m. and a pop. (1904) of 14,857, of whom 40% are whites.
Aliwal North was so called to distinguish it from Aliwal
South, now Mossel Bay, the seaport of the pastoral Grasveld
district, on the west side of Mossel Bay. Both places were
named in honour of Sir Harry Smith, governor of Cape Colony
1847-1852, Aliwal (see above) being the village in the Punjab
where in 1846 he gained a great Victory over the Sikhs.
Crossing the Orange River at this spot in September 1848, Sir
Harry noted that it was ``a beautiful site for a town,'' and
in the May following the town was founded. In the early months
of the Boer War of 1899-1902 Aliwal North was held by the
Boers. It was reoccupied by the British in March 1900.
ALIZARIN, or 1.2 DIOXYANTHRAQUINONE,
/CO\
C6H4 C6H2(OH)2[1.2],
\CO/
a vegetable dyestuff formerly prepared from madder root (Rubia
tinctorum) which contains a glucoside ruberythric acid
(C26H28O14). This glucoside is readily hydrolysed by
acids or ferments, breaking up into alizarin and glucose:
C26H28O14 + 2H2O = 2C6H12O6 + C14H8O4
Ruberythric acid = Glucose + Alizarin.
Alizarin was known to the ancients, and until 1868 was obtained
entirely from madder root. The first step in the synthetical
production of alizarin was the discovery in 1868 of C. Graebe
and C. Liebermann that on heating with zinc dust, alizarin
was converted into anthracene. In order to synthesize
alizarin, they converted anthracene into anthraquinone and
then brominated the quinone. The dibrominated product so
obtained was then fused with caustic potash, the melt dissolved
in water, and on the addition of hydrochloric acid to the
solution, alizarin was precipitated. This process, owing
to its expensive nature, was not in use very long, being
superseded by another, discovered simultaneously by the
above-named chemists and by Sir W. H. Perkin; the method being
to sulphonate anthraquinone, and then to convert the sulphonic
acid into its sodium salt and fuse this with caustic soda.
In practice, the crude anthracene is purified by solution
in the higher pyridine bases, after which treatment it is
frequently sublimed. It is then oxidized to anthraquinone
by means of sodium dichromate and sulphuric acid in leaden
vats, steam heated so that the mixture can be brought to the
boil. When oxidation is complete the crude anthraquinone
is separated in filter presses and heated with an excess
of commercial oil of vitriol to 120 deg. C., the various
impurities present in the crude material being sulphonated
and rendered soluble in water, whilst the anthraquinone is
unaffected; it is then washed, to remove impurities, and
dried. The anthraquinone so obtained is then heated for
some hours at about 150-160 deg. C. with fuming sulphuric acid
(containing about 40-50% SO3), and by this treatment is
converted into anthraquinone-b-monosulphonic acid. The
solution is poured into water and sodium carbonate is added
to neutralize the excess of acid, when the sodium salt of
the monosulphonic acid (known as silver salt) separates out
This is filtered, washed, and then fused with caustic soda,
when the sulpho-group is replaced by a hydroxyl group, and a
second hydroxyl group is simultaneously formed; in order to
render the formation of this second group easier, a little
potassium chlorate or sodium nitrate is added to the reaction
mixture. The melt is dissolved in water and the dyestuff is
liberated from the sodium salt by hydrochloric or sulphuric
acid, or is converted into the calcium salt by digestion with hot
milk of lime, then filtered and the calcium salt decomposed by
acid. The precipitated alizarin is then well washed and made
into a paste with water, in which form it is put on to the market.
K. Lagodzinski (Berichte, 1895, 28, p. 1427) has synthesized
alizarin by condensing hemipinic acid [(CH3O)2C6H2(COOH)2]
with benzene in the presence of aluminium chloride. The
product on acidification gives a compound C15H12O5.H2O
which is probably an oxy-methoxy-benzoyl benzoic acid. This
is dissolved in cold concentrated sulphuric acid, in which
it forms a yellowish red solution, but on heating to 100 deg.
C. the colour changes to red and violet, and on pouring out
upon ice, the monomethyl ether of alizarin is precipitated.
This compound is hydrolysed by hydriodic acid and alizarin is
obtained. It can also be synthesized by heating catechol
with phthalic anhydride and sulphuric acid at 150 deg. C.
/CO\ /CO\
C6H4 O + C6H4(OH)2[1.2] = H2O + C6H4 C6H2(OH)2.
\CO/ \CO/
Pure alizarin crystallizes in red prisms melting at 200 deg.
C. It is insoluble in water, and not very soluble in
alcohol. It dissolves readily in caustic alkalis on account
of its phenolic character, and it forms a yellow-coloured
di-acetate. Its value as a dyestuff depends on its power of
forming insoluble compounds (lakes) with metallic oxides. It
has no affinity for vegetable fibres, and consequently cotton
goods must be mordanted before dyeing with it (see DYEING.)
Numerous derivatives of alizarin are known. On solution in
glacial acetic acid and addition of nitric acid, b-nitroalizarin
OH
|
(alizarin orange) / \ /CO\ / \OH
| | | |
\ / \CO/ \ /NO2
is produced, and this on heating with sulphuric
acid and glycerin is converted into alizarin blue.
The trioxyanthraquinones--purpurin, anthrapurpurin, anthragallol
and flavopurpurin---are also very valuable dyestuffs. These
compounds may be represented by the following formulae:
OH OH OH OH
| | | |
/ \ /CO\ / \OH HO/ \ /CO\ / \OH / \ /CO\ / \OH / \ /CO\ / \OH
| | | | | | | | | | | | | | | |
\ / \CO/ \ / \ / \CO/ \ / HO\ / \CO/ \ / \ / \CO/ \ /OH
|
OH
Purpurin. Anthrapurpurin. Flavopurpurin. Anthragallol.
Purpurin (1.2.4 trioxyanthraquinone) is found with
alizarin in madder root; it is now prepared synthetically
by oxidizing alizarin with manganese dioxide and sulphuric
acid. After the separation of the silver salt (see above)
obtained on sulphonating anthraquinone, the remaining acid
liquid gives on treatment with calcium carbonate the calcium
salt of anthraquinone 2.6 disulphonic acid (anthraquinone-
a-disulphonic acid). This is converted into the sodium salt
by means of sodium carbonate, and on alkali fusion yields
fiavopurpurin. In a similar manner anthrapurpurin is
prepared by alkali fusion of anthraquinone 2.8 disulphonic
acid. Anthragallol is synthetically prepared by the
condensation of benzoic and gallic acids with sulphuric acid
OH OH
| |
/ \COOH / \OH / \ /CO\ / \OH
| | + | | = 2 H2O + | | | |
\ / HOOC\ /OH \ / \CO/ \ /OH
or from pyrogallol and phthalic anhydride in
the presence of sulphuric acid or zinc chloride.
A. Baeyer in 1890, by heating alizarin with fuming sulphuric
acid for 24-48 hours at 35-40 deg. C., obtained a product, which
after treatment with caustic soda gave a sulphuric acid ester
of quinalizarin, and this after acidification and boiling was
converted into quinalizarin (Alizarin Bordeaux) or 1.2.6.9
tetra-oxyanthraquinone. Penta-oxyanthraquinones have been
obtained from purpurin and anthrapurpurin, while a hexa-
oxyanthraquinone has been obtained from 1.5 dinitro- anthraquinone.
ALKAHEST (a pseudo-Arabic word believed to have been invented by
Paracelsus), a liquid, much sought after by the alchemists, having
the power of dissolving gold and every other substance, which
it was supposed would possess invaluable medicinal qualities.
ALKALI, an Arabic term originally applied to the ashes of
plants, from which by lixiviation carbonate of soda was obtained
in the case of sea-plants and carbonate of potash in that of
land-plants. The method of making these ``mild'' alkalis into
``caustic'' alkalis by treatment with lime was practised in
the time of Pliny in connexion with the manufacture of soap,
and it was also known that the ashes of shore-plants yielded
a hard soap and those of land-plants a soft one. But the
two substances were generally confounded as ``fixed alkali''
(carbonate of ammonia being ``volatile alkali''), till Duhamel
du Monceau in 1736 established the fact that common salt and
the ashes of sea-plants contain the same base as is found in
natural deposits of soda salts (``mineral alkali''), and that
this body is different from the ``vegetable alkali'' obtained
by incinerating land- plants or wood (pot-ashes). Later,
Martin Heinrich Klaproth, finding vegetable alkali in certain
minerals, such as leucite, proposed to distinguish it as
potash, and at the same time assigned to the mineral alkali the
name natron, which survives in the symbol, Na, now used for
sodium. The word alkali supplied the symbol for potassium,
K (kalium.) In modern chemistry alkali is a general term
used for compounds which have the property of neutralizing
acids, and is applied more particularly to the highly soluble
hydrates of sodium and potassium and of the three rarer ``alkali
metals,'' caesium, rubidium and lithium, also to aqueous
ammonia. In a smaller degree these alkaline properties are
shared by the less soluble hydrates of the ``metals of the
alkaline earths,'' calcium, barium and strontium, and by thallium
hydrate. An alkali is distinguished from an acid or neutral
substance by its action on litmus, turmeric and other indicators.
ALKALI MANUFACTURE. The word ``alkali'' denotes both soda and
potash, but by ``alkali manufacture'' we understand merely
the manufacture of sodium sulphate, carbonate and hydrate.
The corresponding potash compounds are not manufactured in
the United Kingdom, but exclusively in Germany (from potassium
chloride and from the mother-liquor of the strontia process
in the manufacture of beetroot sugar) and in France (from
vinasse) . The term alkali is employed in a technical sense
for the carbonate and hydrate (of sodium), but since in the
Leblanc process the manufacture of sodium sulphate necessarily
precedes that of the carbonate, we include this as well as
the manufacture of hydrochloric acid which is inseparable from
it. We also treat of the utilization of hydrochloric acid
for the manufacture of chlorine and its derivatives, which
are usually comprised within the meaning of the term ``alkali
manufacture.'' A great many processes have been proposed
for the manufacture of alkali from various materials, but
none of these has become of any practical importance except
those which start from sodium chloride (common salt); and
among the latter again only three classes of processes
are actually employed for manufacturing purposes, viz. the
Leblanc, the ammonia-soda, and the electrolytic processes.
I. THE LEBLANC PROCESS
The Leblanc process, which was invented by Nicolas
Leblanc (q.v.) about 1790, begins with the decomposition
of sodium chloride by sulphuric acid, by which sodium
sulphate and hydrochloric acid are produced. The sodium
sulphate is afterwards fluxed with calcium carbonate and
coal, and a mixture is thus obtained from which sodium
