[1] In Arabia proper it is rarely employed in speech and never in
writing, strictly Arabic words such as _Rikb_ ("assembled riders") or
_Qafila_ ("wayfaring band") being in ordinary use.
[2] The Syrian and Egyptian haj; have been able, since 1908, to
travel by the railway from Damascus to the Hejaz.
CARAVANSERAI, a public building, for the shelter of a caravan (q.v.) and
of wayfarers generally in Asiatic Turkey. It is commonly constructed in
the neighbourhood, but not within the walls, of a town or village. It is
quadrangular in form, with a dead wall outside; this wall has small
windows high up, but in the lower parts merely a few narrow air-holes.
Inside a cloister-like arcade, surrounded by cellular store-rooms, forms
the ground floor, and a somewhat lighter arcade, giving access to little
dwelling-rooms, runs round it above. Broad open flights of stone steps
connect the storeys. The central court is open to the sky, and generally
has in its centre a well with a fountain-basin beside it. A spacious
gateway, high and wide enough to admit the passage of a loaded camel,
forms the sole entrance, which is furnished with heavy doors, and is
further guarded within by massive iron chains, drawn across at night.
The entry is paved with flagstones, and there are stone seats on each
side. The court itself is generally paved, and large enough to admit of
three or four hundred crouching camels or tethered mules; the bales of
merchandise are piled away under the lower arcade, or stored up in the
cellars behind it. The upstairs apartments are for human lodging;
cooking is usually carried on in one or more corners of the quadrangle
below. Should the caravanserai be a small one, the merchants and their
goods alone find place within, the beasts of burden being left outside.
A porter, appointed by the municipal authority of the place, is always
present, lodged just within the gate, and sometimes one or more
assistants. These form a guard of the building and of the goods and
persons in it, and have the right to maintain order and, within certain
limits, decorum; but they have no further control over the temporary
occupants of the place, which is always kept open for all arrivals from
prayer-time at early dawn till late in the evening. A small gratuity is
expected by the porter, but he has no legal claim for payment, his
maintenance being provided for out of the funds of the institution.
Neither food nor provender is supplied.
Many caravanserais in Syria, Mesopotamia and Anatolia have considerable
architectural merit; their style of construction is in general that
known as Saracenic; their massive walls are of hewn stone; their
proportions apt and grand. The portals especially are often decorated
with intricate carving; so also is the prayer-niche within. These
buildings, with their belongings, are works of charity, and are
supported, repaired and so forth out of funds derived from pious
legacies, most often of land or rentals. Sometimes a municipality takes
on itself to construct and maintain a caravanserai; but in any case the
institution is tax-free, and its revenues are inalienable. When, as
sometimes happens, those revenues have been dissipated by peculation,
neglect or change of times, the caravanserai passes through downward
stages of dilapidation to total ruin (of which only too many examples
may be seen) unless some new charity intervene to repair and renew it.
_Khans, i.e._ places analogous to inns and hotels, where not lodging
only, but often food and other necessaries or comforts may be had for
payment, are sometimes by inaccurate writers confounded with
caravanserais. They are generally to be found within the town or village
precincts, and are of much smaller dimensions than caravanserais. The
khan of Asad Pasha at Damascus is a model of constructive skill and
architectural beauty.
CARAVEL, or CARVEL (from the Gr. [Greek: k['a]rabos], a light ship,
through the Ital. _carabella_ and the Span. _carabas_), a name applied
at different times and in different countries to ships of very varying
appearance and build, as in Turkey to a ship of war, and in France to a
small boat used in the herring fishery. In the 15th and 16th centuries,
caravels were much used by the Portuguese and Spanish for long voyages.
They were roundish ships, with a double tower at the stern, and a single
one in the bows, and were galley rigged. Two out of the three vessels in
which Columbus sailed on his voyage of discovery to America were
"caravels." Carvel, the older English form, is now used only in the term
"carvel-built," for a boat in which the planking is flush with the edges
laid side to side, in distinction from "clinker-built," where the edges
overlap.
CARAVELLAS, a small seaport of southern Bahia, Brazil, on the Caravellas
river a few miles above its mouth, which is dangerously obstructed by
sandbars. Pop. (1890) of the municipality 5482, about one-half of whom
lived in the town. Caravellas was once the centre of a flourishing whale
fishery, but has since fallen into decay. It is the port of the Bahia &
Minas railway, whose traffic is comparatively unimportant.
CARAWAY, the fruit, or so-called seed, of _Carum Carui_, an
umbelliferous plant growing throughout the northern and central parts of
Europe and Asia, and naturalized in waste places in England. The plant
has finely-cut leaves and compound umbels of small white flowers. The
fruits are laterally compressed and ovate, the mericarps (the two
portions into which the ripe fruit splits) being subcylindrical,
slightly arched, and marked with five distinct pale ridges. Caraways
evolve a pleasant aromatic odour when bruised, and they have an
agreeable spicy taste. They yield from 3 to 6% of a volatile oil, the
chief constituent of which is cymene aldehyde. Cymene itself is present,
having the formula CH3C6H4CH(CH3)2; also carvone C10H14O, and limonene,
a terpene. The dose of the oil is 1/2-3 minims. The plant is cultivated
in north and central Europe, and Morocco, as well as in the south of
England, the produce of more northerly latitudes being richer in
essential oil than that grown in southern regions. The essential oil is
largely obtained by distillation for use in medicine as an aromatic
stimulant and carminative, and as a flavouring material in cookery and
in liqueurs for drinking. Caraways are, however, more extensively
consumed entire in certain kinds of cheese, cakes and bread, and they
form the basis of a popular article of confectionery known as caraway
comfits.
CARBALLO, a town of north-western Spain, in the province of Corunna; on
the right bank of the river Allones, 20 m. S.W. of the city of Corunna.
Pop. (1900) 13,032. Carballo is the central market of a thriving
agricultural district. At San Juan de Carballo, on the opposite bank of
the Allones, there are hot sulphurous springs.
CARBAZOL, C12H9N, a chemical constituent of coal-tar and crude
anthracene. From the latter it may be obtained by fusion with caustic
potash when it is converted into carbazol-potassium, which can be easily
separated by distilling off the anthracene. It may be prepared
synthetically by passing the vapours of diphenylamine or aniline through
a red-hot tube; by heating diorthodiaminodiphenyl with 25% sulphuric
acid to 200 deg. C. for 15 hours; by heating orthoaminodiphenyl with
lime; or by heating thiodiphenylamine with copper powder. It is also
obtained as a decomposition product of brucine or strychnine, when these
alkaloids are distilled with zinc dust. It is easily soluble in the
common organic solvents, and crystallizes in plates or tables melting at
238 deg. C. It is a very stable compound, possessing feebly basic
properties and characterized by its ready sublimation. It distils
unchanged, even when the operation is carried out in the presence of
zinc dust. On being heated with caustic potash in a current of carbonic
acid, it gives carbazol carbonic acid C12H8N.COOH; melted with oxalic
acid it gives carbazol blue. It dissolves in concentrated sulphuric acid
to a clear yellow solution. The potassium salt reacts with the alkyl
iodides to give N-substituted alkyl derivatives. It gives the
pine-shaving reaction, in this respect resembling pyrrol (q.v.).
CARBIDE, in chemistry, a compound of carbon with another element. The
introduction of the electric furnace into practical chemistry was
followed by the preparation of many metallic carbides previously
unknown, some of which, especially calcium carbide, are now of great
commercial importance. Carbides of the following general formulae have
been obtained by H. Moissan (M denotes an atom of metal and C of
carbon):--
M3C = manganese, iron; M2C = molybdenum; M3C2 = chromium; MC =
zirconium; M4C3 = beryllium, aluminium; M2C3 = uranium; MC2 = barium,
calcium, strontium, lithium, thorium, &c.; MC4 = chromium.
The principal methods for the preparation of carbides may be classified
as follows:--(1) direct union at a high temperature, e.g. lithium, iron,
chromium, tungsten, &c.; (2) by the reduction of oxides with carbon at
high temperatures, e.g. calcium, barium, strontium, manganese, chromium,
&c.; (3) by the reduction of carbonates with magnesium in the presence
of carbon, e.g. calcium, lithium; (4) by the action of metals on
acetylene or metallic derivatives of acetylene, e.g., sodium, potassium.
The metallic carbides are crystalline solids, the greater number being
decomposed by water into a metallic hydrate and a hydrocarbon; sometimes
hydrogen is also evolved. Calcium carbide owes its industrial importance
to its decomposition into acetylene; lithium carbide behaves similarly.
Methane is yielded by aluminium and beryllium carbides, and, mixed with
hydrogen, by manganese carbide. The important carbides are mentioned in
the separate articles on the various metals. The commercial aspect of
calcium carbide is treated in the article ACETYLENE.
CARBINE (Fr. _carabine_, Ger. _Karabiner_), a word which came into use
towards the end of the 16th century to denote a form of small fire-arm,
shorter than the musket and chiefly used by mounted men. It has retained
this significance, through all subsequent modifications of small-arm
design, to the present day, and is now as a rule a shortened and
otherwise slightly modified form of the ordinary rifle (q.v.).
CARBO, the name of a Roman plebeian family of the gens Papiria. The
following are the most important members in Roman history:--
1. GAIUS PAPIRIUS CARBO, statesman and orator. He was associated with C.
Gracchus in carrying out the provisions of the agrarian law of Tiberius
Gracchus (see GRACCHUS). When tribune of the people (131 B.C.) he
carried a law extending voting by ballot to the enactment and repeal of
laws; another proposal, that the tribunes should be allowed to become
candidates for the same office in the year immediately following, was
defeated by the younger Scipio Africanus. Carbo was suspected of having
been concerned in the sudden death of Scipio (129), if not his actual
murderer. He subsequently went over to the optimates, and (when consul
in 120) successfully defended Lucius Opimius, the murderer of Gaius
Gracchus, when he was impeached for the murder of citizens without a
trial, and even went so far as to say that Gracchus had been justly
slain. But the optimates did not trust Carbo. He was impeached by
Licinius Crassus on a similar charge, and, feeling that he had nothing
to hope for from the optimates and that his condemnation was certain, he
committed suicide.
See Livy, _Epit._ 59; Appian, _Bell. Civ._ i. 18: Vell. Pat. ii. 4;
Val. Max. iii. 7. 6; A.H.J. Greenidge, _History of Rome_ (1904).
2. His son, GAIUS PAPIRIUS CARBO, surnamed Arvina, was a staunch
supporter of the aristocracy, and was put to death by the Marian party
in 82. He is known chiefly for the law (Plautia Papiria) carried by him
and M. Plautius Silvanus when tribunes of the people in 90 (or 89),
whereby the Roman franchise was offered to every Italian ally domiciled
in Italy at the time when the law was enacted, provided he made
application personally within sixty days to the praetor at Rome (see
ROME: _History_, II. "The Republic," Period C.). The object of the law
was to conciliate the states at war with Rome and to secure the loyalty
of the federate states. Like his father, Carbo was an orator of
distinction.
See Cicero, _Pro Archia_, 4; Vell. Pat. ii. 26; Appian, _Bell. Civ._
i. 88.
3. GNAEUS PAPIRIUS CARBO (c. 130-82 B.C.), nephew of (1). He was a
strong supporter of the Marian party, and took part in the blockade of
Rome (87). In 85 he was chosen by Cinna as his colleague in the
consulship, and extensive preparations were made for carrying on war in
Greece against Sulla, who had announced his intention of returning to
Italy. Cinna and Carbo declared themselves consuls for the following
year, and large bodies of troops were transported across the Adriatic;
but when Cinna was murdered by his own soldiers, who refused to engage
in civil war, Carbo was obliged to bring them back. In 82 Carbo, then
consul for the third time with the younger Marius, fought an indecisive
engagement with Sulla near Clusium, but was defeated with great loss in
an attack on the camp of Sulla's general, Q. Caecilius Metellus Pius
[see under METELLUS (6)] near Faventia. Although he still had a large
army and the Samnites remained faithful to him, Carbo was so
disheartened by his failure to relieve Praeneste, where the younger
Marius had taken refuge, that he decided to leave Italy. He first fled
to Africa, thence to the island of Cossyra (Pentellaria), where he was
arrested, taken in chains before Pompey at Lilybaeum and put to death.
See Appian, _Bell. Civ._ i. 67-98; Livy, _Epit._ 79, 84, 88, 89;
Plutarch, _Pompey_, 5, 6, 10, and _Sulla_, 28; Cicero, _ad Fam._ ix.
21; Eutropius, v. 8, 9; Orosius, v. 20; Valerius Maximus, v. 3. 5, ix.
13. 2; art. SULLA, L. CORNELIUS.
CARBOHYDRATE, in chemistry, the generic name for compounds empirically
represented by the formula C_{x}(H2O)_{y}. They are essentially
vegetable products, and include the sugars, starches, gums and
celluloses (q.v.).
CARBOLIC ACID or PHENOL (hydroxy-benzene), C6H5OH, an acid found in the
urine of the herbivorae, and in small quantity in _castoreum_ (F.
Wohler, _Ann._, 1848, 67, p. 360). Its principal commercial source is
the fraction of coal-tar which distils between 150 and 200 deg. C., in
which it was discovered in 1834 by F. Runge. In order to obtain the
phenol from this distillate, it is treated with caustic soda, which
dissolves the phenol and its homologues together with a certain quantity
of naphthalene and other hydrocarbons. The solution is diluted with
water, and the hydrocarbons are thereby precipitated and separated. The
solution is then acidified, and the phenols are liberated and form an
oily layer on the surface of the acid. This layer is separated, and the
phenol recovered by a process of fractional distillation. It may be
synthetically prepared by fusing potassium benzene sulphonate with
caustic alkalis (A. Kekule, A. Wurtz); by the action of nitrous acid on
aniline; by passing oxygen into boiling benzene containing aluminium
chloride (C. Friedel and J.M. Crafts, _Ann. Chim. Phys._, 1888 (6) 14,
p. 435); by heating phenol carboxylic acids with baryta; and, in small
quantities by the oxidation of benzene with hydrogen peroxide or nascent
ozone (A.R. Leeds, _Ber._, 1881, 14, p. 976).
It crystallizes in rhombic needles, which melt at 42.5-43 deg. C., and
boil at 182-183 deg. C.; its specific gravity is 1.0906 (0 deg. C.). It
has a characteristic smell, and a biting taste; it is poisonous, and
acts as a powerful antiseptic. It dissolves in water, 15 parts of water
dissolving about one part of phenol at 16-17 deg. C., but it is miscible
in all proportions at about 70 deg. C.; it is volatile in steam, and is
readily soluble in alcohol, ether, benzene, carbon bisulphide,
chloroform and glacial acetic acid. It is also readily soluble in
solutions of the caustic alkalis, slightly soluble in aqueous ammonia
solution, and almost insoluble in sodium carbonate solution. When
exposed in the moist condition to the air it gradually acquires a red
colour. With ferric chloride it gives a violet coloration, and with
bromine water a white precipitate of tribrom-phenol.
When phenol is passed through a red-hot tube a complex decomposition
takes place, resulting in the formation of benzene, toluene,
naphthalene, &c. (J.G. Kramers, _Ann._, 1877, 189, p. 129). Chromium
oxychloride reacts violently on phenol, producing hydroquinone ether,
O(C6H4OH)2; chromic acid gives phenoquinone, and potassium
permanganate gives paradiphenol, oxalic acid, and some salicylic acid
(R. Henriques, _Ber._, 1888, 21, p. 1620). In alkaline solution,
potassium permanganate oxidizes it to inactive tartaric acid and
carbon dioxide (O. Doebner, _Ber._, 1891, 24, p. 1755). When distilled
over lead oxide, it forms diphenylene oxide, (C6H4)2O; and when
heated with oxalic acid and concentrated sulphuric acid, it forms
aurin, C19H14O3. It condenses with aceto-acetic ester, in the presence
of sulphuric acid, to [beta]-methyl coumarin (H. v. Pechmann and J.B.
Cohen, _Ber_., 1884, 17, p. 2188).
The hydrogen of the hydroxyl group in phenol can be replaced by
metals, by alkyl groups and by acid radicals. The metallic derivatives
(phenolates, phenates or carbolates) of the alkali metals are obtained
by dissolving phenol in a solution of a caustic alkali, in the absence
of air. Potassium phenolate, C6H5OK, crystallizes in fine needles, is
very hygroscopic and oxidizes rapidly on exposure. Other phenolates
may be obtained from potassium phenolate by precipitation. The alkyl
derivatives may be obtained by heating phenol with one molecular
proportion of a caustic alkali and of an alkyl iodide. They are
compounds which greatly resemble the mixed ethers of the aliphatic
series. They are not decomposed by boiling alkalis, but on heating
with hydriodic acid they split into their components. _Anisol_, phenyl
methyl ether, C6H5.O.CH3, is prepared either by the above method or by
the action of diazo-methane on phenol, C6H5OH+CH2N2 = N2+C6H5.O.CH3
(H. v. Pechmann, _Ber_., 1895, 28, p. 857); by distilling anisic acid
(para-methoxy benzoic acid) with baryta or by boiling phenyl diazonium
chloride with methyl alcohol. It is a colourless pleasant-smelling
liquid which boils at 154.3 deg. C. _Phenetol_, phenyl ethyl ether,
C6H5.O.C2H5, a liquid boiling at 172 deg. C., may be obtained by
similar methods. A. Hantzsch (_Ber._, 1901, 34, p. 3337) has shown
that in the action of alcohols on diazonium salts an increase in the
molecular weight of the alcohol and an accumulation of negative groups
in the aromatic nucleus lead to a diminution in the yield of the ether
produced and to the production of a secondary reaction, resulting in
the formation of a certain amount of an aromatic hydrocarbon.
The acid esters of phenol are best obtained by the action of acid
chlorides or anhydrides on phenol or its sodium or potassium salt, or
by digesting phenol with an acid in the presence of phosphorus
oxychloride (F. Rasinski, _Jour. f. prak. Chem._, 1882 [2], 26, p.
62). Phenyl acetate, C6H5.O.COCH3, a colourless liquid of boiling
point 193 deg. C., may be prepared by heating phenol with acetamide.
When heated with aniline it yields phenol and acetanilide. Phenyl
benzoate, C6H5.O.COC5H5, prepared from phenol and benzoyl chloride,
crystallizes in monoclinic prisms, which melt at 68-69 deg. C. and
boil at 314 deg. C.
Phenol is characterized by the readiness with which it forms
substitution products; chlorine and bromine, for example, react
readily with phenol, forming ortho- and para- chlor- and -bromphenol,
and, by further action, trichlor- and tribrom-phenol. Iodphenol is
obtained by the action of iodine and iodic acid on phenol dissolved in
a dilute solution of caustic potash. Nitro-phenols are readily
obtained by the action of nitric acid on phenol. By the action of
dilute nitric acid, ortho- and para-nitrophenols are obtained, the
ortho-compound being separated from the para-compound by distillation
in a current of steam. Ortho-nitrophenol, C6H4.OH.NO2(1.2),
crystallizes in yellow needles which melt at 45 deg. C. and boil at
214 deg.C. Para-nitrophenol, C6H4.OH.NO2(1.4), crystallizes in long
colourless needles which melt at 114 deg.C. Meta-nitrophenol,
C6H4.OH.NO2.(1.3), is prepared from meta-nitraniline by diazotizing
the base and boiling the resulting diazonium salt with water. By
nitrating phenol with concentrated nitric acid, no care being taken to
keep the temperature of reaction down, trinitrophenol (picric acid) is
obtained (see PICRIC ACID). By the reduction of nitro-phenols, the
corresponding aminophenols are obtained, and of these, the meta- and
para-derivatives are the most important. Para-aminophenol,
C6H4.OH.NH2(1.4) melts at 148 deg. C., with decomposition. Its most
important derivative is phenacetin. Meta-aminophenol,
C6H4.OH.NH2(1.3), and dimethyl meta-aminophenol, C6H4.OH.N(CH3)2(1.3),
are extensively employed in the manufacture of the important dyestuffs
known as the rhodamines. The aminophenols also find application as
developers in photography, the more important of these developers
being amidol, the hydrochloride of diaminophenol, ortol, the
hydrochloride of para-methylaminophenol, C6H4.OH.NHCH3.HCl(1.4),
rodinal, para-aminophenol, and metol, the sulphate of a
methylaminophenol sulphonic acid. Meta-aminophenol is prepared by
reducing meta-nitrophenol, or by heating resorcin with ammonium
chloride and ammonia to 200 deg. C. Dimethyl-meta-aminophenol is
prepared by heating meta-aminophenol with methyl alcohol and
hydrochloric acid in an autoclave; by sulphonation of dimethylaniline,
the sulphonic acid formed being finally fused with potash; or by
nitrating dimethylaniline, in the presence of sulphuric, acid at 0
deg. C. In the latter case a mixture of nitro-compounds is obtained
which can be separated by the addition of sodium carbonate. The
meta-nitro-compound, which is precipitated last, is then reduced, and
the amino group so formed is replaced by the hydroxyl group by means
of the Sandmeyer reaction. Dimethyl-meta-aminophenol crystallizes in
small prisms which melt at 87 deg. C. It condenses with phthalic
anhydride to form rhodamine, and with succinic anhydride to rhodamine
S.
Phenol dissolves readily in concentrated sulphuric acid, a mixture of
phenol-ortho- and -para-sulphonic acids being formed. These acids may
be separated by conversion into their potassium salts, which are then
fractionally crystallized, the potassium salt of the para-acid
separating first. The ortho-acid, in the form of its aqueous solution,
is sometimes used as an antiseptic, under the name of aseptol. A
_thiophenol_, C6H5SH, is known, and is prepared by the action of
phosphorus pentasulphide on phenol, or by distilling a mixture of
sodium benzene sulphonate and potassium sulphydrate. It is a
colourless liquid, which possesses a very disagreeable smell, and
boils at 168 deg. C.
Various methods have been devised for the quantitative determination
of phenol. J. Messinger and G. Vortmann (_Ber._, 1890, 23, p. 2753)
dissolve phenol in caustic alkali, make the solution up to known
volume, take an aliquot part, warm it to 60 deg. C., and add
decinormal iodine solution until the liquid is of a deep yellow
colour. The mixture is then cooled, acidified by means of sulphuric
acid, and titrated with decinormal sodium thiosulphate solution. S.B.
Schryver (_Jour, of Soc. Chem. Industry_, 1899, 18, p. 553) adds
excess of sodamide to a solution of the phenol in a suitable solvent,
absorbs the liberated ammonia in an excess of acid, and titrates the
excess of acid. See also C.E. Smith, _Amer. Jour. Pharm._, 1898, 369.
_Pharmacology and Therapeutics_.--Carbolic acid is an efficient
parasiticide, and is largely used in destroying the fungus of ringworm
and of the skin disease known as _pityriasis versicolor_. When a
solution of the strength of about 1 in 20 is applied to the skin it
produces a local anaesthesia which lasts for many hours. If
concentrated, however, it acts as a caustic. It never produces
vesication. The drug is absorbed through the unbroken skin--a very
valuable property in the treatment of such conditions as an incipient
whitlow. A piece of cotton wool soaked in strong carbolic acid will
relieve the pain of dental caries, but is useless in other forms of
toothache. Taken internally, in doses of from one to three grains,
carbolic acid will often relieve obstinate cases of vomiting and has
some value as a gastric antiseptic.
_Toxicology_.--Carbolic acid is distinguished from all other acids
so-called--except oxalic acid and hydrocyanic acid--in that it is a
neurotic poison, having a marked action directly upon the nervous
system. In all cases of carbolic acid poisoning the nervous influence is
seen. If it be absorbed from a surgical dressing there are no irritant
symptoms, but when the acid is swallowed in concentrated form, symptoms
of gastro-intestinal irritation occur. The patient becomes collapsed,
and the skin is cold and clammy. The breathing becomes shallow, the drug
killing, like nearly all neurotic poisons (alcohol, morphia, prussic
acid, &c.), by paralysis of the respiratory centre, and the patient
dying in a state of coma. The condition of the urine is of the utmost
importance, as it is often a clue to the diagnosis, and in surgical
cases may be the first warning that absorption is occurring to an undue
degree. The urine becomes dark green in colour owing to the formation of
various oxidation products such as pyrocatechin. Fifteen grains
constitute an exceedingly dangerous dose for an adult male of average
weight. Other symptoms of undue absorption are vertigo, deafness, sounds
in the ears, stupefaction, a subnormal temperature, nausea, vomiting and
a weak pulse (Sir Thomas Fraser).
The antidote in cases of carbolic acid poisoning is any soluble
sulphate. Carbolic acid and sulphates combine in the blood to form
sulpho-carbolates, which are innocuous. The symptoms of nerve-poisoning
are due to the carbolic acid (or its salts) which circulate in the blood
after all the sulphates in the blood have been used up in the formation
of sulpho-carbolates (hence, during administration of carbolic acid, the
urine should frequently be tested for the presence of free sulphates; as
long as these occur in the urine, they are present in the blood and
there is no danger). The treatment is therefore to administer an ounce
of sodium sulphate in water by the mouth, or to inject a similar
quantity of the salt in solution directly into a vein or into the
subcutaneous tissues. Magnesium sulphate may be given by the mouth, but
is poisonous if injected intravenously. If the acid has been swallowed,
wash out the stomach and give chalk, the carbolate of calcium being
insoluble. Alkalis which form soluble carbolates are useless. Give ether
and brandy subcutaneously and apply hot water-bottles and blankets if
there are signs of collapse.
CARBON (symbol C, atomic weight 12), one of the chemical non-metallic
elements. It is found native as the diamond (q.v.), graphite (q.v.), as
a constituent of all animal and vegetable tissues and of coal and
petroleum. It also enters (as carbonates) into the composition of many
minerals, such as chalk, dolomite, calcite, witherite, calamine and
spathic iron ore. In combination with oxygen (as carbon dioxide) it is
also found to a small extent in the atmosphere. It is a solid substance
which occurs in several modifications, differing very much in their
physical properties. _Amorphous carbon_ is obtained by the destructive
distillation of many carbon compounds, the various kinds differing very
greatly as regards physical characters and purity, according to the
substance used for their preparation. The most common varieties met with
are lampblack, gas carbon, wood charcoal, animal charcoal and coke.
_Lampblack_ is prepared by burning tar, resin, turpentine and other
substances rich in carbon, with a limited supply of air; the products of
combustion being conducted into condensing chambers in which cloths are
suspended, on which the carbon collects. It is further purified by
heating in closed vessels, but even then it still contains a certain
amount of mineral matter and more or less hydrocarbons. It is used in
the manufacture of printer's ink, in the preparation of black paint and
in calico printing. _Gas carbon_ is produced by the destructive
distillation of coal in the manufacture of illuminating gas (see GAS:
_Manufacture_), being probably formed by the decomposition of gaseous
hydrocarbons. It is a very dense form of carbon, and is a good conductor
of heat and electricity. It is used in the manufacture of carbon rods
for arc lights, and for the negative element in the Bunsen battery.
_Charcoal_ is a porous form of carbon; several varieties exist. _Sugar
charcoal_ is obtained by the carbonization of sugar. It is purified by
boiling with acids, to remove any mineral matter, and is then ignited
for a long time in a current of chlorine in order to remove the last
traces of hydrogen. _Animal charcoal_ (bone black) is prepared by
charring bones in iron retorts. It is a very impure form of carbon,
containing on the average about 80% of calcium phosphate. It possesses a
much greater decolorizing and absorbing power than wood charcoal. A
variety of animal charcoal is sometimes prepared by calcining fresh
blood with potassium carbonate in large cylinders, the mass being
purified by boiling out with dilute hydrochloric acid and subsequent
reheating. _Wood charcoal_ is a hard and brittle black substance, which
retains the external structure of the wood from which it is made. It is
prepared (where wood is plentiful) by stacking the wood in heaps, which
are covered with earth or with brushwood and turf, and then burning the
heap slowly in a limited supply of air. The combustion of the wood is
conducted from the top downwards, and from the exterior towards the
centre; great care has to be taken that the process is carried out
slowly. The disadvantage in this process is that the by-products, such
as pyroligneous acid, acetone, wood spirit, &c., are lost; as an
alternative method, wood is frequently carbonized in ovens or retorts
and the volatile products are condensed and utilized.
Charcoal varies considerably in its properties, depending upon the
particular variety of wood from which it is prepared, and also upon
the process used in its manufacture. It can be made at a temperature
as low as 300 deg. C., and is then a soft, very friable material
possessing a low ignition point. When made at higher temperatures it
is much more dense, and its ignition point is considerably higher.
Charcoal burns when heated in air, usually without the formation of
flame, although a flame is apparent if the temperature be raised. It
is characterized by its power of absorbing gases; thus, according to
J. Hunter [_Phil. Mag._, 1863 (4), 25, p. 363], one volume of charcoal
absorbs (at 0 deg. C. and 760 mm. pressure) 171.7 ccs. of ammonia,
86.3 ccs. of nitrous oxide, 67.7 ccs. of carbon monoxide, 21.2 ccs. of
carbon dioxide, 17.9 ccs. of oxygen, 15.2 ccs. of nitrogen, and 4.4
ccs. of hydrogen [see also J. Dewar, _Ann. Chim. Phys._, 1904 (8), 3,
p. 5]. It also has the power of absorbing colouring matters from
solution. Charcoal is used as a fuel and as a reducing agent in
metallurgical processes.
The element carbon unites directly with hydrogen to form acetylene
when an electric arc is passed between carbon poles in an atmosphere
of hydrogen (M. Berthelot); it also unites directly with fluorine,
producing, chiefly, carbon tetrafluoride CF4. It burns when heated in
an atmosphere of oxygen, forming carbon dioxide, and when heated in
sulphur vapour it forms carbon bisulphide (q.v.). When heated with
nitrogenous substances, in the presence of carbonated or caustic
alkali, it forms cyanides. It combines directly with silicon, at the
temperature of the electric furnace, yielding _carborundum_, SiC; and
H. Moissan has also shown that it will combine with many metals at
the temperature of the electric furnace, to form carbides (q.v.).
The specific heat of carbon varies with the temperature the following
values having been obtained by H.F. Weber (_Jahresberichte_, 1874, p.
63):--
+-----------------+-----------------+-------------------+
| Diamond. | Graphite. |Porous wood carbon.|
+-------+---------+-------+---------+--------+----------+
| t deg.| Sp. Ht. | t deg.| Sp. Ht. | t deg. | Sp. Ht. |
+-------+---------+-------+---------+--------+----------+
| -50.5 | 0.0635 | -50.3 | 0.1138 | 0-23 | 0.1653 |
| -10.6 | 0.0955 | -10.7 | 0.1437 | 0-99 | 0.1935 |
| +10.7 | 0.1128 | +10.8 | 0.1604 | 0-223 | 0-2385 |
| 85.5 | 0.1765 | 61.3 | 0.1990 | | |
| 206.1 | 0.2733 | 201.6 | 0.2966 | | |
| 606.7 | 0.4408 | 641.9 | 0.4454 | | |
| 985.0 | 0.4589 | 977.0 | 0.4670 | | |
+-------+---------+-------+---------+--------+----------+
The atomic weight of carbon has been determined by J.B.A. Dumas and by
J.S. Stas [_Ann. Chim. Phys._, 1841 (3), 1, p. 1: _Jahresb._, 1849,
223] by estimating the amount of carbon dioxide formed on burning
graphite or diamond in a current of oxygen, the value obtained being
12.0 (O = 16). Confirmatory evidence has also been obtained by O.L.
Erdmann and R.F. Marchand (_Jour. Prak. Chem._, 1841, 23, p. 159; see
also F.W. Clarke, _Jahresb._, 1881, p. 7).
_Compounds_.--Three oxides of carbon are known, namely, carbon
suboxide, C3O2, carbon monoxide, CO, and carbon dioxide, CO2. _Carbon
suboxide_, C3O2, is formed by the action of phosphorus pentoxide on
ethyl malonate (O. Diels and B. Wolf, _Ber._, 1906, 39, p. 689),
CH2(COOC2H5)2 = 2C2H4 + 2H2O + C3O2. At ordinary temperatures it is a
colourless gas, possessing a penetrating and suffocating smell. It
liquefies at 7 deg. C. It is an exceedingly reactive compound,
combining with water to form malonic acid, with hydrogen chloride to
form malonyl chloride, and with ammonia to form malonamide. When kept
for some time in sealed tubes it changes to a yellowish liquid, from
which a yellow flocculent substance gradually separates, and finally
it suddenly solidifies to a dark red mass, which appears to be a
polymeric form. Its vapour density agrees with the molecular formula
C3O2, and this formula is also confirmed by exploding the gas with
oxygen and measuring the amount of carbon dioxide produced (see
KETENES).
_Carbon monoxide_, CO, is found to some extent in volcanic gases. It
was first prepared in 1776 by J.M.F. Lassone (_Mem. Acad. Paris_) by
heating zinc oxide with carbon, and was for some time considered to be
identical with hydrogen. Cruikshank concluded that it was an oxide of
carbon, a fact which was confirmed by Clement and J.B. Desormes (_Ann.
Chim. Phys._, 1801, 38, p. 285). It may be prepared by passing carbon
dioxide over red-hot carbon, or red-hot iron; by heating carbonates
(magnesite, chalk, &c.) with zinc dust or iron; or by heating many
metallic oxides with carbon. It may also be prepared by heating formic
and oxalic acids (or their salts) with concentrated sulphuric acid (in
the case of oxalic acid, an equal volume of carbon dioxide is
produced); and by heating potassium ferrocyanide with a large excess
of concentrated sulphuric acid, K4Fe(CN)6 + 6H2SO4 + 6H2O = 2K2SO4 +
FeSO4 + 3(NH4)2SO4 + 6CO. It is a colourless, odourless gas of
specific gravity 0.967 (air = 1). It is one of the most difficultly
liquefiable gases, its critical temperature being -139.5 deg. C., and
its critical pressure 35.5 atmos. The liquid boils at -190 deg. C.,
and solidifies at -211 deg.C. (L.P. Cailletet, _Comptes rendus_, 1884,
99, p. 706). It is only very slightly soluble in water. It burns with
a characteristic pale blue flame to form carbon dioxide. It is very
poisonous, uniting with the haemoglobin of the blood to form
carbonyl-haemoglobin. It is a powerful reducing agent, especially at
high temperatures. It is rapidly absorbed by an ammoniacal or acid
(hydrochloric acid) solution of cuprous chloride. It unites directly
with chlorine, forming carbonyl chloride or phosgene (see below), and
with nickel and iron to form nickel and iron carbonyls (see NICKEL and
IRON). It also combines directly with potassium hydride to form
potassium formate (see FORMIC ACID). The volume composition of carbon
monoxide is established by exploding a mixture of the gas with oxygen,
two volumes of the gas combining with one volume of oxygen to form two
volumes of carbon dioxide. This fact, coupled with the determination
of the vapour density of the gas, establishes the molecular formula
CO.
_Carbon dioxide_, CO2, is a gas first distinguished from air by van
Helmont (1577-1644), who observed that it was formed in fermentation
processes and during combustion, and gave to it the name _gas
sylvestre_. J. Black (_Edin. Phys. and Lit. Essays_, 1755) showed that
it was a constituent of the carbonated alkalis and called it "fixed
air." T.O. Bergman, in 1774, pointed out its acid character, and A.L.
Lavoisier (1781-1788) first proved it to be an oxide of carbon by
burning carbon in the oxygen obtained from the decomposition of
mercuric oxide. It is a regular constituent of the atmosphere, and is
found in many spring waters and in volcanic gases; it also occurs in
the uncombined condition at the Grotto del Cane (Naples) and in the
Poison Valley (Java). It is a constituent of the minerals cerussite,
malachite, azurite, spathic iron ore, calamine, strontianite,
witherite, calcite aragonite, limestone, &c. It may be prepared by
burning carbon in excess of air or oxygen, by the direct decomposition
of many carbonates by heat, and by the decomposition of carbonates
with mineral acids, M2CO8 + 2HCl = 2MCl + H2O + CO2. It is also
formed in ordinary fermentation processes, in the combustion of all
carbon compounds (oil, gas, candles, coal, &c.), and in the process of
respiration.
It is a colourless gas, possessing a faint pungent smell and a
slightly acid taste. It does not burn, and does not support ordinary
combustion, but the alkali metals and magnesium, if strongly heated,
will continue to burn in the gas with formation of oxides and
liberation of carbon. Its specific gravity is 1.529 (air = 1). It is
readily condensed, passing into the liquid condition at 0 deg. C.
under a pressure of 35 atmospheres. Its critical temperature is 31.35
deg. C., and its critical pressure is 72.9 atmos. The liquid boils at
-78.2 deg. C. (l atmo.), and by rapid evaporation can be made to
solidify to a snow-white solid which melts at -65 deg. C.(see LIQUID
GASES). Carbon dioxide is moderately soluble in water, its coefficient
of solubility at 0 deg. C. being 1.7977 (R. Bunsen). It is still more
soluble in alcohol. The solution of the gas in water shows a faintly
acid reaction and is supposed to contain _carbonic acid_, H2CO3. The
gas is rapidly absorbed by solutions of the caustic alkalis, with the
production of alkaline carbonates (q.v.), and it combines readily with
potassium hydride to form potassium formate. It unites directly with
ammonia gas to form ammonium carbamate, NH2COONH4. It may be readily
recognized by the white precipitate which it forms when passed through
lime or baryta water. Carbon dioxide dissociates, when strongly
heated, into carbon monoxide and oxygen, the reaction being a balanced
action; the extent of dissociation for varying temperatures and
pressures has been calculated by H. Le Chateller (_Zeit. Phys. Chem._,
1888, 2, p. 782; see H. Sainte-Claire Deville, _Comptes rendus_, 1863,
56, p. 195 et seq.). The volume composition of carbon dioxide is
determined by burning carbon in oxygen, when it is found that the
volume of carbon dioxide formed is the same as that of the oxygen
required for its production, hence carbon dioxide contains its own
volume of oxygen. Carbon dioxide finds industrial application in the
preparation of soda by the Solvay process, in the sugar industry, in
the manufacture of mineral waters, and in the artificial production of
ice.
_Carbonyl chloride_ (phosgene), COCl2, was first obtained by John Davy
(_Phil. Trans._, 1812, 40, p. 220). It may be prepared by the direct
union of carbon monoxide and chlorine in sunlight (Th. Wilm and G.
Wischin, _Ann_., 1868, 14, p. 150); by the action of phosphorus
pentoxide on carbon tetrachloride at 200-210 deg. C. (G. Gustavson,
_Ber_., 1872, 5, p. 30), 4CCl4 + P4O10 = 2CO2 + 4POCl3 + 2COCl2; by
the oxidation of chloroform with chromic acid mixture (A. Emmerling
and B. Lengyel, _Ber_., 1869, 2, p. 54), 4CHCl3 + 3O2 = 4COCl2 + 2H2O
+ 2Cl2; or most conveniently by heating carbon tetrachloride with
fuming sulphuric acid (H. Erdmann, _Ber_., 1893, 26, p. 1993), 2SO3 +
CCl4 = S2O5Cl2 + COCl2.
It is a colourless gas, possessing an unpleasant pungent smell. Its
vapour density is 3.46 (air = 1). It may be condensed to a liquid,
which boils at 8 deg. C. It is readily soluble in benzene, glacial
acetic acid, and in many hydrocarbons. Water decomposes it violently,
with formation of carbon dioxide and hydrochloric acid. It reacts with
alcohol to form chlorcarbonic ester and ultimately diethyl carbonate
(see CARBONATES), and with ammonia it yields urea (q.v.). It is
employed commercially in the production of colouring matters (see
BENZOPHENONE), and for various synthetic processes.
_Carbon oxysulphide_, COS, was first prepared by C. Than in 1867
(_Ann. Suppl._, 5, p. 236) by passing carbon monoxide and sulphur
vapour through a tube at a moderate heat. It is also formed by the
action of sulphuretted hydrogen on the isocyanic esters, 2CONC2H5 +
H2S = COS + CO(NHC2H5)2, by the action of concentrated sulphuric acid
on the isothiocyanic esters, RNCS + H2O = COS + RNH2, or of dilute
sulphuric acid on the thiocyanates. In the latter reaction various
other compounds, such as carbon dioxide, carbon bisulphide and
hydrocyanic acid, are produced. They are removed by passing the
vapours in succession through concentrated solutions of the caustic
alkalis, concentrated sulphuric acid, and triethyl phosphine; the
residual gas is then purified by liquefaction (W. Hempel, _Zeit.
angew. Chemie_, 1901, 14, p. 865). It is also formed when sulphur
trioxide reacts with carbon bisulphide at 100 deg. C., CS2 + 3SO3 =
COS + 4SO2, and by the decomposition of ethyl potassium thiocarbonate
with hydrochloric acid, CO(OC2H5)SK + HCl = COS + KCl + C2H5OH. It is
a colourless, odourless gas, which burns with a blue flame and is
decomposed by heat. Its vapour density is 2.1046 (air = 1). The
liquefied gas boils at -47 deg. C. under atmospheric pressure. It is
soluble in water; the aqueous solution gradually decomposes on
standing, forming carbon dioxide and sulphuretted hydrogen. It is
easily soluble in solutions of the caustic alkalis, provided they are
not too concentrated, forming solutions of alkaline carbonates and
sulphides, COS + 4KHO = K2CO3 + K2S + 2H2O.
CARBONADO, a name given in Brazil to a dark massive form of impure
diamond, known also as "carbonate" and in trade simply as carbon. It is
sometimes called black diamond. Generally it is found in small masses of
irregular polyhedral form, black, brown or dark-grey in colour, with a
dull resinoid lustre; and breaking with a granular fracture, paler in
colour, and in some cases much resembling that of fine-grained steel.
Being slightly cellular, its specific gravity is rather less than that
of crystallized diamond. It is found almost exclusively in the state of
Bahia in Brazil, where it occurs in the _cascalho_ or diamond-bearing
gravel. Borneo also yields it in small quantity. Formerly of little or
no value, it came into use on the introduction of Leschot's
diamond-drills, and is now extremely valuable for mounting in the steel
crowns used for diamond-boring. Having no cleavage, the carbon is less
liable to fracture on the rotation of the drill than is crystallized
diamond. The largest piece of carbonado ever recorded was found in Bahia
in 1895, and weighed 3150 carats. Pieces of large size are, however,
relatively less valuable than those of moderate dimensions, since they
require the expenditure of much labour in reducing them to fragments of
a suitable size for mounting in the drill-heads. Ilmenite has sometimes
been mistaken in the South African mines for carbonado. (F. W. R.*)
CARBONARI (an Italian word meaning "charcoal-burners"), the name of
certain secret societies of a revolutionary tendency which played an
active part in the history of Italy and France early in the 19th
century. Societies of a similar nature had existed in other countries
and epochs, but the stories of the derivation of the Carbonari from
mysterious brotherhoods of the middle ages are purely fantastic. The
Carbonari were probably an offshoot of the Freemasons, from whom they
differed in important particulars, and first began to assume importance
in southern Italy during the Napoleonic wars. In the reign (1808-1815)
of Joachim Murat a number of secret societies arose in various parts of
the country with the object of freeing it from foreign rule and
obtaining constitutional liberties; they were ready to support the
Neapolitan Bourbons or Murat, if either had fulfilled these aspirations.
Their watch-words were freedom and independence, but they were not
agreed as to any particular form of government to be afterwards
established. Murat's minister of police was a certain Malghella (a
Genoese), who favoured the Carbonari movement, and was indeed the
instigator of all that was Italian in the king's policy. Murat himself
had at first protected the sectarians, especially when he was
quarrelling with Napoleon, but later, Lord William Bentinck entered into
negotiations with them from Sicily, where he represented Great Britain,
through their leader Vincenzo Federici (known as Capobianco), holding
out promises of a constitution for Naples similar to that which had been
established in Sicily under British auspices in 1812. Some Carbonarist
disorders having broken out in Calabria, Murat sent General Manhes
against the rebels; the movement was ruthlessly quelled and Capobianco
hanged in September 1813 (see Greco, _Intorno al tentativo dei Carbonari
di Citeriore Calabria nel 1813_). But Malghella continued secretly to
protect the Carbonari and even to organize them, so that on the return
of the Bourbons in 1815 King Ferdinand IV. found his kingdom swarming
with them. The society comprised nobles, officers of the army, small
landlords, government officials, peasants and even priests. Its
organization was both curious and mysterious, and had a fantastic ritual
full of symbols taken from the Christian religion, as well as from the
trade of charcoal-burning, which was extensively practised in the
mountains of the Abruzzi and Calabria. A lodge was called a _vendita_
(sale), members saluted each other as _buoni cugini_ (good cousins), God
was the "Grand Master of the Universe," Christ the "Honorary Grand
Master," also known as "the Lamb," and every Carbonaro was pledged to
deliver the Lamb from the Wolf, i.e. tyranny. Its red, blue and black
flag was the standard of revolution in Italy until substituted by the
red, white and green in 1831.
When King Ferdinand felt himself securely re-established at Naples he
determined to exterminate the Carbonari, and to this end his minister of
police, the prince of Canosa, set up another secret society called the
_Calderai del Contrappeso_ (braziers of the counterpoise), recruited
from the brigands and the dregs of the people, who committed hideous
excesses against supposed Liberals, but failed to exterminate the
movement. On the contrary, Carbonarism flourished and spread to other
parts of Italy, and countless lodges sprang up, their adherents
comprising persons in all ranks of society, including, it is said, some
of royal blood, who had patriotic sentiments and desired to see Italy
free from foreigners. In Romagna the movement was taken up with
enthusiasm, but it also led to a certain number of murders owing to the
fiery character of the Romagnols, although its criminal record is on the
whole a very small one. Among the foreigners who joined it for love of
Italy was Lord Byron. The first rising actively promoted by the
Carbonari was the Neapolitan revolution of 1820. Several regiments were
composed entirely of persons affiliated to the society, and on the 1st
of July a military mutiny broke out at Monteforte, led by two officers
named Morelli and Silvati, to the cry of "God, the King and the
Constitution." The troops sent against them, under General Pepe, himself
a Carbonaro, sympathized with the mutineers, and the king, being
powerless to resist, granted the constitution (13th of July), which he
swore on the altar to observe. But the Carbonari were unable to carry on
the government, and after the separatist revolt of Sicily had broken out
the king went to the congress of Laibach, and obtained from the emperor
of Austria the loan of an army with which to restore the autocracy. He
returned to Naples early in 1821 with 50,000 Austrians, defeated the
constitutionalists under Pepe, dismissed parliament, and set to work to
persecute all who had been in any way connected with the movement.
A similar movement broke out in Piedmont in March 1821. Here as in
Naples the Carbonari comprised many men of rank, such as Santorre di
Santarosa, Count San Marzano, Giacinto di Collegno, and Count Moffa di
Lisio, all officers in the army, and they were more or less encouraged
by Charles Albert, the heir-presumptive to the throne. The rising was
crushed, and a number of the leaders were condemned to death or long
terms of imprisonment, but most of them escaped. At Milan there was only
the vaguest attempt at conspiracy; but Silvio Pellico, Maroncelli and
Count Confalonieri were implicated as having invited the Piedmontese to
invade Lombardy, and were condemned to pass many years in the dungeons
of the Spielberg.
The French revolution of 1830 had its echo in Italy, and Carbonarism
raised its head in Parma, Modena and Romagna the following year. In the
papal states a society called the Sanfedisti or Bande della Santa Fede
had been formed to checkmate the Carbonari, and their behaviour and
character resembled those of the Calderai of Naples. In 1831 Romagna and
the Marches rose in rebellion and shook off the papal yoke with
astonishing ease. At Parma the duchess, having rejected the demand for a
constitution, left the city and returned under Austrian protection. At
Modena, Duke Francis IV., the worst of all Italian tyrants, was expelled
by a Carbonarist rising, and a dictatorship was established under Biagio
Nardi on the 5th of February. Francis returned with an Austrian force
and hanged the conspirators, including Ciro Menotti. The Austrians
occupied Romagna and restored the province to the pope, but though many
arrests of Carbonari were made there were no executions. Among those
implicated in the Carbonarist movement was Louis Napoleon, who even in
after years, when he was ruling France as Napoleon III., never quite
forgot that he had once been a conspirator, a fact which influenced his
Italian policy. The Austrians retired from Romagna and the Marches in
July 1831, but Carbonarism and anarchy having broken out again, they
returned, while the French occupied Ancona. The Carbonari after these
events ceased to have much importance, their place being taken by the
more energetic Giovane Italia Society presided over by Mazzini.
In France, Carbonarism began to take root about 1820, and was more
thoroughly organized than in Italy. The example of the Spanish and
Italian revolutions incited the French Carbonari, and risings occurred
at Belfort, Thouars, La Rochelle and other towns in 1821, which though
easily quelled revealed the nature and organization of the movement. The
Carbonarist lodges proved active centres of discontent until 1830, when,
after contributing to the July revolution of that year, most of their
members adhered to Louis Philippe's government.
The Carbonarist movement undoubtedly played an important part in the
Italian Risorgimento, and if it did not actively contribute to the wars
and revolutions of 1848-49, 1859-60 and 1866, it prepared the way for
those events. One of its chief merits was that it brought Italians of
different classes and provinces together, and taught them to work in
harmony for the overthrow of tyranny and foreign rule.
BIBLIOGRAPHY.--Much information on the Carbonari will be found in R.M.
Johnston's _Napoleonic Empire in Southern Italy_ (2 vols., London,
1904), which contains a full bibliography; D. Spadoni's _Sette,
cospirazioni, e cospiratori_ (Turin, 1904) is an excellent monograph;
_Memoirs of the Secret Societies of Southern Italy_, said to be by one
Bertoldi or Bartholdy (London, 1821, Ital. transl. by A.M. Cavallotti,
Rome, 1904); Saint-Edme, _Constitution et organisation des Carbonari_,
P. Colletta, _Storia del Reame di Napoli_ (Florence, 1848); B. King,
_A History of Italian Unity_ (London, 1899), with bibliography.
(L. V.*)
CARBONATES. (1) The metallic carbonates are the salts of carbonic acid,
H2CO3. Many are found as minerals, the more important of such naturally
occurring carbonates being cerussite (lead carbonate, PbCO3), malachite
and azurite (both basic copper carbonates), calamine (zinc carbonate,
ZnCO3), witherite (barium carbonate, BaCO3), strontianite (strontium
carbonate, SrCO3), calcite (calcium carbonate, CaCO3), dolomite (calcium
magnesium carbonate, CaCO3.MgCO3), and sodium carbonate, Na2CO3. Most
metals form carbonates (aluminium and chromium are exceptions), the
alkali metals yielding both acid and normal carbonates of the types
MHCO3 and M2CO3 (M=one atom of a monovalent metal); whilst bismuth,
copper and magnesium appear only to form basic carbonates. The acid
carbonates of the alkali metals can be prepared by saturating an aqueous
solution of the alkaline hydroxide with carbon dioxide, M.OH + CO2 =
MHCO3, and from these acid salts the normal salts may be obtained by
gentle heating, carbon dioxide and water being produced at the same
time, 2MHCO3 = M2CO3 + HO2 + CO2. Most other carbonates are formed by
precipitation of salts of the metals by means of alkaline carbonates.
All carbonates, except those of the alkali metals and of thallium, are
insoluble in water; and the majority decompose when heated strongly,
carbon dioxide being liberated and a residue of an oxide of the metal
left. The alkaline carbonates undergo only a very slight decomposition,
even at a very bright red heat. The carbonates are decomposed by mineral
acids, with formation of the corresponding salt of the acid, and
liberation of carbon dioxide. Many carbonates which are insoluble in
water dissolve in water containing carbon dioxide. The individual
carbonates are described under the various metals.
(2) The organic carbonates are the esters of carbonic acid, H2CO3, and
of the unknown ortho-carbonic acid, C(OH)4. The acid esters of carbonic
acid of the type HO.CO.OR are not known in the free state, but J.B.
Dumas obtained barium methyl carbonate by the action of carbon dioxide
on baryta dissolved in methyl alcohol (_Ann._, 1840, 35, p. 283).
Potassium ethyl carbonate, KO.CO.OC2H5, is obtained in the form of
pearly scales when carbon dioxide is passed into an alcoholic solution
of potassium ethylate, CO2 + KOC2H5 = KO.CO.OC2H5. It is not very
stable, water decomposing it into alcohol and the alkaline carbonate.
The normal esters may be prepared by the action of silver carbonate on
the alkyl iodides, or by the action of alcohols on the chlorcarbonic
esters. These normal esters are colourless, pleasant-smelling liquids,
which are readily soluble in water. They show all the reactions of
esters, being readily hydrolysed by caustic alkalis, and reacting with
ammonia to produce carbamic esters and urea. By heating with
phosphorus pentachloride an alkyl group is eliminated and a
chlorcarbonic ester formed. Dimethylcarbonate, CO(OCH3)2, is a
colourless liquid, which boils at 90.6 deg. C., and is prepared by
heating the methyl ester of chlorcarbonic acid with lead oxide.
Diethylcarbonate, CO(OC2H5)2, is a colourless liquid, which boils at
125.8 deg. C.; its specific gravity is 0.978 (20 deg.) [H. Kopp]. When
it is heated to 120 deg. C. with sodium ethylate it decomposes into
ethyl ether and sodium ethyl carbonate (A. Geuther, _Zeit. f. Chemie_,
1868).
Ortho-carbonic ester, C(OC2H5)4 is formed by the action of sodium
ethylate on chlorpicrin (H. Bassett, _Ann._, 1864, 132, p. 54),
CCl3NO2 + 4C2H5ONa = C(OC2H5)4 + NaNO2 + 3NaCl. It is an
ethereal-smelling liquid, which boils at 158-159 deg. C., and has a
specific gravity of 0.925. When heated with ammonia it yields
guanidine, and on boiling with alcoholic potash it yields potassium
carbonate.
Chlorcarbonic ester, Cl.CO.OC2H5, is formed by the addition of
well-cooled absolute alcohol to phosgene (carbonyl chloride). It is a
pungent-smelling liquid, which fumes strongly on exposure to air. It
boils at 93.1 deg.C., and has a specific gravity of 1.144 (15 deg.
C.). When heated with ammonia it yields urethane. Sodium amalgam
converts it into formic acid; whilst with alcohol it yields the normal
carbonic ester. It is easily broken down by many substances (aluminium
chloride, zinc chloride, &c.) into ethyl chloride and carbon dioxide.
_Percarbonates._--Barium percarbonate, BaCO4, is obtained by passing
an excess of carbon dioxide into water containing barium peroxide in
suspension; it is fairly stable, and yields hydrogen peroxide when
treated with acids (E. Merck, _Abs. J.C.S._, 1907, ii. p. 859). Sodium
percarbonates of the formulae Na2CO4, Na2C2O6, Na2CO5, NaHCO4 (two
isomers) are obtained by the action of gaseous or solid carbon dioxide
on the peroxides Na2O2, Na2O3, NaHO2 (two isomers) in the presence of
water at a low temperature (R. Wolffenstein and E. Peltner, _Ber._,
1908, 41, pp. 275, 280). Potassium percarbonate, K2C2O6, is obtained
in the electrolysis of potassium carbonate at -10 to -15 deg.
CARBON BISULPHIDE, CS2, a chemical product first discovered in 1796 by
W.A. Lampadius, who obtained it by heating a mixture of charcoal and
pyrites. It may be more conveniently prepared by passing the vapour of
sulphur over red hot charcoal, the uncondensed gases so produced being
led into a tower containing plates over which a vegetable oil is allowed
to flow in order to absorb any carbon bisulphide vapour, and then into a
second tower containing lime, which absorbs any sulphuretted hydrogen.
The crude product is very impure and possesses an offensive smell; it
may be purified by forcing a fine spray of lime water through the liquid
until the escaping water is quite clear, the washed bisulphide being
then mixed with a little colourless oil and distilled at a low
temperature. For further methods of purification see J. Singer (_Journ.
of Soc. Chem. Ind._, 1889, p. 93), Th. Sidot (_Jahresb._, 1869, p. 243),
E. Allary (_Bull. de la Soc. Chim._, 1881, 35, p. 491), E. Obach (_Jour.
prak. Chem._, 1882 (2), 26, p. 282).
When perfectly pure, carbon bisulphide is a colourless, somewhat
pleasant smelling, highly refractive liquid, of specific gravity 1.2661
(18 deg./4 deg.) (J.W. Bruhl) or 1.29215 (0 deg./4 deg.) (T.E. Thorpe).
It boils at 46.04 deg. C. (T.E. Thorpe, _Journ. Chem. Soc._, 1880, 37,
p. 364). Its critical temperature is 277.7 deg. C., and its critical
pressure is 78.1 atmos. (J. Dewar, _Chem. News_, 1885, 51, p. 27). It
solidifies at about -116 deg.C., and liquefies again at about -110
deg.C. (K. Olszewski, _Jahresb._, 1883, p. 75). It is a mono-molecular
liquid (W. Ramsay and J. Shields, _Jour. Chem. Soc._, 1893, 63, p.
1089). It is very volatile, the vapour being heavy and very inflammable.
It burns with a pale blue flame to form carbon dioxide and sulphur
dioxide. It is almost insoluble in water, but mixes in all proportions
with absolute alcohol, ether, benzene and various oils. It is a good
solvent for sulphur, phosphorus, wax, iodine, &c. It dissociates when
heated to a sufficiently high temperature. A mixture of carbon
bisulphide vapour and nitric oxide burns with a very intense
blue-coloured flame, which is very rich in the violet or actinic rays.
When heated with water in a sealed tube to 150 deg. C. it yields carbon
dioxide and sulphuretted hydrogen. Zinc and hydrochloric acid reduce it
to tri-thioformaldehyde (CH2S)3 (A. Girard, _Comptes rendus_, 1856, 43,
p. 396). When passed through a red-hot tube with chlorine it yields
carbon tetrachloride and sulphur chloride (H. Kolbe). Potassium, when
heated, burns in the vapour of carbon bisulphide, forming potassium
sulphide and liberating carbon. In contact with chlorine monoxide it
forms carbonyl chloride and thionyl chloride (P. Schutzenberger, _Ber._,
1869, 2, p. 219). When passed with carbon dioxide through a red-hot tube
it yields carbon oxysulphide, COS (C. Winkler), and when passed over
sodamide it yields ammonium thiocyanate. A mixture of carbon bisulphide
vapour and sulphuretted hydrogen, when passed over heated copper, gives,
amongst other products, some methane.
Carbon bisulphide slowly oxidizes on exposure to air, but by the
action of potassium permanganate or chromic acid it is readily
oxidized to carbon dioxide and sulphuric acid. By the action of
aqueous alkalis, carbon bisulphide is converted into a mixture of an
alkaline carbonate and an alkaline thiocarbonate (J. Berzelius,
_Pogg. Ann._, 1825, 6, p. 444), 6KHO + 3CS2 = K2CO3 + 2K2CS3 + 3H2O;
on the other hand, an alcoholic solution of a caustic alkali converts
it into a xanthate (A. Vogel, _Jahresb._, 1853, p. 643),