GUM. 
of 11 ie lichens; the seeds of flax, quinces, 
fenugrec, &c. 
The bulbs of the hyacinth contain so much 
mucilage, that when dried they may be em- 
ployed as a substitute for gum arabie. This 
Vvas first made known to the public by Mr. 
Willis. A mucilage may be extracted' from 
most of the stringy lichens by water, which 
likewise answers ail the purposes of a solution 
of gurn. This was first discovered by lord 
Dundonald. The mucilaginous quality of 
most of the fuci is apparently much greater, 
though the mucilage obtained from them 
does not answer so well. 
- How far the mucilage extracted by water 
from these plants agrees with gum in its pro- 
perties, has not been examined with much 
recision, if we except the mucilage of the 
yacinth. From the experiments of Le~ 
roux, it appears that the mucilage of that 
plant is in every respect the same with gum. 
'Fhe bulbs are to be pounded, mixed with 
five times their weight of water, and subject- 
ed to the press. The residue is to be diluted 
afresh, and again pressed. The liquid thus 
obtained is to be allowed to repose for some 
days till it clarifies somewhat, and then eva- 
porated to dryness. The gum remains. 
8. It has been remarked by Mr. Barrow, 
•and probably also by others, that all the 
plants which yield gum have an astringent 
bark. This rule, however, does not- hold j 
with respect to mucilage. Almost ail the 
trees known to yield gum have been enu- 
merated in the preceding part of this article. 
To attempt a list of all the plants containing 
mucilage, would, in the present state of our 
knowledge, be superfluous, even if it was pos- 
sible. It exists most abundantly in young 
plants, and gradually disappears as they ar- 
rive at perfection. ’It forms a great propor- 
tion of the leaves and roots of many eatable 
plants. 
9. Gum is a very nutritive food, though 
Seldom employed for that purpose, except 
when in the state of mucilage. It is used 
frequently as a paste, and to give stiffness or 
lustre to linen. The calico-printers use it 
in great quantities to give their colours such 
a degree of consistency as prevents them 
from running upon the cloth. It forms an 
ingredient in ink for a similar reason. In 
medicine it forms the base of many mixtures. 
Gum-resins. This class of vegetable 
substances has been long distinguished by 
physicians and apothecaries. It contains 
many active substances much employed in 
medicine; and they certainly possess a suf- 
ficient number of peculiar properties to en- 
title them to be ranked apart. Unfortunate- 
ly these substances have not yet attracted 
much of the attention of chemists. Their 
properties and constituents of course are but 
imperfectly ascertained. They may, how- 
ever, be distinguished by fhe following cha- 
racters. 
They are usually opaque, or at least their 
transparency is inferior to that of the resins. 
They are always solid, and most commonly 
very brittle, and have sometimes a fatty ap- 
pearance. 
When heated they do not melt as the re- 
sins do, neither are they so combustible. 
Heat, however, commonly softens them, and 
causes them to swell. They burn with a 
flame. They have almost always a strong 
smell, w hich in several instances is alliaceous. 
Their taste also is often acrid, and always 
much stronger than that of the resins. r l hey 
are partially soluble in water; but the solution 
is always opaque, and usually milky. 
Alcohol dissolves only a portion of them . 
The solution, is transparent; but when di- 
luted with water it becomes milky; yet no 
precipitate falls, nor is any thing obtained by 
iiltring the solution. Vinegar and wine 
likewise dissolve them partially ; and the so- 
lution, like the aqueous, is opaque or milky. 
The action of alkalies on them has been 
examined only by Mr. Hatchett. All of 
them tried by that celebrated chemist dis- 
solved readily in alkaline solutions when as- 
sisted by heat. We may therefore consider 
them as soluble in alkalies like resins. Mr. 
Hatchett also found them acted on by nitric 
acid, and dissolved by it just as the resinous 
bodies. 
Their specific gravity is usually greater 
than that of the resins. * Their other proper- 
ties still continue unknown. They all either 
exude spontaneously from plants, or are ob- 
tained by incisions. At first they seem tb 
be in a’ liquid state; but they gradually 
harden when exposed to the air and weather. 
They have been usually considered by 
chemists as composed of gum and resin ; but 
their properties are not consistent with that 
supposition. They all contain a volatile oil, 
or a substance intermediate between an oil 
and resin. To this substance w e are to as- 
cribe the milky solution which they form 
with water. The other constituent, in most 
cases, bears a much closer resemblance to 
extractive than to gum ; perhaps, then, w e 
shall not err very far, if we consider the gum- 
resins as composed of a gum or an extractive 
substance, and a body intermediate between 
oil and resin ; to which last they owe their 
most peculiar properties. 
The gum-resins which have been hitherto 
applied to any useful purpose are chiefly the 
follow ing : 
1. Galbaminu It is obtained from the 
bubon galbui'uin, a perennial plant, and a 
native of Africa. When this plant is cut 
j across a little above the root, a milky juice 
j flows out, which soon hardens and consti- 
tutes galbanum. It comes to this country 
from the Levant in small pieces composed 
of tears, agglutinated together of a yellowish 
or white colour. Its taste is acrid and bitter, 
and its smell peculiar. Water, vinegar, and 
wine, dissolve most of it, but the solution is 
milky. Alcohol acts but feebly ; when dis- 
tilled it yields volatile oil in considerable 
quantity. Its specific gravity is 1 .2. 
2. Ammoniac. This substance is brought 
from the East Indies. Nothing certain is 
known concerning the plant which yields it ; 
though from analogy it has been suspected 
to be a species of ferula. It is in small pie- 
ces, and has a yellowish-white colour. Its 
smell is somewhat like that of galbanum, 
but more pleasant ; its taste is a nauseous 
sweet mixed with bitter. It does not melt. 
Water dissolves a portion of it ; the solution 
is milky, but gradually lets fall a resinous 
portion. One-half is soluble in alcohol. It 
seems then to contain resin completely form- 
ed: specific gravity is 1.2. Mr. Hatchett 
found it soluble in alkalies. 
3. Olibanum, is obtained from the juni- 
perus lycia, and is chiefly collected in Arabia. 
5 T2 
883 
It is the frankincense of the anti cuts ; it is in 
transparent brittle masses about the size of 
a chesnut. Its colour is yellow. It has 
little taste ; and when burnt diffuses an agree- 
able odour. Alcohol dissolves it ; and with 
water it forms a milky liquid. W hen dis- 
tilled it yields a little volatile oil. Its spe- 
cific gravity is 1.173. 
4. Sagapanuir. The plant which yields 
this gum-resin is not well known; but it is 
suspected to be the ferula persica. The sub- 
stance itself is brought to Europe from Alex- 
andria. It is commonly in tears aggluti- 
nated together : colour yellow ; taste hot and 
bitter; smell alliaceous ; softens between the 
ringers, but does not melt when heated: spa- 
ringly soluble in water, but almost completely 
soluble in alcohol. When distilled it yields 
a volatile oil, 
5. Asafcctida. This substance, is obtained 
from the ferula asafoetida, a perennial plant 
which is a native of Persia. When the plant 
is about four years old, its roots are dug up 
and cleaned. Their extremity being then 
cut off, a milky juice exudes, which is col- 
lected. Then another portion is cut off, and 
more juice exudes. This is continued till 
the roots are exhausted. The juice thus col- 
lected soon hardens, and constitutes asa- 
fcetida. It comes to Europe in small grains 
of different colours, whitish, reddish, violet* 
brown: pretty hard, but brittle: its taste is 
acrid and bitter ; its smell strongly alliaceous 
and foetid. It is imperfectly soluble both iw 
alcohol and water ; but, like the other gum- 
resins, has been but carelessly analysed. Its 
specific gravity is 1.327. 
6. Scanvnom/. This substance is obtained 
from the convolvulus scammonia, a climbing 
plant which grows in Persia. The roots 
when cut yield a milky juice ; this when col- 
lected and allowed to harden constitutes 
scammony. Colour, dark grey; smell, pe- 
culiar and nauseous ; taste, bitter and acrid : 
with water it forms a greenish-coloured 
opaque liquid. Alcohol dissolves the greatest 
part of it; it is usually mixed with the ex- 
pressed juice of the root, and frequently also 
with other impurities, which alter its appear- 
ance. In medicine it operates as a strong 
cathartic. Its specific gravity is 1.235. 
7. Opopona; c. This substance is obtained 
from the pastinaca opoponax, a plant which 
is a native of the countries round the Levant, 
The gum resin, like most others, is obtained 
by wounding the roots of the plant. The 
milky juice when dried in the sun constitutes 
the opoponax. It is in lumps of a reddish 
yellow colour, and white within; smell pe- 
culiar; taste bitter and acrid; with water it 
forms a milky solution. Its specific gravity 
is 1.622. 
8. Gamboge, or gumgutt. This substance is 
obtained from the stalagmitis cambogioides^ 
a tree which grows wild in the East Indies, 
In Siam it is obtained in drops by wounding 
the shoots ; in Ceylon it exudes from wounds 
of the bark. It is brought to Europe in large 
cakes. Its colour is yellow ; it is opaque, 
brittle, and breaks vitreous ; it has no smell, 
and very little taste ; with water it forms a 
yellow turbid liquid. Alcohol dissolves it 
almost completely : and when mixed with wa- 
ter it becomes turbid, unless the solution con- 
tains ammonia ; in that case acids throw dow h 
an insoluble yellow precipitate. It operates. 
