168 C H E M 
paration at the fnrfaces of plants, even by the power of 
vegetation : thus the'fapf manna, gum, refin, &c. ipon- 
taneoufly flow; though art is often obliged to feparate 
from each other feveral of thefe materials united and 
confounded together. The means it employs for this 
purpofe are ufually fimple and eafily practifecl; fuch as 
reft, filtration, expreffion, ablution, and diftillation with 
a gentle heat, which produce no alteration in the jub¬ 
ilances fubjefted to thefe procefl.es. 
Among the materials of vegetable bodies obtainable by 
fimple means, which, change not their nature, may be 
reckoned the following lubitances, either fluid, or folids 
i. The extra&ive matter, or extract. 2. Mucus, or mu¬ 
cilage. 3. Sugar. 4. EiFentiai lalts. 5. Fixed oil. 6. 
Volatile oil. 7. Aroma. 8. Camphor. 9. Refin. 10. 
Baliam. n. Gum-refin. 12. Fecula. 13. Gluten. 14. 
Colouring matter. 15. Elaftic gum, 16. The ligneous 
part. Betide thefe lixteen principles, a fubftance analo¬ 
gous to animal albumen has been discovered in the ana- 
ly (Is of vegetables; and Jit is probable, that fpme other 
unknown vegetable principles, exift, as the matter pro¬ 
per for tanning hides, or tannin, Sec. 
It is necelliiry here to be fully aware, that, on reducing 
all the faffs of vegetable analyfis to general terms, or 
leading refults, nothing more has been found in any of 
the plants hitherto examined, than the eighteen jub¬ 
ilances above mentioned; fo that we may ailirin, that 
they actually compofe the texture of ail known vegeta¬ 
bles, and that a very accurate analyfis is made of a vege¬ 
table,. when we feparate thefe from it. Yet it is not to be 
underftood, that all thefe eighteen immediate materials are 
to be found in the different parts of vegetables, or even in 
each vegetable taken all together. There are plants, all 
the parts of which do riot furnilh fo many as five or fix of 
thefe materials : others contain eight or ten; fome afford 
them all. But fuppofirig we could mingle arid biend toge¬ 
ther,even chemically, all the plants which have ever occu¬ 
pied the attention of the chemi ft, this mixture, this combi¬ 
nation, confufed in appearance, would exhibit only the fix- 
teen or eighteen above mentioned fubftances, as the re¬ 
fults of the moft accurate and refined analyfis; whence 
we are juftified in faying, that vegetables are formed of 
thefe immediate materials. Each of the materials above 
announced has peculiar diftinguifhing properties, among 
which thofe that can mark its characters, and render it 
eafily difcernable from the reft, fnould be feiefted. It is 
by no means impoffible to treat this fubjeft after the 
manner of botanilts, and to have but one dharafleriftic 
or fpecific phrafe for each of thefe materials: and though 
this method has never yet been executed in chemiltry, 
Fourcroy prefents a lketch of it in the following manner: 
Characters of the immediate Materials of Vegetables. 
Extractive matter, or extract: Dry; brown; 
a little deliquescent; foluble in water; obtained from 
the juices of vegetables by iiifpiflation, or from decoc¬ 
tions or infufioris of them by evaporation; affording by 
diftillation an acid, a little ammoniac, and fome oil; ab- 
fiorbing oxygen from the atmofphere, and by this abforp- 
tion becoming gradually infoluble; erroneoufly confi- 
dered as a native foa.p; compofed of carbon, hydrogen, 
• azot, and oxygen, and always tending to abforb more of 
the laffc than it contains in its primitive ftate. 
Mucus, or mucilage: An agglutinative, vifeous, in- 
fipid, lubftance; affording-much pyromucous acid on 
diltillation ; foluble in both warm and cold water; ab- 
lorbing no oxygen from the atmofphere; drying and be¬ 
coming brittle in the form of gum; exifting in roots, 
young (talks, and leaves; ifluing from the bark of trees 
by expreffion; gluing their fibres together. 
Sugar : Sapid and agreeable to the tafte; cryftalliza- 
ble, foluble, and fermentable; in moft circumftances re- 
Jfembling mucilage, but differing from it in the property 
of fermenting and forming alcohol. Both mucilage and 
fugar are compounds of carbon, hydrogen, and oxygen; 
I S T R Y. 
differing from extraft, ift, By poffeffing a fmaller pro¬ 
portion of hydrogen, on which account they do not ab¬ 
forb, like extraft, the oxygen of the atmOljphere; 2dly,- 
By the abfence of azot, whence they afford no ammoniac 
on diftillation. 
Essential salt: Comprehending the vegetable acids, 
formed in general of hydrogen and carbon more oxy¬ 
genated than in the three preceding principles: accord¬ 
ingly thefe are convertible into acids by the addition of’ 
oxygen. Vegetable acids, however numerous they may¬ 
be, appear to differ only in the proportion of their three 
principles : they are all decompofable by fire, capable of 
being converted into each other, and, cn an ultimate 
analyfis, are reducible to water and carbonic acid by the 
addition of oxygen. 
Fixed oil: Formerly called grofs or exorefled'oil; 
thick, fweet, inodorous; burning when volatilized; form¬ 
ing joap with cauftic alkalis ; mixed with a mucilage 
named the fweet principle of oils by Scheele; infpifiating 
and becoming concrete by the contact of air and abJorp- 
tion of oxygen; experiencing the fame effedts by the ac¬ 
tion of acids and metallic oxyds; compofed of carbon, 
hydrogen, and a little oxygen. It differs from the pre¬ 
ceding compounds in containing a larger proportion of 
hydrogen; whence arife its combuftibility, and its pro¬ 
perty of being converted into water and carbonic acid, 
when it burns with a fufficient quantity of air, as it does 
in the hollow wicks furrounded on all fides with air, 
which conftitute Argand’s lamp. 
Volatile oil: Heretofore named effential oil, or 
effence: highly acrid, highly odoriferous; entirely re¬ 
ducible to vapour at a heat of 184°; combining difficult¬ 
ly with alkalis; capable of being fet on fire by acids; in- 
ipiflating to a refin by the aftion of oxygen; burning 
more rapidly, and affording more water, than fixed oil, 
and admitting more fpeedily the precipitation of its 
charcoal, which forms lamp-black. 
Aroma, formerly called fpiritus reClor: Avery vola¬ 
tile principle, reducible to vapour by the.ordinary heat 
of the air, and forming an atmofphere round plants; 
paffing over with water in diftillation in balneo Maria-, 
lometimes of an inflammable nature, at others displaying 
faline properties, uniting with alcohol, fixed oils, vinegar. 
Sec. forming by thefe combinations what are called in 
pharmacy diftilled waters; contributing by its prefence 
to the quantity of volatile oil diftilled from plants, and 
bearing fo great analogy to it, that they have been con¬ 
founded together. The nature of aroma is not accu¬ 
rately known; fome begin to fulpeft, that it is not a dif- 
tindt body, a jingle principle dijengaged from vegetable 
matters, but theie matters themfelves in fubftance redu¬ 
ced to a ftate of vapour. 
Camphor: A matter now reedgni/ed in a number of 
vegetables, and claiming to be reckoned among their im¬ 
mediate principles; of a concrete and cryftalline form; 
very volatile; burning with the emifiion of fmoke; joiu- 
ble in a large quantity of water, in alcohol, and in ether; 
exifting in feveral volatile oils; contained pure in the 
trunk and leaves of the jpecies of laurel which furniflies 
it; too littie known yet with regard to its intimate na¬ 
ture; yielding a peculiar acid by means of the nitric. 
Resin: AToft or dry fubftance; little odorous; com- 
bultible; foluble in alcohol, but not in water; uniting 
difficultly with alkalis; little alterable by acids; origi¬ 
nating from infpiflated volatile oil, and appearing to dif¬ 
fer from it only by a larger portion of oxygen. 
Balsam-. Refin united with benzoic acid; more odo¬ 
riferous than pure refin} affording its acid in a concrete 
ftate by the agency of fire and water; yielding it to al¬ 
kalis or earths; and approaching to relin after having 
loft its acids. 
Gum-resin: A concrete juice; partly foluble in wa¬ 
ter, and forming with it a kind of emuliion, as it does 
with vinegar, which has been fuppofed its univerlal men- 
ftrunm, but ftil! more foluble- in alcohol: net cXudin 
natural) 
