[1] This fat contains a small quantity of solvent, which is removed
by heating with steam, when the solvent distils off. Hot water is
then run in to melt the fat, which rises to the surface of the water
and is floated off. Another boiling with water, and again floating
off, frees the fat from dirt and mineral matter, and the product is
ready for casking.
[2] The residue in the extractors is usually dried in steam-heated
vessels, and mixed with potassium and magnesium salts; the product is
then put on the market as fish-potash guano.
GLUTARIC ACID, or NORMAL PYROTARIC ACID, HO2C.CH2.CH2.CH2.CO2H, an
organic acid prepared by the reduction of [alpha]-oxyglutaric acid with
hydriodic acid, by reducing glutaconic acid, HO2C.CH2.CH:CH.CO2H, with
sodium amalgam, by conversion of trimethylene bromide into the cyanide
and hydrolysis of this compound, or from acetoacetic ester, which, in
the form of its sodium derivative, condenses with [beta]-iodopropionic
ester to form acetoglutaric ester, CH3.CO.CH(CO2C2H5).CH2.CH2.CO2C2H5,
from which glutaric acid is obtained by hydrolysis. It is also obtained
when sebacic, stearic and oleic acids are oxidized with nitric acid. It
crystallizes in large monoclinic prisms which melt at 97.5 deg. C., and
distils between 302 deg. and 304 deg. C., practically without
decomposition. It is soluble in water, alcohol and ether. By long
heating the acid is converted into its anhydride, which, however, is
obtained more readily by heating the silver salt of the acid with acetyl
chloride. By distillation of the ammonium salt glutarimide,
CH2(CH2.CO)2NH, is obtained; it forms small crystals melting at 151 deg.
to 152 deg. C. and sublimes unchanged.
On the alkyl glutaric acids, see C. Hell (_Ber._, 1889, 22, pp. 48,
60), C. A. Bischoff (_Ber._, 1891, 24, p. 1041), K. Auwers (_Ber._,
1891, 24, p. 1923) and W. H. Perkin, junr. (_Journ. Chem. Soc._, 1896,
69, p. 268).
GLUTEN, a tough, tenacious, ductile, somewhat elastic, nearly tasteless
and greyish-yellow albuminous substance, obtained from the flour of
wheat by washing in water, in which it is insoluble. Gluten, when dried,
loses about two-thirds of its weight, becoming brittle and
semi-transparent; when strongly heated it crackles and swells, and burns
like feather or horn. It is soluble in strong acetic acid, and in
caustic alkalis, which latter may be used for the purification of starch
in which it is present. When treated with .1 to .2% solution of
hydrochloric acid it swells up, and at length forms a liquid resembling
a solution of albumin, and laevorotatory as regards polarized light.
Moistened with water and exposed to the air gluten putrefies, and
evolves carbon dioxide, hydrogen and sulphuretted hydrogen, and in the
end is almost entirely resolved into a liquid, which contains leucin and
ammonium phosphate and acetate. On analysis gluten shows a composition
of about 53% of carbon, 7% of hydrogen, and nitrogen 15 to 18%, besides
oxygen, and about 1% of sulphur, and a small quantity of inorganic
matter. According to H. Ritthausen it is a mixture of _glutencasein_
(Liebig's vegetable fibrin), _glutenfibrin_, _gliadin_ (Pflanzenleim),
_glutin_ or vegetable gelatin, and _mucedin_, which are all closely
allied to one another in chemical composition. It is the gliadin which
confers upon gluten its capacity of cohering to form elastic masses, and
of separating readily from associated starch. In the so-called gluten of
the flour of barley, rye and maize, this body is absent (H. Ritthausen
and U. Kreusler). The gluten yielded by wheat which has undergone
fermentation or has begun to sprout is devoid of toughness and
elasticity. These qualities can be restored to it by kneading with salt,
lime-water or alum. Gluten is employed in the manufacture of gluten
bread and biscuits for the diabetic, and of chocolate, and also in the
adulteration of tea and coffee. For making bread it must be used fresh,
as otherwise it decomposes, and does not knead well. Granulated gluten
is a kind of vermicelli, made in some starch manufactories by mixing
fresh gluten with twice its weight of flour, and granulating by means of
a cylinder and contained stirrer, each armed with spikes, and revolving
in opposite directions. The process is completed by the drying and
sifting of the granules.
GLUTTON, or WOLVERINE (_Gulo luscus_), a carnivorous mammal belonging to
the _Mustelidae_, or weasel family, and the sole representative of its
genus. The legs are short and stout, with large feet, the toes of which
terminate in strong, sharp claws considerably curved. The mode of
progression is semi-plantigrade. In size and form the glutton is
something like the badger, measuring from 2 to 3 ft. in length,
exclusive of the thick bushy tail, which is about 8 in. long. The head
is broad, the eyes are small and the back arched. The fur consists of an
undergrowth of short woolly hair, mixed with long straight hairs, to the
abundance and length of which on the sides and tail the creature owes
its shaggy appearance. The colour of the fur is blackish-brown, with a
broad band of chestnut stretching from the shoulders along each side of
the body, the two meeting near the root of the tail. Unlike the majority
of arctic animals, the fur of the glutton in winter grows darker. Like
other _Mustelidae_, the glutton is provided with anal glands, which
secrete a yellowish fluid possessing a highly foetid odour. It is a
boreal animal, inhabiting the northern regions of both hemispheres, but
most abundant in the circumpolar area of the New World, where it occurs
throughout the British provinces and Alaska, being specially numerous in
the neighbourhood of the Mackenzie river, and extending southwards as
far as New York and the Rocky Mountains. The wolverine is a voracious
animal, and also one with an inquisitive disposition. It feeds on
grouse, the smaller rodents and foxes, which it digs from their burrows
during the breeding-season; but want of activity renders it dependent
for most of its food on dead carcases, which it frequently obtains by
methods that have made it peculiarly obnoxious to the hunter and
trapper. Should the hunter, after succeeding in killing his game, leave
the carcase insufficiently protected for more than a single night, the
glutton, whose fear of snares is sufficient to prevent him from touching
it during the first night, will, if possible, get at and devour what he
can on the second, hiding the remainder beneath the snow. It annoys the
trapper by following up his lines of marten-traps, often extending to a
length of 40 to 50 m., each of which it enters from behind, extracting
the bait, pulling up the traps, and devouring or concealing the
entrapped martens. So persistent is the glutton in this practice, when
once it discovers a line of traps, that its extermination along the
trapper's route is a necessary preliminary to the success of his
business. This is no easy task, as the glutton is too cunning to be
caught by the methods successfully employed on the other members of the
weasel family. The trap generally used for this purpose is made to
resemble a cache, or hidden store of food, such as the Indians and
hunters are in the habit of forming, the discovery and rifling of which
is one of the glutton's most congenial occupations--the bait, instead of
being paraded as in most traps, being carefully concealed, to lull the
knowing beast's suspicions. One of the most prominent characteristics of
the wolverine is its propensity to steal and hide things, not merely
food which it might afterwards need, or traps which it regards as
enemies, but articles which cannot possibly have any interest except
that of curiosity. The following instance of this is quoted by Dr E.
Coues in his work on the _Fur-bearing Animals of North America_: "A
hunter and his family having left their lodge unguarded during their
absence, on their return found it completely gutted--the walls were
there, but nothing else. Blankets, guns, kettles, axes, cans, knives and
all the other paraphernalia of a trapper's tent had vanished, and the
tracks left by the beast showed who had been the thief. The family set
to work, and, by carefully following up all his paths, recovered, with
some trifling exceptions, the whole of the lost property." The cunning
displayed by the glutton in unravelling the snares set for it forms at
once the admiration and despair of every trapper, while its great
strength and ferocity render it a dangerous antagonist to animals larger
than itself, occasionally including man. The rutting-season occurs in
March, and the female, secure in her burrow, produces her young--four or
five at a birth--in June or July. In defence of these, she is
exceedingly bold, and the Indians, according to Dr Coues, "have been
heard to say that they would sooner encounter a she-bear with her cubs
than a carcajou (the Indian name of the glutton) under the same
circumstances." On catching sight of its enemy, man, the wolverine
before finally determining on flight, is said to sit on its haunches,
and, in order to get a clearer view of the danger, shade its eyes with
one of its fore-paws. When pressed for food it becomes fearless, and has
been known to come on board an ice-bound vessel, and in presence of the
crew seize a can of meat. The glutton is valuable for its fur, which,
when several skins are sewn together, forms elegant hearth and carriage
rugs. (R. L.*)
[Illustration: The Glutton, or Wolverine (_Gulo luscus_).]
GLYCAS, MICHAEL, Byzantine historian (according to some a Sicilian,
according to others a Corfiote), flourished during the 12th century A.D.
His chief work is his _Chronicle_ of events from the creation of the
world to the death of Alexius I. Comnenus(1118). It is extremely brief
and written in a popular style, but too much space is devoted to
theological and scientific matters. Glycas was also the author of a
theological treatise and a number of letters on theological questions. A
poem of some 600 "political" verses, written during his imprisonment on
a charge of slandering a neighbour and containing an appeal to the
emperor Manuel, is still extant. The exact nature of his offence is not
known, but the answer to his appeal was that he was deprived of his
eyesight by the emperor's orders.
Editions: "Chronicle and Letters," in J. P. Migne, _Patrologia
Graeca_, clviii.; poem in E. Legrand, _Bibliotheque grecque vulgaire_,
i.; see also F. Hirsch, _Byzantinische Studien_ (1876); C. Krumbacher
in _Sitzungsberichte bayer. Acad._, 1894; C. F. Bahr in Ersch and
Gruber's _Allgemeine Encyklopadie_.
GLYCERIN, GLYCERINE or GLYCEROL (in pharmacy _Glycerinum_) (from Gr.
[Greek: glykys], sweet), a trihydric alcohol, trihydroxypropane,
C3H5(OH)3. It is obtainable from most natural fatty bodies by the action
of alkalis and similar reagents, whereby the fats are decomposed, water
being taken up, and glycerin being formed together with the alkaline
salt of some particular acid (varying with the nature of the fat). Owing
to their possession of this common property, these natural fatty bodies
and various artificial derivatives of glycerin, which behave in the same
way when treated with alkalis, are known as glycerides. In the ordinary
process of soap-making the glycerin remains dissolved in the aqueous
liquors from which the soap is separated.
Glycerin was discovered in 1779 by K. W. Scheele and named _Olsuss_
(_principe doux des huiles_--sweet principle of oils), and more fully
investigated subsequently by M. E. Chevreul, who named it glycerin, M.
P. E. Berthelot, and many other chemists, from whose researches it
results that glycerin is a trihydric alcohol indicated by the formula
C3H5(OH)3, the natural fats and oils, and the glycerides generally,
being substances of the nature of compound esters formed from glycerin
by the replacement of the hydrogen of the OH groups by the radicals of
certain acids, called for that reason "fatty acids." The relationship of
these glycerides to glycerin is shown by the series of bodies formed
from glycerin by replacement of hydrogen by "stearyl" (C18H35O), the
radical of stearic acid (C18H35O.OH):--
Glycerin. Monostearin. Distearin. Tristearin.
CH2.OH CH2.O(C18H35O) CH2.O(C18H35O) CH2.O(C18H35O)
| | | |
CH.OH CH.OH CH.O(C18H35O) CH.O(C18H35O)
| | | |
CH2.OH CH2.OH CH2.OH CH2.O(C18H35O)
The process of saponification may be viewed as the gradual progressive
transformation of tristearin, or some analogously constituted substance,
into distearin, monostearin and glycerin, or as the similar
transformation of a substance analogous to distearin or to monostearin
into glycerin. If the reaction is brought about in presence of an
alkali, the acid set free becomes transformed into the corresponding
alkaline salt; but if the decomposition is effected without the presence
of an alkali (i.e. by means of water alone or by an acid), the acid set
free and the glycerin are obtained together in a form which usually
admits of their ready separation. It is noticeable that with few
exceptions the fatty and oily matters occurring in nature are substances
analogous to tristearin, i.e. they are trebly replaced glycerins.
Amongst these glycerides may be mentioned the following:
_Tristearin_--C3H5(O.C18H35O)3. The chief constituent of hard animal
fats, such as beef and mutton tallow, &c.; also contained in many
vegetable fats in smaller quantity.
_Triolein_--C3H5(O.C18H33O)3. Largely present in olive oil and other
saponifiable vegetable oils and soft fats; also present in animal
fats, especially hog's lard.
_Tripalmitin_--C3H5(O.C16H31O)3. The chief constituent of palm oil;
also contained in greater or less quantities in human fat, olive oil,
and other animal and vegetable fats.
_Triricinolein_--C3H5(O.C18H33O2)3. The main constituent of castor
oil.
Other analogous glycerides are apparently contained in greater or
smaller quantity in certain other oils. Thus in cows' butter,
_tributyrin_, C3H5(O.C4H7O)3, and the analogous glycerides of other
readily volatile acids closely resembling butyric acid, are present in
small quantity; the production of these acids on saponification and
distillation with dilute sulphuric acid is utilized as a test of a
purity of butter as sold. _Triacetin_, C3H5(O.C2H3O)3, is apparently
contained in cod-liver oil. Some other glycerides isolated from natural
sources are analogous in composition to tristearin, but with this
difference, that the three radicals which replace hydrogen in glycerin
are not all identical; thus kephalin, myelin and lecithin are glycerides
in which two hydrogens are replaced by fatty acid radicals, and the
third by a complex phosphoric acid derivative.
Glycerin is also a product of certain kinds of fermentation, especially
of the alcoholic fermentation of sugar; consequently it is a constituent
of many wines and other fermented liquors. According to Louis Pasteur,
about 1/30th of the sugar transformed under ordinary conditions in the
fermentation of grape juice and similar saccharine liquids into alcohol
and other products become converted into glycerin. In certain natural
fatty substances, e.g. palm oil, it exists in the free state, so that it
can be separated by washing with boiling water, which dissolves the
glycerin but not the fatty glycerides.
_Properties._--Glycerin is a viscid, colourless liquid of sp. gr. 1.265
at 15 deg. C., possessing a somewhat sweet taste; below 0 deg. C. it
solidifies to a white crystalline mass, which melts at 17 deg. C. When
heated alone it partially volatilizes, but the greater part decomposes;
under a pressure of 12 mm. of mercury it boils at 170 deg. C. In an
atmosphere of steam it distils without decomposition under ordinary
barometric pressure. It dissolves readily in water and alcohol in all
proportions, but is insoluble in ether. It possesses considerable
solvent powers, whence it is employed for numerous purposes in pharmacy
and the arts. Its viscid character, and its non-liability to dry and
harden by exposure to air, also fit it for various other uses, such as
lubrication, &c., whilst its peculiar physical characters, enabling it
to blend with either aqueous or oily matters under certain
circumstances, render it a useful ingredient in a large number of
products of varied kinds.
_Manufacture._--The simplest modes of preparing pure glycerin are
based on the saponification of fats, either by alkalis or by
superheated steam, and on the circumstance that, although glycerin
cannot be distilled by itself under the ordinary pressure without
decomposition, it can be readily volatilized in a current of
superheated steam. Commercial glycerin is mostly obtained from the
"spent lyes" of the soap-maker. In the van Ruymbeke process the spent
lyes are allowed to settle, and then treated with "persulphate of
iron," the exact composition of which is a trade secret, but it is
possibly a mixture of ferric and ferrous sulphates. Ferric hydrate,
iron soaps and all insoluble impurities are precipitated. The liquid
is filter-pressed, and any excess of iron in the filtrate is
precipitated by the careful addition of caustic soda and then removed.
The liquid is then evaporated under a vacuum of 27 to 28 in. of
mercury, and, when of specific gravity 1.295 (corresponding to about
80% of glycerin), it is distilled under a vacuum of 28 to 29 in. In
the Glatz process the lye is treated with a little milk of lime, the
liquid then neutralized with hydrochloric acid, and the liquid
filtered. Evaporation and subsequent distillation under a high vacuum
gives crude glycerin. The impure glycerin obtained as above is
purified by redistillation in steam and evaporation in vacuum pans.
_Technical Uses._--Besides its use as a starting-point in the
production of "nitroglycerin" (q.v.) and other chemical products,
glycerin is largely employed for a number of purposes in the arts, its
application thereto being due to its peculiar physical properties.
Thus its non-liability to freeze (when not absolutely anhydrous, which
it practically never is when freely exposed to the air) and its
non-volatility at ordinary temperatures, combined with its power of
always keeping fluid and not drying up and hardening, render it
valuable as a lubricating agent for clockwork, watches, &c., as a
substitute for water in wet gas-meters, and as an ingredient in
cataplasms, plasters, modelling clay, pasty colouring matters, dyeing
materials, moist colours for artists, and numerous other analogous
substances which are required to be kept in a permanently soft
condition. Glycerin acts as a preservative against decomposition,
owing to its antiseptic qualities, which also led to its being
employed to preserve untanned leather (especially during transit when
exported, the hides being, moreover, kept soft and supple); to make
solutions of gelatin, albumen, gum, paste, cements, &c. which will
keep without decomposition; to preserve meat and other edibles; to
mount anatomical preparations; to preserve vaccine lymph unchanged;
and for many similar purposes. Its solvent power is also utilized in
the production of various colouring fluids, where the colouring matter
would not dissolve in water alone; thus aniline violet, the tinctorial
constituents of madder, and various allied colouring matters dissolve
in glycerin, forming liquids which remain coloured even when diluted
with water, the colouring matters being either retained in suspension
or dissolved by the glycerin present in the diluted fluid. Glycerin is
also employed in the manufacture of formic acid (q.v.). Certain kinds
of copying inks are greatly improved by the substitution of glycerin,
in part or entirely, for the sugar or honey usually added.
In its medicinal use glycerin is an excellent solvent for such
substances as iodine, alkaloids, alkalis, &c., and is therefore used
for applying them to diseased surfaces, especially as it aids in their
absorption. It does not evaporate or turn rancid, whilst its marked
hygroscopic action ensures the moistness and softness of any surface
that it covers. Given by the mouth glycerin produces purging if large
doses are administered, and has the same action if only a small
quantity be introduced into the rectum. For this purpose it is very
largely used either as a suppository or in the fluid form (one or two
drachms). The result is prompt, safe and painless. Glycerin is useless
as a food and is not in any sense a substitute for cod-liver oil. Very
large doses in animals cause lethargy, collapse and death.
GLYCOLS, in organic chemistry, the generic name given to the aliphatic
dihydric alcohols. These compounds may be obtained by heating the
alkylen iodides or bromides (e.g. ethylene dibromide) with silver
acetate or with potassium acetate and alcohol, the esters so produced
being then hydrolysed with caustic alkalis, thus:
C2H4Br2 + 2 C2H3O2.Ag --> C2H4(O.C2H3O)2 --> C2H4(OH)2 + 2 K.C2H3O2;
by the direct union of water with the alkylen oxides; by oxidation of
the olefines with cold potassium permanganate solution (G. Wagner,
_Ber._, 1888, 21, p. 1231), or by the action of nitrous acid on the
diamines.
Glycols may be classified as _primary_, containing two -CH2OH groups;
_primary-secondary_, containing the grouping -CH(OH).CH2OH; _secondary_,
with the grouping -CH(OH).CH(OH)-; and _tertiary_, with the grouping
>C(OH).(OH)C<. The secondary glycols are prepared by the action of
alcoholic potash on aldehydes, thus: