22 MINUTES OF 



On the component Principles of Vegetables. 



lime frolTi the sulphuric acid. The principal character which may serve to estab- 

 lish a line of distinction between the vegetable acids and others are-l. Their 

 vplatility; for there are none which do not rise with a moderate heat. 2» Their 

 property of leaving a coaly residue after combustion, and of emitting an em- 

 pyreumatic smell in burning. 3. The nature of their acidifiable base, which is 

 in general oily. 



The acids produced by vegetable secretion have of late been much subject- 

 ed to chemical inquiry, and have been found to be so numerous, that they have 

 been named from the vegetables, or parts of vegetables, from which they have 

 been extracted; as the citric, malic, ojcalic, tartaric, gallic, and benzoic acids. 

 The citric acid is obtained from the fruit of the citrus medica and aurantium, 

 limonia acidissima, berberis vulgaris, punica granatum, rubus idsus, ribes rubra 

 and grossularia, pinus cerasus, and vaccinum myrtillus. The malic resides in 

 the fruit of the pyrus mains and cydonia, fragaria vesca, rubus chamsemorus, 

 vaccinium myrtillus, and sambucus nigra. The oxalic, in the leaves of the oxalis 

 acetocella and corniculata, geranium robertianum andacetosum; in the root of 

 the rliEeum rhabarbarum, bryoniaalba, andhelleborusniger; the boletus suberosus 

 also exudes an acidulous humour, which, inspissated by the rays of the sun, goes 

 into very pure crystallized oxalic acid. The tartaric is found in the fruit of 

 the tamarindus gallica, and in the root of the rumex acetosa, and others. The 

 gallic acid is detected in all astringent plants, combined with the gummous 

 principle. 



Lastly, the benzoic acid is obtained from gum benzoe and balsam of Peru, 

 and lies concealed in the balsam of tolu and in storax. 



Many unripe fruits contain an austere acid, which is gradually converted 

 into sugar by vegetable or chemical processes for the nutriment of their seeds, 

 in other plants it exists in the foot-stalks of the leaves, as in rheum, rhubarb ; 

 or in the leaves themselves, as in oxales, or sorreU 



