T. E. (Thomas Edward) Thorpe.

A dictionary of applied chemistry online

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sembling them BO closely, indeed, that without
examination they may be readily mistaken for
the genuine article. They are, however, all
remarkable for their low degree of hardness, less
than that of ordinary window-glass, and they
can be readily scratched with a knife. In
course of time, they display a dark leaden
tarnish on their surface, and when worn in
jewellery their edges become rubbed and
chipped. When examined with a magnifying-
lens, bubbles and streaks are often to be seen
in them. Optically they are isotropic and
lacking in diohroism.

To avoid the effects of abrasion in wear, and
also no doubt as a deception in case the test of
hardness is applied, these soft materials are
sometimes faced with a harder material such as
rock-crystal or colourless topaz. In the doublet,
the upper portion, above the girdle, consists of
this harder, colourless material, while the lower
portion, protected in the setting, consists of
coloured strass which imparts its fine colour and
briUiancy to the whole. The triplet consists of
an upper and a lower portion of harder material,
with a layer of the coloured strass between.
Such counterfeits can, of course, be readily
detected when the unmounted gem is viewed
sideways, but when it is mounted in its setting
detection is not so easy. Doublets and triplets
are also built up of genuine stones, with the
object of improving the colour, and of pro-
ducing a gem of larger size.

Another kind of fraud sometimes practised
with precious stones is the substitution of less
valuable stones for more valuable. Unfortu-
nately, the nomenclature of gems, as adopted by
jeweUers, rather offers an opening in this direc-
tion. Thus stones of a red colour are often
known ooUeotively as ruby with some qualifying
prefix: e.g. 'spinel-ruby ' (=spinel), 'Cape
ruby' (=pyrope garnet), and 'Siberian ruby'
(=tourmaliiie), the true ruby (" Oriental ruby '
of jewellers) being, of course, corundum ; or
again, 'Oriental emerald' (=corundum), 'Ural-
ian emerald' (=demantoid garnet), ' lithia-
emerald' (=spodumene) and 'Brazilian emer-
ald' (=tourmaline), the true emerald being
beryl of a grass-green colour. In the same way,
yellow quartz (' Spanish topaz ' or ' Occidental
topaz ') is often mistaken for and sold as topaz.
.Other deceptive terms of a Uke nature are
' Marmorosch diamonds,' ' Cornish diamonds,'
' Bristol diamonds,' &c., for small sparkling
crystals of quartz ; and ' Matura diamonds '
(from Matura in Ceylon) for zircon of a brUliant



lustre, which has been decolourised by the
application of heat. The latter, as well as
colourless corundum (' white sapphire '), have
occasionally been passed off as diamonds.

Other attempts have been made to produce
gems of much the same chemical composition
as the genuine stones. Eor example, green
glass \vith the composition of emerald. Very
successful imitations of turquoise have been
obtained by submitting to pressure a precipitate
having the same composition as the natural

The artificial colouring of natural stones is
also extensively practised. Almost all cut
agates have been so treated (w. Agate). Chalce-
dony can be so cleverly coloured a delicate
green \vith salts of nickel or chromium, as to
be practically indistinguishable from the more
expensive chrysoprase. The colour of many
gem-stones can be changed by heating or by
exposure to the emanations of radium. A
trick of the meanest kind is to smear violet ink
or other bluish colouring matter on the surface
of a yellowish (' off-coloured ') diamond, so
giving it the appearance of a colourless gem.

JJe/erence.— M. Bauer, Precious Stones,
English transl. by L. J. Spencer, 1904

L. J. S.
GENISTA TINCTORIA v. Dybk's broom.
GENISTEIN V. Dyer's broom.
GENTIAN. GentianoB radix. (Racine de
Gentiane, I^. ; Enzianvmrzd, Ger.) The
dried root of the Gentiana lutea (Linn.) (Bentl.
a. Trim. 182) is used in medicine as a bitter tonic.
Its physiological activity appears to depend
upon the presence of a small proportion of a
bitter crystalline glucoside, gentiopicrin, gentian-
bitter, or gentianin, which was first obtained in a
definite form by Kromayer (Die Bitterstoffe,
Erlangen, 1861, 105 : Gm. 16, 193).

To prepare gentiopicrin, the fresh gentian
root is cut into small pieces and quickly dropped
into boiling alcohol in order to destroy the
ferment which is present in the root aud would
otherwise lead to loss of glucoside. The liquid
is boiled for 30 minutes, cooled, and filtered.
The alcohol is then removed by evaporation,
the residual Uquid mixed with calcium carbonate,
filtered, evaporated to a syrup, and allowed to
stand for a fortnight to crystallise. The crystals
obtained are purified by reorystallisation from
a mixture of equal volumes of chloroform and
95 p.o. alcohol (Bourquelot and Herissey,
Compt. rend. 131, 113). Gentiopicrin has the
composition C,„H2„Os,JHaO. It melts at 122°,
or, when anhydrous, at 191° (Tanret, ibid. 141,
207). By the action of dilute acids or emulsin,
gentiopicrin breaks up into dextrose, and flakes
of a yellow amorphous compound gentiogenin,
which is soluble in alcohol, but almost insoluble
in water.

The mother liquors resulting from the
purification of gentiopicrin contain a compound,
gentiin CjjHjsOij, which forms mioroscopio
slightly yellow needles, m.p. 274° (decomp.).
It is slowly hydrolysed by dilute sulphuric acid
at 100°, forming dextrose (1 mol.), xylose
(1 mol.), and gentienin C„H,„Or, (1 mol.). Tlie
last-named compound, on heating, begins to
sublime at 195° and melts at 225°. It is iso-
meric with gentisin, another constituent of
gentian to be described presently, but melts at a

lower temperature, and gives a yellow colouration
with nitric acid. Gentisin, under these circum-
stances, gives a green colour (Tanret, Compt.
rend. 141, 263). The alcoholic extract of
gentian root, from which gentiopicrin separates,
also contains an amorphous glucoside, gentio-
mon'ra,. which has the composition CjjHjaOio or
CijHjoOio. On hydrolysis with acids, gentio-
marin yields an amorphous brown substance ;
with emulsin, dextrose and an amorphous
maroon - coloured substance distinct from
gentiogenin (Tanret, Bull. Soo. chim. [iii.] 33,

Gentian also contains, in very small propor-
tion, another compound which, though physio-
logically inactive, is much better known. It is
a yellow crystalline acid, gentianic acid, gen-
tisin, or gentianin CijHjoOj, and by the earher
investigators (Gm. 16, 178) was confused with
gentian-bitter or gentiopicrin, and to both these
compounds the name ' gentianin' has been
applied. To obtain gentianic acid, the powdered
root, after removal of pectin and saccharine
constituents, by prolonged maceration in cold
water, is extracted with boihng alcohol. Most
of the alcohol is removed from the solution by
distillation, when on the addition of water a
precipitate forms consisting of impure gentianic
acid. This, after washing with ether, may be
purified further by recrystallisation from alcohol
or by conversion into a potassium salt, and re-
generation with acetic acid (Henry and Caven-
tou, J. Pharm. Chim. 7, 173 ; Trommsdorff,
Annalen, 21, 134 ; Leconte, ibid. 25, 202 ;
Baumert, ibid. 62, 106 ; Hlasiwetz and Haber-
mann, ibid. 175, 63 ; 180. 348).

Gentisin crystallises in large pale-yellow
silky needles. Heated to 200°, it darkens in
colour, and sublimes with decomposition at
300°-^0°. It is nearly insoluble in water, at
16°, 1 part requiring 3630 parts of water for
solution, but in alkaline solutions and in hot
alcohol it dissolves readily. Melted with potash,
acetic acid, phlorogluoin and gentisic acid

(1:2:5) are formed (H. and H.).

Gentisin has been obtained synthetically by
Kbstanecki and Tambor (Monatsh. 15, 1), and
is the methyl ether of gentisein, 1:3: 7-tri-

hydroxyxanthone 0HCjHj<^,Q^CeH2{0H)2

which compound is formed when the methyl
group is eliminated from gentisin by boiling with
hydriodic acid (Kostanecki, Monatsh. 12, 205).

Pectin is present in gentian root in large
proportion. This yields mucio acid on oxidation
by dilute nitric acid and arabinose on hydrolysis
with dilute sulphuric acid (Bourquelot and
He'rissey, J. Phaim. Chim. [vi.] 8, 49). Fer-
mentable sugar is present in so large a propor-
tion that it has led to the root being employed
in Switzerland and Bavaria in the manufacture
of spirit. Investigations carried out by Bour-
quelot and his co-workers (Bourquelot and
Nardin, Compt. rend. 126, 280 ; Bourquelot
and Herissey, ibid. 131, 750 ; 135, 290) show
that fresh gentian root contains gentianose, a
hexotriose, CjsHjjOij, which melts at 207°-209°,
and is dextro-rotatory. It does not reduce
Fehling's solution, but, if boiled mth dilute
sulphuric acid or acted upon by invertase, it
becomes laevo -rotatory, and acquires considerable



reducing power, having become hydrolysed
into IsBvulose and a new hexobiose, gentidbiose,
which, by more vigorous treatment, can be
hydrolysed into 2 molecules of dextrose.

For the detection of gentian-bitter in beer,
V. Dragendorff (Chem. Zentr. 1881, 285 and 299) ;
Allen (Analyst, 12, 107 ; 13, 43). A. S.

GENTIAN ROOT. ' The Gentiana lutea (Linn.),
from which the gentian root is derived, chiefly
occurs in mountainous districts, especially in
Switzerland and the Tyrol. There is present
in the root of this and other species of gentiana a
bitter principle which is said to possess valuable
tonic virtues, and on this account some quantity
of the material is imported into this country for
medicinal purposes.

Gentisin, the colouring matter of gentian
root, was _first isolated by Henry and Caventou
(J. Pharm. Chim. 1821, 178), and was shown by
Baumert (Annalen, 62, 106) to possess the
formula CuHjuOj. Hlasiwetz and Habermann
{ilid. 175, 63 ; 180, 343), somewhat kter, found
that gentisin contains two hydroxyl groups, and
that, when fused with potassium hydrate,
phh/rgVacinol and geniisic acid (hydroquinone
carboxylic acid) are produced from it. By the
action of hydrochloric acid on fused gentisin,
methyl chloride was evolved, a probable indica-
tion of the presence of a methoxy- group. To
prepare gentisin (Baumert, I.e.), the root is well
washed with water, then extracted with alcohol,
and the extract evaporated to a small bulk. The
residue is washed with water to remove the
bitter principle, and then with ether to extract
plant wax. For purification, the crude colouring
matter is repeatedly crystallised from alcohol :
10 kUos. of the root yield about 4 grams of the
substance. Gentisin crystallises in yellow
needles, is sparingly soluble in alcohol, and dis-
solved in alkaline solutions wdth a yellow colour.

Gentisein C,3H,Os,2H20. When gentisin is
digested with boihng hydriodio acid, it is con-
verted into gentisein with evolution of 1 molecule
of methyl iodide. Gentisein consists of straw-
yellow needles, melting at 315°, and gives with
sodium amalgam a blood - red colouration,
whereas gentisin, by a similar method, yields a
deep green-coloured liquid (Kostaneoki, Monatsh.
12, 205). By the action of acetic anhydride,
gentisein is converted into a triacetyl derivative,
Ci3H505(C2H30)3, needles, m.p. 226° (Kos-
tanecki. I.e.); but on methylation with methyl
iodide, a dimethyl ether Cj3Hr.02(OH)(OCH3)2,
yellow needles, m.p. 167°, is produced (Kosta-
neoki and Schmidt, Monatsh. 12, 318).

Partial methylation converts gentisein into
gentisin, and it is thus certain that the latter
consists of gentisein monomethyl ether. Kosta-
neoki and Tambor (Monatsh. 15, 1) obtained
gentisein by distiUing a mixture of phloro-
glucinol and hydroquinone carboxylic acid with
acetic anhydride

/x OH- , V OH

ohL Jcooh ^ '\ /'


I? I




and its constitution is therefore represented as
1 :3:7-trihydroxy-xanthone. Bya study of dia-
azdbenzene-gentiain, C^^fifJifi^'B.^^,^, scarlet-
red needles, m.p. 251°-252° (Perkin, Chem. Soo.
Trans. 73, 1028), which gives the diacetyl deri-
vative, C,iH,05(C2H30)2(CeHsN2)2, orange-red
needles, m.p. 218°-220°, it has been shown that
gentisin itself possesses the constitution I.

^x ^0^ /x



/ \/

■^ co-








As gentisin yields by means of methyl iodide
only a monomethyl ether, the original methoxy-

froup cannot be in the position ( 1 ). On the other
and, if gentisin ie represented by the formula II.,
the azobenzene groups would enter the positions
4 and 2, and from such a compound an acetyl-
derivative cannot be obtained (compare dis-
azobenzene phloroglucinol).

Gentisin is a feeble dyestuff, and gives on
wool mordanted vrith chromium, aluminium,
and tin respectively, pale-green yellow, pale
bright yellow, and very pale cream-coloured
shades (Perkin and Hummel, Chem. Soc. Trans.
1896, 69, 1290). A. G. P.


GENTIAN BLUE 6 B. Spirit Soltihle Blue,
Spirit Blue O, Opal Blue v. Teiphenylmethane


GENTIANOSE v. Caebohydratbs.
GENTIIN V. Glucosides.
GENTIOPICRIN v. Gentian; also Gluco-



Gentian and Proto-

oatechuic acid.

GENTISIN V. Gentian boot and Gentian.

GEOSOTE V. Synthetic drugs.

GERANINE v. Azo- coloueing^ matters
and Pkimuline.

GERANIUM OIL v. Oils, Essential.

GERMANIUM, Ge. At. wt. 72-5 (Winkler), is
the ekasilicon predicted by Mendelceff. It was
discovered by Winkler in 1866 in argyrodite
GeS2,4Ag2S, in which it is present to the extent
of about 6-7 p.c. (Kolbeck, Centr. Min. 1908,
331). It is also present in canfieldite, franckeite,
and brongniardite (Prior and Spencer, Min. JM ag.
1898, 12, 5 ; Shroutsohoff, J. Russ. Phys. Chem.
Soc. 1892, 130), but its presence in euxenite and
samarakite has been denied by Lincio (Centr.
Min. 1904, 142). The metal is obtained by the
reduction of the dioxide with carbon at a red
heat. It is a greyish-white, brittle, readily
powdered lustrous metal of sp.gr. 5-469, wiiich
melts at 500°, and does not volatilise at 1350°.
It oxidises in air at high temperatures, combines
directly with the halogtas, is insoluble in hydro-
chloric acid, and dissolves in aqua regia, forming
the dioxide.

Compounds. — The metal is tetravalent, and its
compounds resemble those of the silicon group.

Germanium dioxide GeOj is obtained from
argyrodite by treating the latter with nitre and



potasaium carbonate at a red heat, then with
acid, after which it is purified by being con-
verted into the sulphide, which is roasted and
treated with nitric acid. The oxide forms a
white powder having acid properties, but
soluble in acids, and is readily reduced by carbon,
sodium or magnesium. A colloidal solution of
germanium hydroxide is obtained by decom-
posing an alkaline solution of the dioxide with
carbon dioxide.

Qermanous oxide, GeO is a greyish - black
powder, and the corresponding hydroxide
Ge(0H)2 is a yeUow powder obtained by the
action of alkalis on germanium chloroform or
chloride. According to Hantzsch (Zeitsch.
anorg. Chem. 1902, 30, 289), in aqueous solution
it is a weak monobasic acid, and has the con-
stitution HGeO'OH, being analogous to formic

Germanium chloroform GeHClj is obtained
when germanium is heated in a current of
hydrogen chloride, a colourless liquid being thus
formed, which separates into two layers, of which
the heavier is germanium chloroform ; it is a
colourless fuming Uquid, b.pL 75°. The lighter
liquid is germanium oxychlorule, GeOCla ; it is
similar in properties to the ^lo^oform, but is
less mobile, and boils above U)0°. Germanium
dichloride GeClj, the tetrachlmde GeClj, and
the corresponding tetrabromide,\ -iodide, and
-ethide GeEtj, are also known.

Germanium tetrafiuoride GeFjjSHjO com-
bines with hydrofluoric acid, forming germano-
fluoric acid, of which the potassium salt K^GeF^
forms hexagonal crystals isomorphous with
those of ammonium silioofluoride.

Germanium disulphide GeS^ is the most
ohaxaoteristio of the germanium derivatives, and
is prepared by passing sulphuretted hydrogen
in a solution of germanium dioxide ; it is a
white powder, soluble in water to some extent
and in ammonium sulphide (Vogelen, Zeitsch.
anorg. Chem. 1902, 30, 329). The monosul-
phide GeS and thiogermanates are also known
(J. pr. Chem. 1887, [2] 36, 177 ; Ber. 1888, 21,

Germanium hydride GeHj is formed when
germanium chloride is reduced with sodium
amalgam. It is also formed as a mirror in the
Marsh apparatus, as in the arsenic test. Thp-
mirror is red by transmitted and green by reflepted
light, is soluble in sodium hypochlorite; but
with difficulty in hot hydrochloric acid.' With
sulphuretted hydrogen it forms the sulphide ;
heated in air it gives the dioxide, whilst with
silver nitralte it forms a black silver germanium
compound, probably GeAgj (Vogelen, I.e. 325).

GERMOL. A disinfectant consisting of
crude cresols.

GESILIT V. Explosives.

GETAH WAX v. Waxes.


GHEE. A clarified butter used in the East
mainly for cooking.



GIANT POWDER v. Explosives.

names for Tinospora cordifolia (Miers). This
plant flourishes in India, the drug being sold
extensively in the bazaars as a tonic and anti-
periodic, in the form of cylindrical pieces, 2 to

6 cm. long and 1 to 5 cm. in diameter. It is a
perennial creeper, climbing to the summit of the
highest trees, its branches putting forth roots
which, reaching to the ground, initiate a fresh
growth. Roots, stem, and leaves are equally
in demand as a drug. The Indian pharmacopoeia
commends its use as a tincture (4 to 8 c.c. in
die) ; as an extract (0-6 gram to 1 gram per diem
in the form of piUs) ; and as an infusion (1 : 10),
of which 60 c.c. to 90 c.c. are to be taken thrice
a day. The stems contain verberin, an un-
crystaUisable bitter substance, changed by
dilute sulphuric acid into a gluooside, and a
bitter kind of starch meal Imown as ' palo '
(J. Soc. Chem. Ind. 6, 49).

GIN or GENEVA is a spirituous liquor made
from spirit derived from grain and distilled with
juniper berries and other flavouring substances.
The term is a corruption of the word ' geniiwe '
or ' junever,' the lYench and Dutch equivalents
respectively for juniper, which is the essential
flavouring ingredient.

The principal varieties are the English,
known as ' gin,' and the Dutch, described as
'Geneva,' 'Hollands,' and 'Schnapps.' The
difference between them is chiefly one of flavour,
and each manufacturer ha.s his own special
recipe, which is carefully preserved as a trade
secret. The principal flavouring ingredients
used besides juniper are angelica root, almond
cake, calamus root, cardamom seeds, cassia
buds, coriander seeds, creosote, liquorice powder,
orris root, sweet fennel, turpentine, &c.

The grain used is almost invariably a mixture
of maize, malt, and rye, the proportions being
usually about 75 p.o. maize, 15 p.c. malt, and
10 p.c. rye for English gin, and about equal parts
of each for the Dutch varieties, although some-
times maize is absent.

During the Napoleonic wars at the beginning
of the last century, the use of com, owing to its
scarcity, was prohibited in the United Kingdom
for the manufacture of spirit, and the manu-
facturers had recourse to molasses or low-grade
sugar. This, however, produces a very inferior
quality of gin, which is essentially a grain spirit,
but it is stm made, chiefly for exportation, by
the addition of juniper oil or similar flavouring
agent to the crude spirit.

In England, patent-still spirit is generally
employed as a basis, but it is preferably not
rectified so highly as to deprive it of the charac-
teristic flavour of grain spirit. The flavouring
ingredients are in some cases added directly or
they are separately distilled and the distillate
added to the spirit to be flavoured. Another
and probably the best method is to redistil the
spirit, after the addition of the flavouring
ingredients, in a kind of pot-stUl with a long head
or other simple rectifying arrangement.

In Holland, the manufacture is carried on
mainly at Schiedam, where pot-stills are chiefly
employed. The spirit is subjected to three or
four rectifications, when it is known as ' mout-
wijn' or ' maltwine.' This is sold to the manu-
facturers of Geneva or !^oUands who flavour it
by methods similar to those above described for
English gin.

The best ' Hollands ' is said to be prepared
as follows : A mixture of two measures of ground
rye with one measure of ground barley malt is
mashed with about 24 gallons of water for each



owt. of the mixed meal. The mashing being
completed, the sp.gr. of the wort is reduced by
cold water to between 1033 and 1038. It is
then fermented, after which the whole is thrown
into a stUl. To the first product of distillation,
called low mnes, a varying proportion of juniper
berries with a little salt is added, and it is re-
distilled. The spirit which now passes over is
flavoured with essential oils or resins derived
from the juniper as well as from the rye and
barley used in brewing.

Sweetened gin (e.g. ' Old Tom' and ' Old
Geneva ') is made by the addition of sugar
syrup to plain gin. The syrup is prepared by
dissolving refined sugar in its own weight of
pure water. Sometimes it is flavoured with
orange-flower water, and is known as ' oapillaire.'
The clear solution is added in the proportion of
about 6 gallons of syrup to 100 gallons of gin.

Plymouth gin is a special variety of gin made
in Plymouth, and used extensively in the West
of England. It has a characteristic flavour, said
to be due to ether resulting from the addition of
a little sulphuric acid to the spirit to be rectified.

The adulteration of gin, except by dilution
with" water, is not common. Alkaline car-
bonates, and sometimes alum and salts of zinc
and lead, have been found. Jtmiper wood oil
and turpentine oil are occasionally used as sub-
stitutes for or admixed with the oil from the
juniper berry.

By the Sale of Food and Drugs Amendment
Act, 42 & 43 Vict. c. 30, s. 6, gin may not be
sold at a strength below 35 under proof, unless
declared to be diluted. The percentage of
water added may be found by multiplying the
excess of degrees under proof beyond 35 by the
factor 1'54. Eor example, a gin of strength
45 u.p. contains 10x1 -64, or 15-4 p.c. of added
water over and above that present in gin at the
minimum statutory strength of 35 u.p.


Description. — Ginger is the dried rhizome,
either whole or ground to a powder, of Zingiber
officinale (Roscoe), a plant 3 to 4 feet in height,
which grows wild in India and China and is
' cultivated extensively in most tropical countries.
At the present time, the chief kinds which find
their way into the English market are Jamaica,
Calicut, Cochin, African, Japanese, and in less
quantity, Bombay. Japanese ginger is not

derived from Z. officinalis and is therefore not
official for medicinal purposes.

Preparation and properties. — ^The rhizomes
are dug up when the plant is about a year old,
washed, and dried in the sun. In some cases
the epidermis is removed by scraping or cutting,
in others the root is dried intact.

To meet the popular prejudice in favour of a
white product various methods of treating the
root are adopted. The commonest consists in
immersion in mUk of lime, when the coating of
lime left after drying is of advantage in pre-
venting the attacks of insects, fungi, &c.
Gypsum and chalk are also used with a similar
object. Ginger is also said to be bleached with
sulphurous acid or bleaching powder, but most
of the so-called bleached ginger has probably
only been ' limed.'

The unsoraped root has a yellow-brown
wrinkled surface, while the scraped variety is
smooth and nearly white. The pieces are, as a
rule, from 2 to 4 inches in length, knotted and
bent, flattened in section and with a short

On being cut with a, knife, the best ginger
presents a soft floury surface, inferior qualities
appear hard, resinous, and shiny.

The chief structures observed when ground
ginger is examined under the microscope are the
starch grains, the vessels, reticulated, spiral, and
scalariform, the sclerenchymatous ceUs, broad
bast fibres with somewhat thin walls and

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