34ff 
CHEMISTRY. 
united to iron and manganese, in the ore 
called wolfram. The metal is "brittle, hard, 
and very infusible. It is very little known ; 
but is said to have one valuable property, 
viz. that of rendering all vegetable colours 
fixed ; but this does not appear to be certain. 
For the remaining compounds into which 
metals enter, and the order of their affinities, 
&c. see Salts and Metals. 
/ egctable subdances . — Besides the sub- 
stances which we have already described, na- 
ture exhibits another class which are called 
living, or organized beings. These are ani- 
mals and vegetables, which at lirst sight ap- 
pear to be very different from each other, 
yet it is not easy to say precisely, in what the 
difference between them consists. 
Vegetables in general differ from animals, 
in the former being fixed to the earth, and 
not being able to change their situation; 
while the latter are possessed pf loco-motive 
power, which they are obliged to exercise, in 
order to procure food for their sustenance. 
Almost all vegetablesyire composed of three 
principal parts: the bark, or exterior cover- 
ing; the wood or woody fibre, which in trees 
constitutes the principal part ; and the pith, 
which seems to correspond to the marrow of 
animals. The constituent principles of ve- 
getables, are hydrogen, carbon, and oxygen. 
Those are common to all vegetables. Such 
other substances as exist in particular vege- 
tables, are only essential to the composition 
©f those in which they are found, and do not 
belong to vegetables in general. Of these 
elements, hydrogen and o\) gen have a strong 
tendency to unite with caloric, and be con- 
verted into gas, while carbon is a fixed ele- 
ment, having little affinity with caloric. On 
the other hand, oxygen, which in the usual 
temperature, tends almost equally to unite 
with hydrogen or with carbon, has a much 
stronger affinity with carbon, when at the red 
neat, and unites with it, to form carbonic acici. 
Vegetables are analyzed by various means, 
by heat, by acids, by water, and by fermen- 
tation. Some of these processes form pro- 
ducts which did not exist in the living vege- 
tables. Though all vegetables consist of 
hydrogen, carbon, and oxygen, yet these ele- 
ments do not exist in them in a simple and 
uncombined state, but joined together in 
various proportions, forming a variety of com- 
pound substances, which mixed together in an 
organic form, make up the whole vegetable. 
We shall now describe the principal substan- 
ces which are to be met with in vegetables. 
1. Mucilage. Various parts of vegetables , 
imparl to water, if boiled with them, a certain 
viscous consistency : this is called mucilage. 
Some trees suffer their mucilage to transude, 
either spontaneously or by incisions made 
in them. When it has become concrete by 
drying in the air, it is called gum. This sub- 
stance is without taste ; soluble in water, but 
not in oils or alcohol. It is not changed by 
exposure to the air. It appears to consist of 
oxygen, hydrogen, nitrogen, carbon, and lime. 
2. Oils. Oil was formerly supposed to be 
a simple substance ; but Lavoisier proved 
that it is composed of carbon and hydrogen ; 
it also contains a small portion of oxygen. 
Oils are divided into fat or fixed oils, and vo- 
latile or essential oils. Fixed oil is usually ob- 
tained by expression, chiefly from the seeds and 
kernels of plants. It is generally mixed with 
mucilage. It does not combine with water or 
Hlcohuh It. has a great affinity for oxygen, 
which thickens it, and makes it pass into the 
concrete state. Some fixed oils, as linseed 
and walnut-oil, dry of themselves, or become 
solid, in the air ; but this property is much 
increased hv boiling, and adding oxyd of lead, 
which constitutes drying oil. Fixed oils are 
volatilized by a strong heat, and when volati- 
lized, take lire by the contact of an ignited 
body. When added to acids, they attract 
oxy gen from the acids, and form a kind of 
resinous substance. With alkalis, they form 
soap ; and dissolve sulphur and phosphorus. 
Volatile oils are generally procured by dis- 
tilling aromatic plants with water. The. 
water rises, accompanied by. the oil, part 
of which is dissolved in tire water ; but the 
greatest quantity separates to the surface, or 
the bottom. They are soluble in alcohol, dis- 
solve resin, sulphur, and phosphorus, and 
are very inflammable. They attract oxygen ; 
and by long keeping are converted into resin, 
charcoal, and water. See Oil. 
3. Resins exist in the vessels of certain 
trees, and frequently exude from them spon- 
taneously. Sometimes they are procured by 
making incisions in the trees, and some- 
times by distilling the wood. They are con- 
sidered as volatile oils combined with oxygen. 
They' are soluble in alcohol and oils, but not 
in water. It is this property that renders them 
so valuable as varnishes. They are inflam- 
mable, and melt with a slight heat. The 
principal resins are the turpentines, mastic, 
copal, sandarac, &c. See Resins, &c. 
4. Gum resins appear to be a natural mix- 
ture of resin and mucilage. They are partly 
soluble in water, and partly in alcohol. Gum 
ammoniac, assafeetida, See. are gum resins. 
Sec Gum. 
5. Caoutchouc, or elastic gum, very much 
resembles a resin. It is very elastic, in- 
flammable, and insoluble in water or fat. 
It is partly soluble in volatile oils, and entirely 
so in melted spermaceti, and in nitric ether. 
It gives out heat as often as it returns to its 
dimensions after strong tension. See Ca- 
outchouc. 
6. Camphor is a volatile oil, rendered con- 
crete by carbon. It is very inflammable, and 
sublimes by a gentle heat. It is soluble in 
ether, alcohol, acids, and oils, ft is highly 
odorous, and has been supposed to prevent 
the spreading of contagious disorders ; but this 
has been denied by some. See Camphor. 
7. Wax is a vegetable substance, found in 
the greatest quantity on the anthers of flow- , 
ers. The surfaces of many leaves are also 
coated with it. It is collected by the bees. 
It is insoluble in water and alcohol, but solu-, 
ble in volatile and fixed oils. It is very in- 
flammable. Its principles are the same as 
those of volatile oil. See Wax. 
8. Iioney is chiefly formed in the pistils or 
female organs of flowers, whence it is collect- , 
ed by the bees. It appears to be sugar dis- 
solved in mucilage, See Honey. 
9. Sugar is very extensively distributed 
through the vegetable 'kingdom. It is pro- 
cured in the greatest quantity horn the sugar- 
cane ; but it may also be obtained from the 
sugar-maple, the beet-root, carrots, &c. Its 
constituent principles are oxygen, carbon, : 
and hydrogen. See Sugar. 
10. Gluten is an elastic substance, very 
much resembling an animal matter, found in 
many vegetables, but chiefly in wheat-flour. 
It is insoluble in water, and very slightly so in 
alcohol. It hardens by heat iato a brownish 
transparent horny matter ; and differs from 
all .other vegetable substances by its contain- 
ing a larger quantity of nitrogen and some 
ammonia. 
1 1 . Fecula, or starch, forms the principal 
part of the substance which is washed away in 
order to obtain the gluten from the grain. 
W hen the fluid is suffered to stand, a white 
powder subsides, which is the starch. It is 
not soluble in cold water nor in alcohol ; but 
it is soluble in hot water, forming with it a 
well-known paste. Barley consists almost 
entirely of it. It appears to be only a slight 
alteration from mucilage, differing from that 
only by its being insoluble in cold water. 
There are also coloured fecula', as indigo. 
12. Tannin, or the tanning principle, is 
found in the bark of trees, and all those 
parts of vegetables which are called astrin- 
gent. It has the property of forming a com- 
pound with gelatine or animal jelly that 
is solid, elastic, and insoluble in water. On 
its combination in this manner with the gela- 
tinous part of skin, depends the art of tanning 
or making leather. See Cutis. 
13. W oody fibre constitutes the basis of 
wood. It may be procured separate from 
every other substance, by boiling wood- 
shavings in water to dissolve the extractive 
matter, and then in alcohol to separate the 
resins, &:c. It is insipid, insoluble in water, 
and combustible. W hen heated without ac- 
cess of air, it is converted into charcoal, 
which lias been already described. 
14. Colouring matter is found in veget- 
ables combined with, 1, the extractive prin- 
ciple; 2. with resin; 3. with fecula ; 4. gum. 
The greater part of the colouring matters 
have a great affinity for many of the 
earths, but chiefly for alumina ; also for the 
white metallic oxyds, particularly oxyd of 
tin ; and also for animal fibrous matters, and 
for oxygen. On these properties, and the 
methods of transferring the colouring princi- 
ple of one body to another so that it shall he 
durably fixed, depends the whole art of dye- 
ing. See Dyeing. 
15. Acids. The acids which exist ready 
formed in vegetables, are the citric, malic, 
oxalic, gallic, benzoic, tartaric, acetic, and 
suberic. They have been already described. 
lti. Besides the substances already enume- 
rated, many others are found in vegetables, 
such as sulphur, iron, manganese, lime, 
alumina, magnesia, barytes, &c. All the ve- 
getables of the class. called gramma, or grasses, 
have an epidermis or outer skin, composed of 
silex. ibis is particularly observable in 
canes, which, when struck together in the 
dark, produce sparks of fire. 
Vinous fermentation . — If mucilaginous sac- 
charine vegetable substances, under a proper 
combination of water and heat (from 60 to 70° 
Fahrenheit), are not entirely excluded from 
air, they experience in a very short time a 
striking change in their mixture. An internal 
commotion takes place ; the mass grows tur- 
bid ; a large quantity of air-bubbles are dis- 
charged from its inner part, which, on ac- 
count of the toughness of the matter wherein 
they are inclosed, form a stratum on the sur- 
face of the fluid, known by the name of yeast. 
These air-bubbles consist of.carbonic acid gas. 
After a time these appearances cease; the 
fermented liquor becomes clear and transpa- 
rent, and no more gas is disengaged, 'the 
liquor now has lost its sweetness and visci- 
dity, and has acquired the vinous taste. awi. 
