, are thichened and coloured, lose much of their smolland pungency, and stre at tengili converted into substances ofa resinous nature. This change is partly owing to the volat ligation of the od, but principutly to the oxygen absorbed combining with a portion of their hydrogeii. These otis, froni theu analysis is heat, or by combustion, appear to consist principialy of carbon and hydrogeu. Theydissed froni tho fixod olis in containing a larger proportion os hydrogeia; hunce they are more volatile, and more instam-mabie, and by combustion assoxd a larger quantity os aquosus