GEL 
stable exhibits the' effect of different earthy 
solutions when mixed with- a pretty concen- 
trated solution of common glue. 
Substances. 
Effects. 
.Lime water • 
Strontian water 
Barytes water 
Muriat of barytes 
I Silicated potass - 
. Alummated potass 
Oxalat of ammonia 
Phosphat of soda 
No change. 
No change. 
Became milky. Precipit. 
not dissolved by acetic 
acid. 
The same as the last. 
No change. 
No change 
Became milky. 
Became slightly milky. 
The milkiness produced by some of these 
re-agents was not owing to their effect upon 
the gelatine, but upon the lime and the sul- 
phuric acid which it contained. 
The metals jn their pure state have no 
effect upon gelatine; but several of 'the me- 
tallic oxides, when agitated in a solution of 
gelatine, have the property of depriving the 
water of the greatest part of that body, with 
which Uiey form an insoluble compound. Se- 
veral of the metallic salts likewise precipitate 
gelatine from water. The following table 
exhibits the result of mixing various metallic 
.salts with a concentrated solution of gelatine, 
as far as experiments have gone. 
Metallic Solutions. 
Nitromuriat of gold 
Nitrat of silver 
Nitrat of mercury - 
Oxymuriat of mercury 
Sup. oxysuiphat of mer, 
Dry oxysuiphat of mer. 
Prussiat of mercury 
Oxvnitrat of copper 
Muriat of copper 
Oxysuiphat of copper 
Cuprat of ammonia 
Sulphat of iron 
Oxysuiphat of iron 
Oxynitrat of iron 
Oxymuriat of iron 
Effects. 
l. copious yellowish- 
whitc precipitate. So- 
luble by adding water. 
Becomes slightly milky. 
A very copious curdy 
precipitate. 
A copious white precip. 
No change. 
Crystals become yellow, 
white flakes- appear, 
and the liquid be- 
comes transparent. 
No change. 
No change. 
Becomes milky. 
No change. 
No change. 
Nitromuriat of tin 
Oxymuriat of tin 
Nitrat of lead 
Acetat of lead 
Plumbat of potass - 
Plumbat of lime 
No change. 
Becomes slowly milky. 
No change. 
Muriat of zinc - No change. 
A few yellow flakes ap- 
pear. 
Becomes slightly milky, 
as when alcohol is 
added. 
Assumes a pink colour. 
Becomes green. 
Muriat of antimony A copious flaky precip. 
Tartar emetic - - |No change. 
Nitrat of bismuth pre- 
cipitable by watgr Becomes milky. 
Ditto, not precipitable’ 
by water - - [No change. 
Muriat of arsenic - [No change. 
G E L 
Gelatine Is insoluble in alcohol. When 
alcohol is mixed with a solution of gelatine, 
the mixture becomes milky, but becomes 
again transparent when agitated, unless the 
solution is concentrated, and the quantity of 
alcohol considerable. Gelatine is most pro- 
bably equally insoluble in ether. 
When the solution of tan is dropped into 
gelatine, a copious white precipitate appears, 
which soon forms an elastic adhesive mass, 
not unlike vegetable gluten. This precipi- 
tate is composed of gelatine and tan ; it soon 
dries in the open air, and forms a brittle re- 
sinous-like substance, insoluble in water, ca- 
pable of resisting the greater number of che- 
mical agents, and not susceptible of putrefac- 
tion. It resembles exactly overtanned lea- 
ther. The precipitate is soluble in the solu- 
tion of gelatine, as Mr. Davy first observed. 
Neither is the whole tan thrown down, unless 
the solutions both of tan and gelatine are 
somewhat concentrated. Tremulous, gela- 
tine, as was. first observed by the same che- 
mist, does not precipitate tan; but if we em- 
ploy a solution of gelatine so strong that it 
gelatinizes when cold, and heated till it be- 
come:- quite liquid, it answers best of all for 
throw ing down tan. It is by this property of 
forming a white precipitate with tan that ge- 
latine is usually detected in animal fluids. It 
is not, however, a perfectly decisive test, 
as there are two other animal substances 
namely, albumen and mucilage, which are 
thrown down likewise by tan. Gelatine 
does not, properly speaking., combine with 
oils, but it renders them miscible with water, 
and forms a kind of emulsion. 
From the effects of different reagents on 
gelatine, and from the decomposition which 
it undergoes when heated, we see that it con- 
tains carbon, hydrogen, azote, and oxygen. 
But what the proportion of these constituents 
is, cannot be easily ascertained. The phos- 
phat of lime, and the traces of soda, which it 
always yields, are most likely only held in 
solution by it. 
Gelatine, like all other constituents of ani- 
mal bodies, is susceptible of numerous shades 
of variations in its properties, and of course 
is divisible into an indefinite number of spe- 
cies. Several of these have been long known 
and manufactured-for different purposes ; and 
many curious varieties have been pointed out 
bv Mr. Hatchett, in his admirable disserta- 
tions on shell, bone, and zoophytes, publish- 
ed in the Philosophical Transactions for 1797 
and 1800. The most important species are 
the following : 
1. Glue . — This well-known substance has 
been long manufactured in most countries, 
'and employed to cement pieces of wood to- 
gether. It is extracted by water from animal 
substances, and differs in its qualities accord- 
ing to the substances employed. Bones, mus- 
cles, tendons, ligaments, membranes, and 
skins, all yield it ; but the quality is best when 
skins are employed; and those of old animals 
yield a much stronger glue than those of 
young animals. English glue is considered 
as the best, owing to the care with which it is 
made. The parings of hides, pelts from fur- 
riers, the hoofs and ears of horses, oxen, 
calves, sheep, &c. are the substances from 
which it is extracted in Britain, and quanti- 
ties of these substances are imported for the 
purpose. They are first digested iii lime- 
5 M 2 
G E L 
62;. 
water to clean them, then steeped in clean 
water, laid in a heap till the water runs otl, 
and then boiled in brass caldrons with pure 
water. The impurities are skimmed od as 
they rise ; and when the whole is dissolved, a 
little alum or finely-powdered lime is thrown 
in. The skimming having been continued 
for some time, the whole is strained through 
baskets, and allowed to settle. 1 he clear 
liquid is gently poured back into the kettle, 
boiled a second time, and skimmed till it is 
reduced to the proper consistency. It is 
then poured into large frames, where it con- 
cretes on cooling, into a jelly. It is cut by a 
spade into square cakes, which are again cut 
by means of a wire into thin slices; these 
slices are put into a kind of coarse net-work, 
and dried in the open air. The best glue is- 
extremely hard and brittle ; it has a dark- 
brown colour, and an equal degree of trans- 
parency without black spots. \\ hen put 
into cold water, it swells very much, and be- 
comes gelatinous, but does not dissolve. 
When glue is soluble in cold water, it is a 
proof that it wants strength. 
2. Size . — This substance differs from glue 
in being colourless, and more transparent. 
It is manufactured in the same way, but with 
more care; eel-skins, vellum, parchment, 
some kinds of white leather, and the skins ot 
horses, cats, and rabbits, are the substitutes 
from which it is procured. It is commonly in- 
rior to glue in strength. It is employed by 
paper-makers to give strength to that article, 
and likewise by linen-manufacturers, gilders, 
polishers, painters in fresco, &c. 
3. Isinglass . — This substance agrees with 
size in being transparent, but it is much finer, 
and is therefore sometimes employed as an 
article of food. It is prepared in Russia 
from the air-bladders and sounds of different 
kinds of fish which occur in lire mouths of 
large rivers; chiefly different species of acci- 
penser, as the sturio, stellatus, huso, ruthe- 
nus, and likewise the siluris glaris. The blad- 
der is taken from the fish, clean washed, the 
exterior membrane separated, cut lengthwise 
and formed into rolls, and then dried in the 
open air. When good, isinglass is ot a white 
colour, semitransparent, and dry. It dissolves 
in water with more difficulty than glue, pro- 
bably because it is not formed originally by 
solution. It differs from common glue in 
being soluble in alcohol. From the analysis 
of isinglass, by Mr. Hatchett, we learn that it 
is almost completely convertible into gelatine 
by solution and boiling. 500 grains of it left 
by incineration 1.5 grains of phosphat of soda 
mi.xtfd with a little phosphat of lime. 
A coarse kind of isinglass is prepared from 
sea-wolves, porpoises, sharks, cuttle-fish, 
whales, and all fish without scales. The 
head, tail, and fins of these, are boiled in wa- 
ter, and concentrated by evaporation, till it 
gelatinizes on cooling: if is then cast into flat: 
slabs, and cut into tablets. This species is 
used for clarifying, stiffening silk, making 
sticking-plaster, and other purposes. 
Gelatine exists in great abundance in ani- 
mals, forming .the constituent part ot their 
solid and fluid parts. Its uses ure numerous. 
In a state of jelly it constitutes one of tin: 
most nourishing and palatable species of 
food. 
GELATINOUS, in pharmacy and medi- 
cine, any thing approaching to the glutinous 
consistence ot a gelatine, or jelly. 
