ion 



CHEMISTRY. 



Nature. 



->' may conclude that it is universally diffused. The quantity 

 of it it very small, and therefore determined with difficulty. 

 At first it was conceived to amount to ,!jth of the at- 

 mosphere, but it is certainly much less. Humboldt 

 found it to vary from 0.00.') to 0.01 ; but his method 

 does not seem susceptible of precision. Dalton made it 

 TjWffth of the air. Perhaps we shall not err far if we 

 _ reckon it at a medium at i^Vrth of the air. If we con- 



sider the numerous sources of this gas from the combuj- 

 tion of wood and coal and the breathing of animals, it 

 must appear surprising that its bulk does not sensibly 

 increase. This can only be accounted for by supposing, 

 that nature has provided some means to decompose it as 

 "fast as it is formed. 



For an account of the changes which take place in the 

 atmosphere, sec METEOUOU 



BOOK IT. Of Waters. See the article WATERS. 

 BOOK III. Of Minerals. See the articles GEOGNOSY, 

 MINERALOGY, ORYCTOGNO.SY. 



BOOK IV. 

 OF VEGETABLES. 



Vegetable!. VEGETABLES are exceedingly numerous, nearly 40,000 

 species having been already described and arranged by 

 botanists. It is the business of the chemist to analyse 

 vegetables, to investigate the substances of which they 

 are composed, the processes by which they are formed, 

 and the changes to which they are subject after they 

 have ceased to vegetate. We shall divide this Book in- 

 to three Chapters. In the first, we shall give an account 

 of the ingredients of plants ; in the second, of the chemi- 

 cal phenomena of vegetation; and in the third, of the fer- 

 mentations to which certain vegetable substances arc 

 liable, after they have ceased to vegetate. 



CHAP. I. 

 Of the Ingredients of Plants. 



Ingredients THE substances hitherto found in the vegetable king- 

 of plants, dom, all of them at least which have been examined 

 . with any degree of accuracy, may be reduced under 

 four heads : I. Substances soluble in water, at least 

 in some state or other, and which, -in general, are so- 

 lid and not remarkably combustible. II. Substances, 

 either fluid, or which melt when heated, and burn like 

 oil. They are all insoluble in water ; but, in general, 

 they dissolve in alcohol. III. Substances nekhcr solu- 

 ble in water, nor alcohol, nor ether, and which have a 

 fibrous or woody texture. IV. Substances which be- 

 long to the mineral kingdom, which occur only in 

 tmall quantity in vegetables, and may therefore be con- 

 sidered as extraneous or foreign. The following Ta- 

 ble exhibits a view of the different vegetable substan- 

 ces hitherto, discovered, arranged under their respective 

 heads. 



Table of 



vegetable 



MMMb 



I. I. Acid*. 



2. Sugar. 



3. Sarcocoll. 



4. Asparagin. 



5. Gum. 



6. Mucus. 



7. Jelly. 



8. Ulmin. 

 P. Inulm. 



10. Starch. 



11. Indigo. 



12. Gluten. 



13. Albumen. 



14. Fibrin. 



15. Bitter principle. 



16. Extractive. 



17. Tannin. 



18. Narcotic principle. 



II. Olfnfurm. 



1. Fixed oil. 

 '.'. Wax. 

 :>. Volatile oil. 

 4. Camphor. 

 fi. Bird-lime. 



6. Resins. 



7. Guaiacuoi. 



8. Balsams. 



9. Gum resini. 

 10. Caoutchouc. 



ObemicM 



'ma- 

 lion V I 



Nature. 



1. Cotton. 



III. Fibrous. 

 2. Subcr. 



55. Wood. 



IV. Extraneous. 

 1. Alkalies. 2. Earths. 3. Metalt. 



The properties of these different substances form the 

 subject of the following Sections. 



SECT. I. Of Acids. 



The acids found ready formed in the vegetable king- Acid* 

 dom are the following : found 



ready 



1. Acetic. 4. Citric. 7. Benzoic. formed ia 



2. Oxalic. 5. Malic. 8. Prussic. vegeublcv 



3. Tartaric. 6. Gallic. 9. Phosphoric. 



The sulphuric, nitric, and muriatic acids, are likewise to 

 be found in vegetables combined with alkalies, but only 

 in small quantities. 



1. Acetic acid has been detected in the sap of different 

 trees, in the acid juice of the cicer paricliiium, and in the 

 sambncus nigra. 



2. Oxalic acid in the state of superozalate of potash, 

 exists in the leaves of the oxalis acetosella, ojcalis corni- 

 citlala, and different species of rumex. It exists uncom- 

 biued in the juice of the cicer parietinum. In the state 

 of axalate of lime it is found in rhubarb, and in the roots 

 and barks of a great variety of plants. 



3. Tartaric acid is found in the pulp of the tamarind, 

 in the juice of grapes and mulberries; likewise in the 

 rnmex acetosa, rlius coriaria. ihetnn rfuiponticum, agave 

 americana, triticum repens, li-onlodoii taraxacum. In most 

 of these plants it is in the state of supertartrate of pot- 

 ash. 



4. Citric acid is found intermixed with other acids in 

 the juice of oranges and lemons, and in the berries of vac- 

 cinium oxycoccos, vaccinium vilis iila-a, primus padus, so- 

 latium dulcamara, rosa canina. Mixed with other acids, 

 it is common in many fruits. Citrate of lime is found in 

 the onion. 



5. Malic acid is very common in plants. It was found 

 by Scheele, unmixed with any other acid, in the fruits of 

 the following plants : the apple, berbcris vulguris, prunus 

 domestica, pruttus .-pinosa, sambncus nigra, sorbus aucu- 

 paria. Braconnot has found it in the leaves of most 

 vegetables which he examined. Vauqueliu found it in 

 the state of sii/irnnatatc iff lime -n the following plants; 

 aempcri'ivum feclorum, seilum album, sedum acre, sedum 

 tt-irp/iium, arum maculaium, and different species of 

 crassula and mesrmbrianthemiim. Mixed with citric acid, 

 it constitutes the acid of the t Mowing fruits ; gooseber- 

 ries, currants, bleaberries, cherries, strawberries, cloud- 

 berries, rttspberrifs. Smetimes, as in the tamarind, it 

 is mixed with tarMrir acid. 



6. Gallic acid has been found in the bark of most 



