lead. The latter dissolves the sodium as it is formed and
carries it to an outer compartment where by the action of
water the sodium is converted into caustic soda, while the
lead returns to the inner compartment. This process is carried
on at Niagara Falls, but it is uncertain to what extent.
(5) The Hargreaves-Bird process avoids certain drawbacks
attached to other processes, by employing a wire diaphragm
and converting the caustic soda as it issues on the other
side of this, by means of carbon dioxide, into a mixture
of sodium carbonate and bicarbonate, which separates out
in the solid state. This process is but little used.
It stands to reason that the electrolytic processes have
been principally developed in localities where the electric
current can be produced in the cheapest possible manner by
means of water power, but this is not the only condition
to be considered, as the question of freight to a centre of
consumption and other circumstances may also play an important
part. Where coal is very cheap indeed and the other
conditions are favourable, it is possible to establish such
an industry with a prospect of commercial success, even when
the electric current is produced by means of steam-engines.
Natural Soda.--This is the term applied to certain
deposits of alkaline salts, or their solutions, which occur,
sometimes in very large quantities, in various parts of the
world. The oldest and best known of these are the Natron
lakes in Lower Egypt. The largest occurrence of natural soda
hitherto known is that in Owen's Lake and other salt lakes
situated in eastern California. The soda in all of these
is present as ``sesquicarbonate,'' in reality 4/3 carbonate:
NaHCO3.Na2CO3.2H2O, and is always mixed with large
quantities of chloride and sulphate, which makes its extraction
more difficult than would appear from the outset. Hence,
although for many centuries (up to Leblanc's invention)
hardly any soda was available except from this source, and
although we now know that millions of tons of it exist,
especially in the west of the United States, there is as yet
very little of it practically employed, and that only locally.
REFERENCES.--The principal work on the manufacture of alkali
is G. Lunge's Sulphuric Acid anid Alkali (2nd ed., vols. ii.
and iii., 1895-1896). This work has also appeared in a German
and a French edition. The same author wrote the articles
on the manufacture of sodium and potassium compounds and on
chlorine in Thorpe's Dictionary of applied Chemistry (3
vols., 1890-1893). The subject is also treated, very much
more briefly, in Sorel's Industrie chimique minerale
(1902), and of course in every other general treatise on
chemical technology. A special treatise on the manufaciure
of ammonia soda ash has been published in German by H.
Schreib. Consult also the official Annual reports on Alkali,
&c., and, from 1864 onwards, Journal of the Society of
Chemical Industry, Fischers Jahresberichte der chemischen
Technologie, and Zeitschrift fur angewandte Chemie. (G. L.)
ALKALINE EARTHS. The so-called alkaline earth-metals are
the elements beryllium, magnesium, calcium, strontium and
barium. By the early chemists, the term earth was used to
denote those non-metallic substances which were insoluble in
water and were unaffected by strong heating; and as some of
these substances (e.g. lime) were found to be very similar in
properties to those of the alkalis, they were called alkaline
earths. The alkaline earths were assumed to be elements until
1807, when Sir H. Davy showed that they were oxides of various
metals. The metals comprising this group are never found in
the uncombined condition, but occur most often in the form
of carbonates and sulphates; they form oxides of the type RO,
and in the case of calcium, strontium and barium, of the type
RO2. The oxides of type RO are soluble in water, the solution
possessing a strongly alkaline reaction and rapidly absorbing
carbon dioxide on exposure; they are basic in character and
dissolve readily in acids with the formation of the corresponding
salts. As the atomic weight of the element increases, it is
found that the solubility of the sulphates in water decreases.
Beryllium to a certain extent stands alone in many of its
chemical properties, resembling to some extent the metal
aluminium. Beryllium and magnesium are permanent in dry air;
calcium, strontium and barium, however, oxidize rapidly on
exposure. The salts of all the metals of this group usually
crystallize well, the chlorides and nitrates dissolve readily
in water, whilst the carbonates, phosphates and sulphates
are either very sparingly soluble or are insoluble in water.
ALKALOID, in chemistry, a term originally applied to any
organic base, i.e. a nitrogenous substance which forms
salts with acids; now, however, it is usual to restrict
the term to bases of vegetable origin and characterized by
remarkable toxicological effects. Such bases occur almost
exclusively in the dicotyledons, generally in combination with
malic, citric, tartaric or similar plant-acids. They may
be extracted by exhausting the plant-tissues with a dilute
acid, and precipitating the bases with potash, soda, lime or
magnesia. The separation of the mixed bases so obtained
is effected by repeated fractional crystallization, or by
taking advantage of certain properties of the constituents.
A chemical classification of alkaloids is difficult on
account of their complex constitution. I. A. Wyschnegradsky,
and afterwards W. Konigs, expressed the opinion that the
alkaloids were derivatives of pyridine or quinoline. This
view has been fairly well supported by later discoveries;
but, in addition to pyridine and quinoline nuclei, alkaloids
derived from isoquinoline are known. The purely chemical
literature on the alkaloids is especially voluminous;
and from the assiduity with which the constitutions of
these substances have been and are still being attacked,
we may conclude that their synthesis is but a question of
time. Piperine, conine, atropine, belladonine, cocaine,
hyoscyamine and nicotine have been already synthesized; the
constitution of several others requires confirmation, while
there remain many important alkaloids--quinine, morphine,
strychnine, &c.--whose constitution remains unknown.
The following classification is simple and convenient; the
list of alkaloids makes no pretence at being exhaustive.
(1) Pyridine group. Piperine; conine; trigonelline;
arecaidine; guvacine; pilocarpine; cytisine; nicotine;
sparteine.
(2) Tropine group. Alkaloids characterized by containing
the tropine (q.v.) nucleus. Atropine; cocaine; hygrine;
ecgonine; pelletierine.
(3) Quinoline group. The alkaloids of the quina-barks:
quinine, &c.; the strychnos bases: strychnine, brucine;
and the veratrum alkaloids: veratrine, cevadine, &c.
(4) Isoquinoline group. The opium alkaloids: morphine,
codeine, thebaine, papaverine, narcotine, narceine, &c.;
and the complicated substances hydrastine and berberine.
In addition to the above series there are a considerable number
of compounds derived from purin which are by some writers
classed with the alkaloids. These are treated in the article
PURIN. There are also reasons for including such compounds
as muscarine, choline, neurine and betaine in this group.
The greater number of these substances are of considerable
medicinal value; this aspect is treated generally in the
article PHARMACOLOGY. Reference should also be made
to the articles on the individual alkaloids for further
details as to their medicinal and chemical properties.
The chemistry of the alkaloids is treated in detail by Ame
Pictet in his La Constitution chimique des alcatoides vegetaux
(Paris, 1897); enlarged and translated by H. C. Biddle wiih
the title The Vegetable Alkaloids (New Vork, 1904); and by
J. W. Bruhl, F. HJelt, and O. Aschan: Die Pflanzen-Alkaloide
(1900). A pamphlet, Die Alkaloidchemie in den Jahren
1900-1904, by Julius Schmidt, may also be consulted.
ALKAN, CHARLES HENRI VALENTIN MORHANGE (1813-1888), French
musical composer, was born and died in Paris. Alkan was his
nom de guerre. Admitted to the Conservatoire of Paris in his
sixth year, he had a distinguished career there until 1830.
He visited London in 1833, after which he settled in Paris as
a pianoforte teacher till his death. He is important as the
composer of a large number of pianoforte etudes, embodying
the most extravagant technical difficulties. His invention
was not modern enough to secure for these works that attention
which they deserve as representing a pianoforte technique
and sense of effect in some respects more advanced even
than that of Liszt, though lacking Liszt's economy and tact.
ALKANET (dim. from Span. alcana, Arab. al-hena = henna,
Egyptian privet, or Lawsonia inermis), a plant, Alkanna or
Anchusa tinctoria, of the order Boraginaceae, also known as
orchanet, dyer's bugloss, Spanish bugloss or bugloss of Languedoc,
which is grown in the south of France and on the shores of the
Levant. Its root yields a fine red colouring matter which
has been used to tint tinctures, oils, wines, varnishes, &c.
AL KASR AL KEBIR (``the great castle,'' in Span. ALCAZAR
KEBIR, in Port. ALCACER QUBIR), a town of Morocco, on the
river Lekkus, 80 m. N.W. of Fez. Pop. about 10,000. Its mud
and pantile dwellings are here and there relieved by a mosque
tower, but the aspect of the town is far from inviting. It
is frequently flooded in winter and in consequence fever is
prevalent. The weekly market, held on Sundays in the centre
of the town, gives to the place an appearance of bustle.
A vice-governor is appointed for the town by the basha of
Laraiche, one for the country round by the sultan of Morocco,
a condition which causes much confusion on market-days. Al
Kasr al Rebir was built, according to Leo Africanus, by Yakub
el Mansur (1186-1199). Not far from the town, by the banks
of the river Makhazan, is the site of the battle fought in
1578 between Dom Sebastian, king of Portugal, and the Moors
under Abd el Malek, in which the Moors were victorious, though
both kings perished, as well as the deposed Mahommed XI., who
had called in the Portuguese to his aid against Abd el Malek.
ALKMAAR, a town in the province of North Holland, kingdom of
Holland, 24 1/2 m. by rail N.N.W. of Amsterdam, connected by
steam-tramway with Haarlem and Amsterdam, and on the North Holland
canal. Pop. (1900) 18,373. Alkmaar is a typical North Holland
town, with tree-lined canals and brightly coloured 17th-century
houses. The old city walls have been replaced by pleasant
gardens and walks, and there is a park in which stands a fine
monument (1876) by J. T. Stracke (1817- 1891), symbolizing
Alcmaria victrix, to commemorate the siege by the Spaniards in
1573. The Groote Kerk (1470-1498), dedicated to St Lawrence,
is a handsome building and contains the tomb of Floris
V., count of Holland (d. 1296), a brass of 1546, and some
paintings (1507). In the town hall (1507) are the library
and a small museum with two pictures by the 17th century
artist Caesar van Everdingen, who with his more celebrated
brother Allart van Everdingen (q.v.) was a native of the
town. The weigh-house (1582) is a picturesque building
with quaint gable and tower. Just outside the town lies the
Alkmaar wood, at the entrance to which stands the military
cadet school which serves as a preparatory school for the
royal military academy at Breda. Alkmaar derives its chief
