ALBATA See German Silver.
AMALGAMS Mercury and other metals.
BATH-METAL Copper and zinc.
BELL-METAL Copper and tin.
BRASS Copper and zinc.
BRITANNIA METAL Tin with antimony, copper, and bismuth.
BRONZE Tin and copper.
BRONZE ALUMINIUM Copper and aluminium.
CANNON-METAL Tin and copper.
DUTCH GOLD Copper and zinc.
FUSIBLE METAL Bismuth, lead, and tin.
GERMAN SILVER Copper, nickel, and zinc, with,
sometimes, a little iron and tin.
GOLD (_standard_) Gold with copper.
GOLD (_old standard_) Gold with copper and silver.
GUN-METAL See Cannon-metal.
MOSAIC GOLD Copper and zinc.
OR-MOLU Copper and zinc.
PEWTER (_common_) Tin and lead.
PEWTER (_best_) Tin with antimony, bismuth and copper.
POT-METAL, COCK-METAL Copper and lead, with,
sometimes, a little zinc.
QUEEN'S METAL Tin with antimony, bismuth, and copper.
SHOT-METAL Lead with a little arsenic.
SILVER (_standard_) Silver and copper.
SOLDER Tin and lead.
SPECULUM-METAL Tin and copper, and arsenic.
STEREOTYPE-METAL Lead, antimony, and bismuth.
TOMBAC, RED TOMBAC Copper and zinc.
TUTANIA See Britannia metal.
TYPE-METAL Lead and antimony.
WHITE COPPER (_Packfong_; Copper and arsenic.
_Whitetombac_)
[Footnote 27: For the proportions of the component metals, refer to the
alloys under their respective heads.]
_Prop., &c._ Alloys generally possess characteristics unshared by their
component metals. Thus, copper and zinc form brass, which has a different
density, hardness, and colour to either of its constituents. Whether the
metals tend to unite in atomic proportions, or in any definite ratio, is
still undetermined. The evidence afforded by the natural alloys of gold
and silver, and by the phenomena accompanying the cooling of several
alloys from the state of fusion, goes far to prove that such is the case.
(Rudberg.) The subject is, however, one of considerable difficulty, as
metals and metallic compounds are generally soluble in each other, and
unite by a simple fusion and contact. That they do not combine
indifferently with each other, but exercise a species of elective affinity
not dissimilar to other bodies, is clearly shown by the homogeneity and
superior quality of many alloys in which the constituent metals are in
atomic proportions. The variation of the specific gravity and
melting-points of alloys from the mean of those of their component metals,
also affords strong evidence of a chemical change having taken place.
Thus, alloys generally melt at lower temperatures than those required for
their separate metals. They also usually possess more tenacity and
hardness than the mean of their constituents.
Matthiessen found that when weights are suspend to spirals of hard-drawn
wire made of copper, silver, gold, or platinum, they become nearly
straightened when stretched by a moderate weight; but wires of equal
dimensions composed of copper-tin (12% of tin), silver-platinum (36% of
platinum), and gold-copper (84% of copper), scarcely undergo any permanent
change in form when subjected to tension by the same weight.
The same chemist gives the following approximative results upon the
tenacity of certain metals and wires hard drawn through the same gauge
(No. 23):
Breaking strain for:
lbs.
Copper 25-30
Tin under 7
Lead " 7
Tin-lead (20% lead) about 7
Tin-copper (12% copper) " 7
Copper-tin (12% tin) " 80-90
Gold 20-25
Gold-copper (8·4% copper) 70-75
Silver 45-50
Platinum 45-50
Silver-platinum (30% platinum) 75-80
On the other hand, their malleability, ductility, and power of resisting
oxygen is generally diminished. The alloy formed of two brittle metals is
always brittle; that of a brittle and a ductile metal, generally so; and
even two ductile metals sometimes unite to form a brittle compound. The
alloys formed of metals having different fusing-points are usually
malleable whilst cold, and brittle whilst hot. The action of the air on
alloys is generally less than on their simple metals, unless the former
are heated. A mixture of 1 part of tin and 3 parts of lead is scarcely
acted on at common temperatures; but at a red heat it readily takes fire,
and continues to burn for some time like a piece of bad turf. In like
manner, a mixture of tin and zinc, when strongly heated, decomposes both
moist air and steam with almost fearful rapidity.
The specific gravity of alloys is never the arithmetical mean of that of
their constituents, as commonly taught; and in many cases considerable
condensation or expansion occurs. When there is a strong affinity between
two metals, the density of their alloy is generally greater than the
calculated mean; and _vice versâ_, as may be seen in the following
Table:--
_Alloys having a density_--
Greater than the mean of Less than the mean
their constituents:-- of their constituents:--
Copper and bismuth, Gold and copper,
" palladium, " iridium,
" tin, " iron,
" zinc, " lead,
Gold and antimony, " nickel,
" bismuth, " silver,
" cobalt, Iron and antimony,
" tin, " bismuth,
" zinc, " lead,
Lead and antimony, Nickel and arsenic,
Palladium and bismuth, Silver and copper,
Platinum and molybdenum, Tin and antimony,
Silver and antimony, " lead,
" bismuth, " palladium,
" lead, Zinc and antimony.
" tin,
" zinc.
"Every alloy," says Dr Ure, "is, in reference to the arts and
manufactures, a new metal, on account of its chemical and physical
properties. A vast field here remains to be explored. Not above sixty
alloys have been studied by chemists, out of many hundreds which may be
made, and of these very few have yet been practically employed. Very
slight modifications often constitute very valuable improvements upon
metallic bodies." See ANALYSIS, ASSAYING, BRASS, BRONZE, ELECTROTYPE,
GERMAN SILVER, GOLD, METALS, SPECIFIC GRAVITY, &c.
=ALL'SPICE.= See PIMENTO.
=ALLU''VIAL.= (-l'[=o][=o]v'-y[)a]l). _Syn._ ALLU''VIOUS*; ALLU''VIUS, L.;
D'ALLUVION, Fr. In _geology_, applied to partial deposits of mud, sand,
gravel, &c., left by rivers and floods upon land not permanently submerged
beneath water; in _agriculture_, applied to soils so formed or deposited.
=ALLU''VIUM.= [L., Eng.] _Syn._ ALLUVION, Fr.; ANFLÖSSUNG, ANSCHWEMMUNG,
Ger. In _geol._ and _agr._, alluvial deposit or soil. See SOILS, &c.
=AL'LYL= (-l[)i]l). C_{3}H_{5}. In _chemistry_, the radical of the
essential oils containing sulphur, as those of assaf[oe]tida, garlic,
horseradish, mustard, onions, &c., which are either sulphides or
sulphocyanides of allyl. Its probable existence was first shown by Captain
Reynolds, who succeeded in producing several of its derivatives. It has
since been obtained, in a separate state, by the action of sodium upon
iodide of allyl. It is an oily substance with a high boiling point.
=Allyl, Sulphide of=, (C_{3}H_{5})_{2}S; obtained (artificially) by acting
on sulphocyanide of allyl with sulphide of potassium. See OIL OF GARLICK.
=Allyl, Sulphocy'anide of=, C_{3}H_{5}CNS; obtained by submitting iodide
of allyl to the action of sulphocyanide of potassium; or by gently heating
a mixed alcoholic solution of sulphide of allyl and bichloride of mercury,
with sulphocyanide of potassium. See OIL OF MUSTARD (VOLATILE).
=AL'MOND= (ah'-m[)u]nd). _Syn._ AMYG'DALA (also -US, -UM*), L.; AMANDE,
Fr.; MANDEL, Ger., Dut., Dan., Swed. The 'almond-tree' (_amyg'dalus
commu'nis_--Linn.; Ph. L., E., and D.; _Amandier_--Fr.), a tree of the
nat. ord. Rosaceæ, indigenous to Persia, Syria, and the north of Africa;
but also extensively cultivated in southern Europe. The almond-tree is
about the size of the peach-tree, which it much resembles in appearance.
It is incapable of ripening its fruit in this country, and is, therefore,
only grown here for the sake of its beautiful vernal flowers. There are
several varieties, of which the most important are the sweet and the
bitter, so named from the flavour of the seed or kernel. These, for the
most part, resemble each other in appearance. De Candolle ('Prodromus,'
ii, 530) gives five varieties of this species:--A. AMA''RA
(_bitter-almond_); A. DUL'CIS (_sweet-a._); A. FRAGILIS (_tender-shelled
a._); A. MACROCAR'PA (_large-fruited a._, _pista'chio a._, _sultana a._);
A. PERSICO'ÏDES (_peach a._).
=Almond, Per'sian.= The peach.
=AL'MONDS=. _Syn._ AMYG'DALÆ, L.; AMANDES, Fr.; MANDELN, Ger. The seed or
kernels of the almond-tree. They are met with in commerce both in the
shell (AMYG'DALÆ CUM PUTAM'INE, -[)i]n-e, L.), and shelled (AMYGDALÆ, L.).
In the retail shops, most commonly in the latter form. Those rancid,
broken, or worm-eaten should be rejected.
=Almonds, Bitt'er.= _Syn._ AMYG'DALÆ AMA''RÆ, L.; AMYGDALA AMARA, Ph. E.;
AMANDES AMÈRES, Fr.; BITTERE MANDELN, Ger. A variety imported from
Mogadore, chiefly characterised by possessing the bitter flavour, and when
rubbed with water, the odour of peach-kernels. They are also smaller and
thicker than the sweet almond.
_Uses, &c._ Bitter almonds are used to relieve the flavour of sweet
almonds, to clear muddy water, and to flavour confectionery, liqueurs, &c.
By pressure, they yield their bland oil (OIL OF ALMONDS; O'LEUM AMYG'DALÆ,
L.); the resulting cake (BITTER-A. CAKE; PLACEN'TA A. AMARÆ, L.) is
distilled for the volatile oil (ESSENTIAL OIL OF A.; O. A. A., L.), and is
afterwards again pressed into cakes (A.-CAKE), and used to fatten pigs,
and for other purposes. Bitter almonds are now seldom employed in
medicines, although it is said that they have cured 'intermittents' when
bark had failed (Bergius), and that their emulsion has been found useful
in pulmonary and dyspeptic affections, hooping-cough, and asthma; and
externally as a lotion in acne. (Thomson.) In large quantities they are
poisonous, and even in the smallest quantities have been known to produce
nettle-rash (_urticaria_) and other unpleasant symptoms. They have long
been in repute as an antidote to intoxication. The ancient bacchanals
chewed them at their orgies, to lessen the effects of wine, and to enable
them to take it in larger quantities with impunity.
=Almonds, Blanched'= (bl[)a]ncht'-). _Syn._ AMYG'DALÆ DECORTICA'TÆ, L.
Almonds from which the husk or seed-coat has been removed. This is
effected by soaking them for a short time in warm water, until the skin
can be easily removed by pressure between the thumb and forefinger. They
are then peeled, rinsed in cold water, drained, and dried. When intended
for the table, the last is effected by wiping them with a soft towel; but
when they are intended to be powdered, or kept, they are dried by a very
gentle heat in a stove, or in the sun.
=Almonds, Burnt'.= _Syn._ ROASTED ALMONDS; ALMOND COFFEE. Used to colour
and flavour liqueurs and confectionery; and formerly, as a substitute for
coffee.
=Almonds, Guia'na.= (g_h_e-[=a]_h_'-n[)a]; _g_ hard). Brazil-nuts.
=Al'monds, In'dian.= The fruit of _terminalia catappa_ (Linn.). They are
oleaginous, and nutritious; and are used as a substitute for almonds.
=Almonds, Ja'va= (j[=a]_h_'-). The nuts or kernels of _canarium commune_
(Linn.). They are eaten, made into bread, and pressed for their oil.
=Almonds, Sweet'.= _Syn._ ALMONDS; AMYG'DALÆ, L.; A. DULCES, Ph. D.;
AMYGDALA, A. JORDAN'ICA, Ph. L.; A. DULCIS, Ph. E., & Ph. L. 1836;
AMANDES, AMANDES DOUCES, Fr.; SÜSSE MANDELN, Ger. These are the well-known
dessert or table fruit of the name, and are the kind always referred to
when 'almonds' (simply) are spoken of or ordered.
_Comm. var._--1. JOR'DAN ALMONDS, which are the finest, and are imported
from Malaga. Of these there are two kinds; the one, above an inch in
length, flat, and with a clear brown cuticle, sweet, mucilaginous, and
rather tough; the other, more plump, and pointed at one end, brittle, but
equally sweet with the former.--2. VALEN'TIA A. (which come next in
quality) are about 3/8ths of an inch broad, not quite an inch long, round
at one end, and obtusely pointed at the other, flat, of a dingy brown
colour, with a dusty cuticle.--3. BAR'BARY and ITAL'IAN A., which resemble
the latter, but are generally smaller and less flattened.--4. A variety,
of medium quality, imported in baskets from Spain.
_Uses, &c._ Sweet almonds are nutritive, emollient, and demulcent; but
frequently disagree with weak stomachs. The husk is apt to occasion
indigestion and nausea. Owing to a peculiar idiosyncrasy of some habits,
dyspepsia, diarrh[oe]a, [oe]dematous swelling of the face, and urticaria
(_nettle-rash_), sometimes, though seldom, follow the use of unblanched
almonds. Blanched almonds do not produce these inconveniences, and,
therefore, should be preferred for the table. In _medicine_, almonds are
employed chiefly under the form of emulsion, confection, &c., and to
suspend oily substances in water. Their uses for dietetical purposes are
well known. Preparations of them are also employed as cosmetics. The cake
left after expressing the oil (ALMOND-CAKE) is used for washing the skin,
which it is said to render beautifully soft and clear. See ALMOND PASTE,
&c.
=AL'NIGHT=[dagger] (awl'-). A cake of wax with a wick in the midst. The
forerunner of, and a rude form of the modern dumpy night-lights called
MORTARS.
=AL'OE= ([)a]l'-o). _Syn._ AL'OË (-o-[=e]), L., Fr. (or ALOÈS), Ger.,
Ital., Sp., Belg., Dan., Dut., Swed. The aloe-tree. In _botany_, a genus
of plants of the nat. ord. Liliaceæ (DC). The species, of which there are
several, are succulent plants or small trees with endogenous stems, and
stiff, fleshy, hard, pointed leaves, abounding in a purgative principle
(ALOES), which is obtained from them by either evaporating the expressed
juice or the decoction. They are all natives of warm climates, and most of
them are indigenous to southern Africa.
_Hist._ [Hebrew: a-ènx], _aehleem_ (aloe-trees), were known to the sacred
historians; and both the plant and the inspissated juice are described by
Dioscorides[28] and Pliny.[29]
[Footnote 28: Lib. iii, c. xxv.]
[Footnote 29: 'Hist. Nat.,' lib. xxvii, c. v.]
_Uses, &c._ In Africa, the leaves of the Guinea aloe are made into ropes,
fishing-lines, bow-strings, stockings, hammocks, &c. The leaves of another
species are used to catch and hold rain-water. The expressed juice and
decoction are also used by the natives as a distaff. (Vide _infrà_.)
Comparative trials, made in Paris, of the strength of cordage and cables
formed of hemp, and of the aloe from Algiers, are said to have shown the
great superiority of the latter. Fabroni obtained a fine violet colour
from the recent juice of the aloe, which has been proposed as a dye for
silk.[30]
[Footnote 30: 'Annales de Chimie,' xxv, 305.]
=American Aloe.= The _agave Americana_ (Linn.) is a plant unconnected with
the preceding, and belonging to the nat. ord. Bromeliaceæ. It is found in
all parts of tropical America, and is largely cultivated on the shores of
the Mediterranean; and less frequently, as an exotic plant in this
country. It grows to the height of about 20 feet, and takes many years to
produce its gigantic and magnificent pyramid of flowers; shortly after
which it perishes, exhausted, as it were, by its efforts in bestowing its
rare beauty on the floral world. The vulgar belief is that it blossoms
only once in a century; but, as stated by the late Mr Loudon, it flowers
sooner or later according to the culture bestowed on it. Its sap yields a
kind of honey (AGAVE HONEY), and by fermentation an intoxicating liquor
(PULQUE); desiccated juice, mixed with wood ashes, is used as soap, and
lathers either with sea or fresh water; leaf-fibre, used as hemp to make
thread and twine.
=AL'OE-RESIN.= _Syn._ RESI'NA AL'OËS, L. The resinous matter deposited by
a decoction of aloes as it cools.
_Prep._ (Ph. L. 1746.) Boil aloes, 1 part, in water, 8 parts, and allow
the decoction, strained whilst hot, to repose until the next day; then
wash the deposited RESIN, and dry it by a gentle heat. It is probably a
mixture of aloine and oxidised extractive.
=AL'OES= (-[=o]ze). _Syn._ BITT'ER ALOES[double-dagger]; AL'OË (-o-[=e]),
L.; ALOÈS, SUC D'ALOÈS, Fr.; ALOE, GLAUSINDE ALOE, Ger.[31] The
inspissated juice or extract of several species of aloe.
[Footnote 31: Also see ALOE, (above).]
_Comp., Prep., &c._ Aloes is a complex resinous substance containing a
body called aloin, which is its active or purgative principle. It is
completely soluble in boiling water, and in alcohol or rectified spirit.
The decoction deposits an impure resin or resinoid on cooling.
_Phys. eff., Uses, &c._ Aloes is a warm stimulating purgative, in doses of
3 to 10 gr.; whilst even 1 or 2 gr. seldom fail to produce one motion
without pain or inconvenience. It is considered highly serviceable in
hypochondriacal, hysterical, and dyspeptic affections, particularly in
phlegmatic habits, and in cases arising from deficiency of bile. As an
emmenagogue, and a vermifuge, few medicines are more valuable. It acts on
the large intestines, and principally on the rectum; and, therefore,
should be administered with caution, or only in small doses, where there
is a tendency to prolapsus or piles, and in cases where uterine stimulants
(as in pregnancy, &c.) would be improper. "It is remarkable with regard to
it, that it operates almost to as good a purpose in a small as in a large
dose; and one or two grains will produce one considerable dejection, and
twenty grains will do no more, except it be that in the last dose (case)
the operation will be attended with griping, &c. It is one of the best
cures for habitual costiveness." (Cullen.) Many of the effects complained
of arise from its slow solubility in the primæ viæ, and may be obviated by
administering it in a liquid form, or in a solid form combined with soap,
which renders it freely soluble in the juices of the stomach.
Aloes is more frequently taken than, perhaps, any known purgative. It
enters into the composition of a majority of the aperient medicines
prescribed by the faculty, and forms the principal ingredient of nearly
all the advertised purgative, antibilious, and universal pills of the
nostrum-mongers. The fact of aloetic pills not acting until about 8 to 10
hours after being swallowed--so that if taken on retiring to rest at night
they do not generally disturb the patient before the usual time of rising
in the morning--has contributed more than anything else to make such
remedies popular with parties whose habits or business avocations would be
otherwise interfered with.
Aloes is also extensively used in veterinary practice. It is the most
valuable and reliable purgative for the horse of the whole materia medica;
but is less to be depended on for cattle, sheep, and hogs. Barbadoes aloes
is the best for this purpose. Cape aloes are, however, often employed,
when 1-4th more must be given.--_Dose_ (of the former), for a HORSE, 4 to
8 dr.;[32]--CATTLE, 3 to 6 dr. (followed by a purging drench);--HOGS, 5 to
15 gr.;--SHEEP, 15 to 30 gr.;[33]--DOGS (small ones), 10 to 30 gr.,
(middle-sized) 20 to 44, or even 60 gr., (large) 3/4 to 1 dr., or even 2
dr.
[Footnote 32: Aloes takes from 18 to 30, or even 36 hours, to operate on a
horse.]
[Footnote 33: Aloes, however large the dose, often fails to purge sheep.
In very large quantities it is poisonous to them.]
Aloes is also used in dyeing; and as a colouring matter in stains,
lacquers, and varnishes. Aloes, and several of its preparations, are
likewise extensively employed to adulterate porter.
_Var._ These, arranged in the order of their reputed medicinal value,
are--Socotrine, Hepatic, Barbadoes, Cape, &c.; and alphabetically, as
given below:--
=Aloes, Barba'does.= _Syn._ ALOES IN GOURDS; AL'OË BARBADEN'SIS, L., Ph.
L. & E. Imported from Barbadoes and Jamaica, usually in gourds; sometimes
in boxes. The best is the inspissated juice of the cut leaf of _aloë
vulga''ris_; an inferior quality is prepared from the decoction.--_Char.,
&c._ Opaque, lustreless, of a liver colour, a little tending to black,
with a bitter nauseous taste, and a very disagreeable odour, especially
when breathed on; powder a dull olive-yellow. It is the 'hepatic' aloes of
most continental writers, and said to be the [Greek: Aloê] of Dioscorides.
It is more active than the other varieties of aloes; but is also more apt
to occasion hæmorrhoids, and to gripe, than any of them.
=Aloes, Cab'alline= (-l[=i]ne.) _Syn._ F[OE]T'ID ALOES, HORSE A.; ALOË
CABALLI'NA, A. GUINIEN'SIS, L.; ALOÈS CABALLIN, Fr. From _aloë In'dica_
(O'Shaughnessy); or from _aloë spica'ta_ by long and careful boiling.
(Lindley.) Used only by farriers. Scarcely known in English commerce.
=Aloes, Cape.= _Syn._ ALOË CAPEN'SIS, A. LU'CIDA (_Geiger_), L. Imported
from the Cape of Good Hope, and obtained from _aloë spica'ta_, and other
Cape species. Odour stronger and even more disagreeable than that of
Barbadoes aloes; colour deep greenish-brown; appearance shining and
resinous; fracture generally glassy; powder a lively greenish-yellow;
almost completely soluble in boiling water, decoction paler than that of
other kinds. It is weaker than Barbadoes or even hepatic aloes, and is
more apt to gripe, &c., than the latter. A finer kind, known as
'_Bethelsdorp aloes_,' imported from Algoa Bay, is more of a liver colour,
and softer than the preceding, and hence often called CAPE HEPATIC-ALOES.
=Aloes, Hepat'ic.= _Syn._ BOMBAY' ALOES*, EAST-INDIA A.*, LIVER-COLOURED
SOCOTRINE A.*; ALOË HEPAT'ICA, Ph. L. & D.; A. IN'DICA, Ph. E. Imported
from Bombay and Madras. It is usually said to be obtained from "uncertain
species of aloes;" but it is almost certain that it is "the juice of the
Socotrine aloes plant which has been solidified without the aid of
artificial heat."[34]--_Char., &c._ "Opaque, of a liver colour, bitter
taste, and an unpleasant odour." (Ph. L.) It is less odorous, darker
coloured, and more opaque than Socotrine aloes; its powder has also a
duller colour, and weak spirit leaves much undissolved matter. Its
decoction on cooling frequently deposits a yellow powder. The finer and
brighter varieties of hepatic aloes are commonly sold for 'Socotrines,'
and their medicinal virtues are nearly similar. (See _below._)
[Footnote 34: Pereira, 'Elem. Mat. Med. and Therap.,' vol. ii, 188, 4th
Ed.; 'Pharm. Journ.,' vol. xi.]
=Aloes, In'dian= (various);--1. Deep brown or black, very opaque, and less
soluble than ordinary aloes. Scarcely known in commerce.--2. Several
varieties ranging in character from 'Cape aloes' to 'hepatics,' and
occasionally to 'Barbadoes,' obtained from several species.
=Aloes, Mo'cha= (-k[)a]h). _Syn._ ALOË DE MOCHÂ, L. Imported from Muscat.
An inferior kind of Indian aloes. (Christison.) It is obtained from the
same plant as produces genuine hepatic aloes. (Lindley.) It holds an
intermediate position between 'Cape' and 'hepatics,' but contains much
impurity; the latter often amounting to upwards of 25%. Some specimens
are, however, of excellent quality. When melted and 'doctored,' it is sold
for Barbadoes, hepatic, and even Socotrine aloes.
=Aloes, Soc'otrine= (-tr[)i]n; s[)u]k'-[double-dagger]). _Syn._
SOC'OTORINE ALOES, SMYR'NA A., TUR'KEY A.; ALOË SOCOTRI'NA, Ph. L.; ALOË,
Ph. L. 1836; A. SOCOTRI'NA, Ph. E. "The juice of the cut leaf of uncertain
species hardened by the air." (Ph. L.) Genuine Socotrine aloes is
generally supposed to be obtained from _aloë spica'ta_; but is referred by
De Candolle to a distinct species, A. SOCOTRI'NA; and by Martius, also to
_a. purpuras'cens_. Formerly this variety was brought from the Island of
Socotra or Zocotora (hence the name), by way of Smyrna and Malta; but it
is now chiefly obtained from Bombay and Madras.--_Char., &c._ Colour
garnet red to golden red; smell peculiar and aromatic, not unlike a
decaying russet apple, especially when fresh-broken, or breathed on, or
warmed; taste permanently and intensely bitter; fracture conchoidal;
softens in the hand, and becomes adhesive, yet retains considerable
brittleness; powder bright golden-yellow colour; central portions of the
lumps often soft, especially when first imported. "It is brittle, bitter,
of a reddish-brown colour, and an aromatic odour. Light permeates thin
recently broken laminæ." (Ph. L.) "In thin pieces, translucent and garnet
red; almost entirely soluble in spirit of the strength of sherry. Very
rare." (Ph. E.)
Socotrine aloes are always preferred for medicinal purposes, and are the
only variety used in perfumery, varnishes, and other nice purposes in the
arts.
=Aloes, Strained.= _Syn._ MELTED ALOES; ALOË COLA'TA, L. _Proc._ 1. The
aloes are melted in a copper pan, by the heat of steam or a water bath,
and are then pressed through a strong hair or wire sieve, and allowed to
cool.
2. As above, but with the addition of about twice its weight of water; the
decoction being strained and evaporated.
_Obs._ Mocha, Indian, and other common aloes, treated in this way and
coloured, are frequently sold for melted or strained 'Socotrines' and
'hepatics.' The colouring matter usually employed is the precipitated
carbonate of iron (sesquioxide), or Venetian red, in very fine powder,
with, sometimes, a little annatto. This fraud is not readily detected by
mere inspection, by those unaccustomed to these matters; and hence the
impunity with which it is perpetrated.
The object in melting aloes is to deprive it of the foreign matters, as
sand, leaves, pieces of wood, &c., which the commoner kinds generally
contain in large quantities. The action of the heat drives off much of
their nauseous smell, at the same time that it deepens their colour, and
renders their appearance more translucent and resinous, to the disguise of
their original nature. The operation, on the large scale, is usually
carried on at night, in consequence of the horribly nauseous fumes
evolved, which may be smelt at a great distance, and contaminate the
clothes of those engaged in it for a long time afterwards.
=AL'OES HEMP.= A plant growing in Peru, the East and West Indies, and
Mexico (_A. Americana_, _A. vivapara_, _A. f[oe]tida, &c._), where the
leaf is cultivated for its fibre, which is generally of a yellowish-white
colour, and used for rope-making.
=AL'OES WOOD.= _Syn._ AL'OE-WOOD; EAGLEWOOD; AGAL'LOCHUM (-k[)u]m),
LIG'NUM AL'OËS, L. AGAL'LOCHI, L. A. VE''RI, L. AQ'UILÆ, L. ASPAL'ATHI,
L.; AGALLOCHE, BOIS D'ALOÈS, Fr.; ALOEHOLZ, Ger.; CALAM'BAC, CALAM'BOUC,
Ind.; XYLO-AL'OËS[dagger]. A name applied to the wood of _alöex'ylon
agal'lochum_ (Lam.), a leguminous tree of Cochin China; and, though
apparently less correctly, to that of _aquila''ria agallochum_ and _a.
ova'ta_ (Lour.), trees of tropical Asia, belonging to a different nat.
order. Both are highly fragrant and aromatic; used in fumigations and
pastilles, and occasionally by cabinet makers and inlayers. The essential
oil of the wood, dissolved in spirit, was regarded by Hoffmann as one of
the best cordials and invigorants known. The same has also been said of a
tincture of its resin.
The same name and synonyms are popularly applied to the resin of the above
woods (ALOES-WOOD RESIN), of which there are two varieties:--the one,
light and porous, and filled with a highly fragrant resinous substance;
the other, denser and less resinous. It is an oily concretion in the
centre of the tree, the result of disease, which gradually hardens, and,
in time, kills it. It is highly fragrant, and is said to be nervine,
cephalic, cardiac, and stimulant. The powder is regarded as tonic and
astringent. Of all perfumes this is said to be the one most esteemed by
oriental nations.
=ALOE'TIC.= _Syn._ ALOËT'ICUS, L.; ALOÉTIQUE, Fr. Of or belonging to
aloes. In _medicine_, _pharmacy_, &c., applied to any preparation
containing aloes as a characteristic ingredient; made or obtained from
aloes. Substantively, an aloetic medicine.
=AL'OIN= (-o-[)i]n). C_{17}H_{18}O_{7}. [Eng., Fr.] _Syn._ AL'ÖIN;
ALOÏ'NA, L. The Messrs T. & H. Smith, of Edinburgh, have applied this name
to a crystalline substance, which they assert to be the pure cathartic
principle of aloes. Their process is to evaporate to the consistence of a
syrup, in vacuo, a solution obtained by exhausting a mixture of aloes and
sand, with cold water, and then to set it aside for a few days. The
resulting dark crystalline mass is purified by pressure between folds of
bibulous paper, and repeated crystallisation from hot water. Barbadoes
aloes are commonly used for the purpose; but soft or semi-liquid Socotrine
aloes, or the unevaporated Socotrine-aloes juice, is probably its best
source. Tilden gives the following process for the preparation of
aloin:--The aloes crushed small is to be dissolved in nine or ten times
its weight of boiling water acidified with sulphuric acid. After cooling
and standing for a few hours, the clear liquid is decanted from the resin,
and evaporated. The concentrated solution deposits a mass of yellow
crystals, which can be purified by washing, pressure, and
recrystallisation from hot spirit. After several recrystallisations the
aloin is obtained in the form of beautiful yellow needles, which are
pretty soluble in water and in alcohol, but soluble with difficulty in
ether.--_Dose_, 1 to 2 gr.
=ALOPE'CIA= (-sh'[)a]). [L.] _Syn._ AL'OPECY, FOX'-EVIL; ALOPÉCIE, Fr.;
FUCHSRAUDE, Ger. In _pathology_, baldness from disease, often extending to
the beard and eyebrows; as distinguished from 'calvities,' or ordinary
baldness arising from attenuation of the scalp or defective nutrition. See
BALDNESS.
=ALPAC'A.= A species of Llama, popularly known as the PERUVIAN SHEEP, an
animal intermediate between the camel and sheep, having long silky hair,
nearly as fine as that of the Cashmere goat. It was introduced to the
British manufacturers in 1834, when only 5700 lbs. of it was imported; but
it soon became an important article of commerce, the quantity imported
having gradually risen to above 2-1/4 millions of lbs. in 1853; whilst
the price has risen from about 9d. to 2s. 7d. the lb., in the same time.
The name is also given to fabrics woven from the wool of this animal; and
to others in fine wool, made in imitation of them. The gigantic factory,
&c., erected at Saltaire, Yorkshire, in 1852, for this manufacture, covers
about 12 acres of land. See LLAMA.
=ALPENKRAUTER-BRUST-TEIG= (Grablowitz, Gras). Pectoral cakes of Alpine
herbs. Gum arabic, 100 parts; sugar, 200 parts; extract liquorice, 1 part;
saffron, 1/8th part. Each box contains 48 lozenge-shaped yellowish cakes.
Made into a mass with decoction of marsh mallow. (Hager.)
=ALPENKRAUTER GESUNDHEIT'S LIQUEUR= (Rudolph Bohl). Medicinal liqueur of
Alpine herbs. A bottle containing 350 grammes of a liqueur which is an
extract of star anise, cassia, frangula bark, centaury, chicory, gentian,
and a little aloes. (Hager.)
=ALPENKRAUTER-MAGENBITTER= (Hauber). Stomachic bitters of Alpine herbs. A
brown liqueur of bitter, spirituous, and slightly aromatic flavour,
containing in 100 parts: oil of anise, 0·5; oil of cloves, 0·5; aloes,
1·5; alcohol, 40; water, 50. 157 grammes in each bottle. (Wittstein.)
=ALPHA-ORSELL'IC ACID.= See ORSELLIC ACID.
=ALPINE ROSE SOAP, SWISS.= A preservative against syphilitic infection (G.
A. Sarpe, Zurich). A glass cylinder corked and sealed, about 2 inches
long, and containing a hard brownish-grey mass weighing 12 grammes,
prepared thus:--Ammonia, 1 part; sublimate, 3 parts; tannin, 2 parts;
chloride of lime, 24 parts; Castile soap, 190 parts; oil of cloves, 1
part; spirit of wine, q. s. (Hager.)
=AL'QUIFOU= (-ke-f[=o][=o]). _Syn._ BLACK LEAD-ORE, POTTER'S ORE. A native
sulphide of lead used by potters to give a green glaze to coarse wares.
=ALSTONIA SCHOLARIS.= (Ind. Ph.) _Habitat._ Common in forests throughout
India.--_Officinal part._ The bark (_Alstoniæ cortex_). It occurs in
thick, irregular, more or less contorted pieces, easily broken. It
consists of a rough greyish epidermis, investing a buff or pale
cinnamon-coloured bark; internally, still lighter in colour,
and of a spongy texture, having a very bitter taste, but devoid
of odour.--_Properties._ Astringent, tonic, anthelmintic,
antiperiodic--_Therapeutic uses._ In chronic diarrh[oe]a and the advanced
stages of dysentery; also as a tonic in debility after fevers, and other
exhausting diseases.--_Dose._ 3 to 5 grains, either alone or combined, in
bowel affections, with small doses of ipecacuanha and extract of
gentian.--_Preparations._ TINCTURE OF ALSTONIA (_Tinctura Alstoniæ_). Take
of alstonia bark, bruised, 2-1/2 ounces; proof spirit, 1 pint. Macerate
for seven days in a closed vessel, with occasional agitation; filter, and
add sufficient proof spirit to make 1 pint. Or prepare by percolation, as
Tincture of Calumba.--_Dose_, 1 to 2 fluid drachms.
=Alstonia, Infusion of.= (_Infusum Alstoniæ._) Take of alstonia bark,
bruised, 1/2 an ounce; boiling water, 10 fluid ounces. Infuse in a covered
vessel for an hour and strain.--_Dose._ From 1 to 2 fluid ounces twice or
thrice daily. A good serviceable tonic.
=AL'TERATIVE= (awl'-t[)e]r-[)a]-t[)i]v). _Syn._ AL'TERANT*; AL'TERANS
([)a]l'-), L.; ALTÉRANT, ALTÉRATIF, Fr. In _medicine_, having power to
alter; applied to substances and agents which occasion a change in the
habit or constitution, and thus re-establish the healthy functions of the
body, or any part of it, without producing any sensible evacuation or
other obvious effect.
=ALTERATIVE EXTRACT=, or =GOLDEN MEDICAL DISCOVERY= (Dr Pierce, Buffalo),
for the cure of all severe, acute, chronic, or long-standing coughs,
inflammations, hoarseness, scrofulous, and syphilitic diseases. A clear
light-brown fluid, 220 grms., composed of 15 grms. purified honey, 1 grm.
extract of lettuce, 2 grms. laudanum, 100 grms. of proof spirit tasting of
fusel oil and wood spirit, and 105 grms. water. (Hager.)
=AL'TERATIVES= (-t[)i]vz). _Syn._ ALTERAN'TIA, L.; ALTÉRATIFS, &c., Fr.
Alterative medicines or agents. The preparations of mercury and iodine,
when properly administered, are the most useful members of this class; and
are those which are now the most generally employed.
=ALTHE'IN= ([)a]l-th[=e]'-[)i]n). _Syn._ ALTHÆ'INA, L. The name given by
Braconnot to a substance identical with asparagin, which he discovered in
the 'marsh-mallow' (_althæ'a officina'lis_, Linn.).
=ALTHOFF WATER= (aqua mirabilis), for torpid ulcers. Wine vinegar, 750
parts; sulphate of copper, 100 parts; potash, 25 parts; ammonia, 30 parts;
salt of sorrel, 8 parts; French brandy, 375 parts. Digest for a few days
in a glass vessel and distil to dryness from a glass retort. (Wittstein.)
=AL'UDEL= (-[=u]-). In _chemistry_, a pear-shaped glass or earthen pot
open at both ends, formerly much used for connecting other vessels in the
process of sublimation. A number of them joined together are still
employed for the distillation of quicksilver, in Spain.
=AL'UM= K_{2}SO_{4}.Al_{2}(SO_{4})_{3}.24Aq. _Syn._ POT'ASH-ALUM,
SUL'PHATE OF ALUMINUM AND POTASSIUM, COMMON ALUM; ALU'MEN, A. POTAS'SICUM,
L.; ALUN, SULFATE D'ALUMINE ET DE POTASSE, Fr.; ALAUN, Ger.; ALUME, Ital.
The principal alum-works in England, until recently, were those of Lord
Glasgow, at Hurlett and Campsie, near Glasgow, and those of Lords Dundas
and Mulgrave, at Whitby, Yorkshire (est. 1600); but those of Mr Spence, at
Manchester, and at Goole (Yorkshire), and of Mr Pochin, at Manchester, are
now among the largest, if they be not actually the largest in the world.
There are also extensive alum-works at and near Newcastle-on-Tyne; but
none of importance, that we know of, in any other part of these realms.
_Nat. hist._ Alum is found native in some places (NATIVE ALUM), either
effloresced on the surface of bituminous alum-schist (Göttwigg, Austria);
or united with the soil in the neighbourhood of volcanoes (Solfatara,
Naples); when it may be obtained by simple lixiviation and evaporation, a
little potash being commonly added to convert the excess of sulphate of
alumina present into alum. It is also found in certain mineral waters
(East Indies).
_Sources._ The alum of commerce is usually obtained from schistose pyritic
clays, commonly termed alum-ores, aluminous shale, a.-schist, &c.; and
from alum-rock, a.-stone, or alunite. At La Tolfa, Civita Vecchia, where
the best Roman-alum is produced, the source is stratified alum-stone. On
the Continent, and in Great Britain, it is generally pyritaceous clays,
volcanic aluminous ores, aluminous shale, or alum-slate. These minerals
contain sulphide of iron, alumina, bitumen or carbon, and frequently a
salt of potassium. Of late years large quantities of alum have been
prepared on the banks of the Tyne from aluminous clay.
_Prep._ The manufacture of alum is technically said to be conducted
according to the natural process when prepared from alum-schist or
alum-ore; and according to the artificial process when made by acting on
clay with sulphuric acid, and adding a potassium salt to the resulting
lixivium. The manufacture of alum and of sulphate of alumina from such
materials as contain only alumina, to which consequently sulphuric acid
and alkaline salts have to be added, has come largely into practice in
England. The materials employed are, in addition to clay, cryolite or
Greenland spar, a fluoride of aluminum and soda; bauxite, a hydrate of
alumina, of more or less purity; and slag. The following are the details
of these processes:--
_a._ From ALUM-ORE, ALUMINOUS SCHIST, or SHALE, &c.:--
[Illustration]
1. The mineral (alum-ore, a.-schist, &c.) is placed in heaps, and
moistened from time to time with water, when it becomes gradually hot, and
falls into a pulverulent state. This decomposition commonly occurs either
wholly, or partially, on the floor of the mine. If the ore does not
possess this property on mere exposure to air and moisture, it is broken
into pieces and laid upon a bed of brushwood and small coal, to the depth
of about four feet, when the pile is fired and fresh lumps of the
alum-mineral thrown on, until the mass becomes of considerable height and
size. The combustion, as soon as established, is conducted with a
smothered fire, until the calcination is complete; care being taken to
prevent fusion, or the disengagement of either sulphurous or sulphuric
acid, from contact between the ignited stones and the carbonaceous
fuel.[35] To promote these ends the pile, at the proper time, is 'mantled'
(as the workmen call it) or covered with a layer of already calcined and
exhausted ore, in order to protect it from high winds and heavy rains; as
also to moderate the heat, and let it proceed gradually, so that the
sulphur present may not be lost or wasted by volatilisation. The roasting
is finally checked by a thicker 'mantling,' and the whole allowed to cool.
By this time the pile has usually lost about one half its bulk, and become
open and porous in the interior, so that the air can circulate freely
through the mass; the latter, in dry weather, as the heap cools, being
usually promoted by sprinkling a little water on it, which, by carrying
down some of the saline matter, renders the interior still more open to
the atmosphere. The whole, when cold, or nearly cold, is, if necessary,
still further exposed to the action of air and moisture. The time required
to calcine the heap properly, including that taken by the burned ore to
cool, varies, according to its size and the state of the weather, from
three to nine, or even twelve months. The residuum of the calcination is
next placed in large stone or brick cisterns, and edulcorated with water,
until all the soluble portion is dissolved out; the solution is then
concentrated in another stone cistern, so made that the flame and heated
air of its reverberatory furnace sweep the whole surface of the liquor.
(See _engr._) The evaporation is continued until it just barely reaches
the point at which crystals are deposited on cooling; when it is run off
into coolers. After the sulphate of iron, always present, has been
deposited in crystals, the mother-liquor, containing the sulphate of
aluminum, is run into other cisterns, and a saturated solution of chloride
of potassium, or of sulphate of potassium, or (sometimes) impure sulphate
or carbonate of ammonium, or a mixture of them,[36] is added until a cloud
or milkiness ceases to be produced on addition of more.[37] It is next
allowed to settle and get thoroughly cold, and the supernatant
'mother-liquor' being drawn off with a pump or syphon, the precipitate,
which is alum in the form of minute crystals (technically termed 'flour'),
is well drained, and subsequently washed by stirring it up with a little
very cold water, which is then drained off, and the operation repeated a
second time with fresh water. A saturated solution of the pulverulent alum
('flour') is next formed in a leaden boiler, and the clear portion is run
or pumped off, while boiling hot, into crystallising vessels, called
roaching casks (see _engr._), the staves of which are lined with lead, and
nicely adjusted to each other. After the lapse of a week or ten days, the
hoops and staves of these 'casks' are removed, when a thick crust of
crystallised alum is found, which exactly corresponds in form and size to
the interior of the cask. A few holes are then made in the sides of this
mass, near the bottom, to allow the contained mother-liquor to drain off,
after which the whole is broken up and packed in casks for sale. Sometimes
the alum thus obtained, or the lower portion of it, is washed with a
little very cold water, and, if discoloured, or small or slimy, is
purified by a second crystallisation.
[Footnote 35: The generality of alum-minerals require roasting; and their
own bituminous matter is, in many cases, sufficient to produce the heat
required, which need not necessarily exceed 600 to 650° Fahr., provided it
be continued for a sufficient period. It is only when they are less
bituminous or carbonaceous that slack or saw-dust, &c., is employed.]
[Footnote 36: For pure POTASH-ALUM a salt of potash only must be employed.
When ammonia (usually in the form of gas-liquor or gas-sulphate) is used
as the precipitant, the product is AMMONIA-ALUM. The ordinary alums of
commerce are now generally mixtures of the two.]
[Footnote 37: The respective quantities required to produce 100 parts of
alum from the sulphate of alumina liquor are--
Chloride of potassium 15·7
Sulphate of " 18·4
" ammonium 13·9
In practice, the exact quantity required may be found by a previous trial
of a little of the aluminous liquor; but the indications mentioned in the
text will always show the operator when a sufficient dose is added.]
[Illustration]
2. As ammonia-alum (Spence's process; see _below_), but using a
potash-salt as the precipitant, either wholly or in part, instead of
ammonia; and, in the latter case, supplementing the deficiency of potash
with ammonia, as there explained.
_b._ From ALUMINOUS CLAY and OIL OF VITRIOL:--
1. Clay, free or nearly free from carbonate of lime and oxide of iron, is
chosen for this purpose. It is moderately calcined (in lumps) in a
reverberatory furnace, until it becomes friable; great care being taken
that the heat be not sufficient to indurate it, which would destroy its
subsequent solubility. It is next reduced to powder, sifted, and mixed
with about 45% of its weight of sulphuric acid (sp. gr. 1·45), the
operation being conducted in a large stone or brick basin arched over with
brickwork. Heat is then applied, the flame and hot air of a reverberatory
furnace being made to sweep over the surface of the liquor. The heat and
agitation are continued for 2 or 3 days, when the mass is raked out and
set aside in a warm place for a few weeks (6 to 8), to allow the acid the
more perfectly to combine with the clay. At the end of this time the
newly-formed sulphate of alumina is washed out, the solution evaporated
until of a sp. gr. of about 1·38 (1·24 for 'ammonia-alum'), and the salt
of potash added. The remaining operations resemble those above described.
Good alum may be produced by this process at about two thirds the cost of
rock or mine alum.
2. (Process of Mr Pochin.) Fine China clay is heated in a furnace, and
mixed with a suitable proportion of sulphuric acid; the latter being
considerably diluted with water, in order to moderate its action, which
would otherwise be far too violent. The mixture is then passed into
cisterns furnished with movable sides, where, in a few minutes, it heats
violently and boils. The thick liquid gradually becomes thicker, until it
is converted into a solid porous mass; the pores being produced by the
bubbles of steam which are driven through it, owing to the heat resulting
from the reaction of the ingredients on each other. This porous mass
(ALUM-CAKE; CONCENTRATED ALUM) appears perfectly dry, although retaining a
large amount of combined water. It also contains all the silica of the
original clay, but in such a state of fine division, that the whole
appears homogeneous; whilst it imparts a dryness to the touch which can
scarcely be given to pure sulphate of alumina. From this substance a
solution of pure sulphate of alumina is easily obtainable by lixiviation,
and allowing the resulting solution to deposit its silica before using it,
but for many purposes the presence of the finely divided silica is not
objectionable. The sulphate of alumina solution so obtained is adapted to
all the purposes in dyeing for which alum is now employed; the sulphate of
potash or of ammonia in the latter being an unnecessary constituent, and
one merely added to facilitate the purification and subsequent
crystallisation of the salt. To obtain ALUM from the porous alum-cake, the
proper proportion of acid having been used in its preparation, or
subsequently added, it is only necessary to precipitate its concentrated
solution with a strong solution of a salt of potash, or of ammonia, or a
mixture of them, and to otherwise proceed as before.
_Ratio._ In the above process the sulphide of iron of the shale or schist
is converted by atmospheric oxygen into sulphate of iron and sulphuric
acid; the sulphuric acid decomposes the clay, setting silica free, and
producing sulphate of aluminum. The sulphate of iron is mostly got rid of
by concentrating the solution of the mixed sulphates, and the
mother-liquors are converted into alum by the addition of the salt of
potassium. When chloride of potassium is used, it yields chloride of iron
and sulphate of potassium, the latter combining with the sulphate of
aluminum, and the former remaining behind in the mother-liquor. See ALUMS
(in Chemistry).
_Comp._ Potassium alum has the formula
K_{2}SO_{4}.Al_{2}(SO_{4})_{3}.24Aq.
_c._ From CRYOLITE.
1. (Thomson's method.) Decomposition of cryolite by ignition with
carbonate of lime. From the ignited mass the aluminate of soda is obtained
by lixiviation with water, and into the solution carbonic acid gas is
passed, when there result precipitated hydrated gelatinous alumina and
carbonate of soda, which remains in solution. If it be desired to obtain
the alumina as an earthy compact precipitate, bicarbonate of soda is used
instead of carbonic acid. While the clear liquor is boiled down for the
purpose of obtaining carbonate of soda, the precipitated alumina is
dissolved in dilute sulphuric acid; this solution is evaporated for the
purpose of obtaining sulphate of alumina (the so-called concentrated
alum), or the solution after having been treated with a potassa or an
ammonia salt is converted into alum.
2. (Sauerwein's method.) Decomposition of cryolite by caustic lime by the
wet way. Very finely ground cryolite is boiled with water and lime, the
purer the better, and as free from iron as possible, in a leaden pan. The
result is the formation of a solution of aluminate of soda, and insoluble
fluoride of calcium (lime). When the fluoride of calcium has deposited,
the clear liquid is decanted, and the sediment washed, the first
wash-water being added to the decanted liquor, and the second and third
wash-waters being used instead of pure water at a subsequent operation. In
order to separate the alumina from the solution of aluminate of soda,
there is added to the liquid while being continuously stirred very finely
pulverised cryolite in excess, the result of the decomposition being
alumina and fluoride of sodium, (soda). When no more caustic soda can be
detected in the liquid, it is left to stand for the purpose of becoming
clear. The clarified solution of fluoride of sodium is then drawn off, and
the alumina treated as above described. The solution of fluoride of sodium
having been boiled with caustic lime yields a caustic soda solution, which
having been decanted from the sediment of fluoride of calcium is
evaporated to dryness. Recently the fluoride of calcium occurring as a
by-product has been used in glass-making.
3. The decomposition of cryolite by sulphuric acid yields sulphate of soda
convertible into carbonate by Leblanc's process, and sulphate of alumina
free from iron. This method of decomposing cryolite is, however, by no
means to be recommended, as owing to the liberation of hydrofluoric acid,
peculiarly constructed apparatus are required, whilst the sulphate of soda
has to be converted into carbonate.
_d._ From Bauxite. This mineral, occurring in some parts of Southern
France, in Calabria, near Belfast, and in other parts of Europe, consists
essentially (viz. 60 per cent.) of hydrate of alumina, more or less pure.
In order to prepare alums and sulphate of alumina from it, the mineral is
first disintegrated by being ignited with carbonate of soda, or with a
mixture of sulphate of soda and charcoal; in each case the lixiviation of
the ignited mass yields aluminate of soda, from which, by the processes
already described under "Cryolite," alum, or sulphate of alumina, and soda
are prepared.
_e._ From blast-furnace slag. Lürmann recommends the slag to be decomposed
by means of hydrochloric (muriatic) acid. From the resulting solution of
chloride of aluminum the alumina is precipitated by carbonate of lime, any
dissolved silica being precipitated at the same time. The alumina is
dissolved in sulphuric acid, leaving the silica.
[Illustration]
_Prop._ Alum crystallises in regular octahedrons, often with truncated
edges and angles; (see _engr._); and sometimes in cubes, but only when
there is a deficiency of acid in its composition, with the alkali in
slight excess of the proper quantity. (Löwel.)[38] It is slightly
efflorescent in dry air: soluble in 18 parts of cold water, and in rather
less than its own weight of boiling water; tastes sweet, acidulous, and
very astringent; is styptic; and reddens litmus. When heated it melts,
loses its water of crystallisation, and becomes white and spongy (DRIED
ALUM); a strong heat, short of whiteness, decomposes it, with the
evolution of oxygen and a mixture of sulphuric and sulphurous anhydride;
calcined with carbonaceous matter it suffers decomposition, and furnishes
a pyrophoric residuum (HOMBERG'S PYRO'PHORUS). Ignited with alkaline
chlorides, hydrochloric acid is liberated; which also occurs when their
concentrated solutions are boiled together. Ammonia precipitates pure
hydrate of aluminum from potassium alum; but only a subsulphate from the
simple sulphate of alumina. Sp. gr. 1·724; but, when containing ammonia,
often so low as 1·710.
[Footnote 38: The ordinary alum, of commerce, consisting of large
crystalline masses, which do not present any regular geometrical form; but
by immersion in water for a few days, octahedral and rectangular forms are
developed on its surface. (Daniell.)]
_Tests, &c._ It is easily recognised by its crystalline form, its taste,
and by its complete solubility in water. Its aqueous solution gives a
white gelatinous precipitate soluble in excess; a platinum wire moistened
with the solution imparts a violet colour to the blowpipe flame; and
chloride of barium gives a white precipitate insoluble in nitric acid.
_Pur._ When pure, its solution is not darkened by tincture of galls,
sulphuretted hydrogen or ferrocyanide of potassium; neither does it give
any precipitate with solution of nitrate of silver. Heated with caustic
potassa, or quick-lime, it does not evolve fumes of ammonia.
_Adult., &c._ The principal impurity, and one which renders alum unfit for
the use of the dyer, is iron. This may be readily detected by the blue
precipitate it gives with ferrocyanide of potassium, or the black
precipitate with sulphide of ammonium, which are very delicate tests.[39]
Lime, another very injurious contamination, may be detected by
precipitating the alumina and iron (if any) with ammonia, and then adding
oxalate of ammonia to the boiled and filtered liquid. The liquid filtered
from the last precipitate (oxalate of lime) may still contain magnesia,
which may be detected by the white precipitate caused on the addition of
an alkaline phosphate. Common alum frequently contains ammonia, from
urine, or the crude sulphate of the gas-works, having been employed in its
manufacture. Powdered alum is frequently adulterated with common salt, in
which case it gives a white curdy precipitate with nitrate of silver,
turning black by exposure to the light.
[Footnote 39: Good English alum contains less than 0·1% of iron. The best
Roman or Italian alums seldom contain more than ·005% of iron-alum,
notwithstanding their exterior colour.]
_Phys. eff. &c._ In small quantities alum acts as an astringent; in larger
doses as an irritant. It acts chemically on the animal tissues and fluids,
is absorbed, and has been discovered in the liver, spleen, and urine
(Orfila), the last often becoming acid (Kraus). Externally, it is
astringent. The almost general use of alum by the English bakers is one of
the most fertile sources of dyspepsia and liver and bowel complaints in
adults; and of debility and rickets in children. Bad teeth and their early
decay is another consequence of the daily use of alum in our food. The
bone matter (phosphate of lime) of bread, instead of being assimilated by
the system, is either wholly, or in part, converted into a salt of
alumina, which is useless and incapable of appropriation. When alum has
been taken in poisonous doses an emetic should be given, followed by warm
diluents and demulcents, containing a little carbonate of soda; and
subsequently by a purgative.
_Uses, &c._ The applications of alum in the arts and manufactures are
numerous and important. It is used to harden tallow and fats; to render
wood and paper incombustible; to remove greasiness from printers' blocks
and rollers; to prepare a paper for whitening silver and silvering brass
in the cold; to help the separation of the butter from milk; to purify
turbid water; to dress skins; to fix and brighten the colours in dyeing;
to make lake and pyrophorus, &c., &c. It is also extensively used for
clarifying liquors, and for many other purposes connected with the arts
and everyday life. In _medicine_, alum is used as a tonic and astringent,
in doses of 5 to 20 gr.; as a gargle (1 dr. to 1/2 pint of water); and as
a collyrium and injection (10 to 15 gr. to 6 oz. of water). In lead colic,
1/2 to 1 dr. of alum (dissolved in gum-water), every 3 or 4 hours, is said
to be infallible. Powdered alum is frequently applied with the tips of the
fingers, in cases of sore throat and ulcerations of the mouth, &c. A
teaspoonful of it is said to be one of the very best emetics in croup. (Dr
Meigs.) Alkalies, alkaline carbonates, lime, magnesia, acetate of lead,
astringent vegetables, &c., are incompatible with it.
_Gen. commentary._ In addition to the particulars of its manufacture given
above, we may add, that the plan of getting rid of the ferric salts there
referred to has to some considerable extent been successfully replaced by
that of precipitating the alum, instead of the sulphate of iron, by adding
alkaline matter to the lixivium. The crystalline precipitate is purified
by draining, re-solution, and re-crystallisation; whilst the sulphate of
iron and Epsom-salts contained in the mother liquor are obtained by
subsequent evaporation and crystallisation; after which a fresh crop of
alum may be got from it, by the use of an alkaline precipitant, as before.
In estimating the strength of his solution the alum-maker takes as a
standard a measure or sp. gr. bottle capable of holding exactly 80
pennyweights of distilled water. The excess of the weight of liquor, in
pennyweights, over 80, or that of water, is called so many 'pennyweights
strong.' Thus one of 90 pennyweights (90 dwt.) is said to be '10 dwt.
strong,' or simply, 'one of 90 dwt.' These numbers correspond to 2-1/2
degrees of Twaddle's hydrometer, and may easily be found by dividing
Twaddle's degrees by 2·5 or 2-1/2; or by multiplying them by 4, and
pointing off the right-hand figure of the product for a decimal. The
result is in alum-makers' pennyweights.
By a patent now expired (Weisman's, 1839) the ferric salts are
precipitated by the addition of a solution of ferrocyanide of potassium
(prussiate of potash); after which the supernatant clear liquor, which is
now a solution of nearly pure sulphate of alumina, is decanted, and
evaporated for future operations, until it either forms, on cooling, a
concrete mass, which is moulded into bricks or lumps, for the convenience
of 'packing,' or until it is sufficiently concentrated to be converted
into ALUM by the addition of a salt of potash or of ammonia in the usual
manner. The product, in each case, is perfectly free from iron. By a like
addition of the ferrocyanide to a solution of ordinary sulphate of
aluminia or alum, the dyer may himself easily render them free from
iron, or iron-alum; when, as mordants for even the most delicate colours,
they are equal to the very best Roman alum.
Another process has been patented (Barlow & Gore, 1851) for the
manufacture of alum from the ash or residue of the combustion of
Boghead-coal, which, though hitherto regarded as almost valueless,
actually contains about 30% of alumina. It has not, however, been found a
convenient material for the purpose.
By the latest and most approved processes the least possible quantity of
boiling water or liquor is employed for making the solutions, so that they
may crystallise without evaporation, and thus economise fuel; and the
mother-liquors of previous operations are constantly employed for this
purpose, when possible. Nor is anything which is convertible to use, from
the drainage of the heaps, to the liquor and slime of the roaching casks,
allowed to be wasted.
By whatever process, or from whatever materials alum is obtained, it is
absolutely necessary for the successful and economical conduct of its
manufacture, that the precise composition of the mineral or minerals
employed should be exactly known. This can only be determined by actual
analysis, which should be extended to several parts of the same bed, and
particularly to the upper and lower strata, which frequently differ in
composition from each other, and thus require different treatment, or may
be most advantageously employed in combinations with each other. The
necessity of this will be seen by reference to the composition of the
following minerals, of which the top contains a larger proportion of
iron-pyrites than the bottom, and the two require to be mixed, to equally
diffuse the sulphuric acid generated by the calcination, &c., to which
they are subjected.