Cooley's Cyclopaedia of Practical Receipts Volume I Part 126

Azuline. These will be found described under TAR COLOURS.

=CAR'BON.= C. _Syn._ CARBO'NIUM, CAR'BO, L.; CHARBON, Fr.; KOHLENSTOFF, Ger. An elementary or simple non-metallic solid body, very widely diffused through nature. Its purest and rarest form is that of the diamond. Nearly pure, it occurs very abundantly in the forms of graphite and anthracite.

In combination with oxygen, as carbonic acid, it exists in the atmosphere and in the waters of most springs, also in limestone, marble, chalk, and dolomite. Combined with hydrogen, it enters largely into coal, peat, and lignite. It is an essential const.i.tuent of organic matter, and hence it has been termed the "organic element." Charcoal, lamp-black, and c.o.ke, are more or less pure forms of carbon. By strongly igniting lamp-black in a covered crucible the element is obtained sufficiently pure for most chemical purposes.

It is best obtained purest by burning a jet of pure olefiant gas in an atmosphere of pure chloride, collecting the amorphous carbon deposited, and igniting in vacuo at a red heat.

Forms several chlorides, sulphides, &c., of which the following are the chief:--

=Carbon, Protochloride of.= Obtained from the sesquichloride by subliming it repeatedly through a tube filled with fragments of gla.s.s heated to redness. A transparent colourless liquid, with aromatic odour.

=Carbon, Sesquichloride of.= C_{2}Cl_{6}. Obtained by exposing Dutch liquid with chlorine, in a gla.s.s vessel, to the direct rays of the sun, taking care to renew the chlorine as long as it is absorbed. The liquid is ultimately converted into the sesquichloride of carbon, which is a white crystalline, volatile substance.

=Carbon, Tetrachloride of.= _Syn._ b.i.+.c.hLORIDE OF CARBON. It may be obtained by pa.s.sing chlorine (desiccated by being made to pa.s.s through a tube wetted with strong sulphuric acid), through a bottle containing bisulphide of carbon, and afterwards through a porcelain tube, wrapped in sheet copper, and filled with fragments of broken porcelain, maintained at a red heat, by a charcoal or gas furnace, and condensing the product in a bottle surrounded by ice. A mixture of tetrachloride of carbon and chloride of sulphur is thus obtained. By shaking this mixture with solution of potash, the chloride of sulphur is decomposed and dissolved, whilst the tetrachloride of carbon separates, and falls to the bottom. The upper layer having been poured off, the tetrachloride may be purified by distillation.

Tetrachloride of carbon is a colourless liquid, having a sp. gr. 16, and boiling at 172 F. It is insoluble in water, but dissolves in alcohol and ether. Its vapour, diluted with air, is employed as an anaesthetic.

=Carbon, Oxychloride of.= COCl_{2}. _Syn._ CHLO'ROCARBON'IC ACID, PHOSGENE GAS, CHLORIDE OF CARBONYL. Equal measures of carbonic oxide and chlorine are exposed to the direct rays of the sun; they combine, and become condensed to half their volume. It is a colourless, suffocating gas, which is immediately decomposed by water into carbonic and hydrochloric acids.

=Carbon, Sulphide of.= CS_{2}. _Syn._ BISULPHIDE OF CARBON, CARBON DISULPHIDE, SULPHURET OF CARBON. Bisulphide of iron (iron pyrites), 5 parts, and fresh dry charcoal, 1 part, are heated together in a stoneware retort, furnished with a gla.s.s tube, having the end bent, and pa.s.sing nearly to the bottom of a bottle or receiver filled with pounded ice. The bisulphide of carbon collects at the bottom of the receiver, and is then purified from adhering moisture and sulphur by distilling it, at a low temperature, from fused chloride of calcium.

By pa.s.sing the vapour of sulphur over fragments of charcoal, heated to bright redness in a porcelain tube, and collecting the product as before.

Sulphide of carbon is best manufactured by means of Peroncele's apparatus figured in the accompanying drawing.

[Ill.u.s.tration]

A is a fire-clay gas retort supported on the fire-clay block B; E and E are openings, one being that of a porcelain tube firmly cemented into the cover of A, serving for the introduction of sulphur; the other opening is for the introduction of pieces of c.o.ke, with which before the operation commences the retort is filled. The vapours of the sulphide of carbon pa.s.s through the tubes H and I into the vessel J, wherein part of the sulphide is condensed, and flows through K into the flask L, filled with water, thence through M into O, finally being run off by the tap N. Any vapours not condensed in J pa.s.s through P P into the worm T, the condensed sulphide being collected in S. The crude sulphide is rectified by redistillation over zinc or perchloride of mercury by means of a steam or water bath. If the perchloride is employed it should remain in contact with the crude sulphide for at least 24 hours before redistillation.

_Prop., Uses, &c._ A colourless, pungent, fetid liquid, having the sp. gr.

127. It is exceedingly volatile, boiling at 1185 Fahr., and has never been frozen. It is highly inflammable, burning with a pale-blue flame, and giving off sulphurous and carbonic-acid gases. It freely dissolves sulphur and phosphorus, and by spontaneous evaporation deposits the first in beautiful crystals. The solution of phosphorus is much used in electrotyping objects, which are coated with a conducting film by its means. Its refractive power is remarkably high, and on this account it is employed to fill hollow lenses for spectroscopes and other optical instruments. It produces intense cold by its evaporation. A spirit thermometer, having its bulb covered with cotton, if dipped into this fluid and suspended in the air, rapidly sinks from 60 to 0, and if put into the receiver of an air-pump it will fall to -81 Fahr. A mixture of sulphide of carbon and solid carbonic anhydride forms almost the most powerful frigorific agent known. Sulphide of carbon is now prepared on the large scale, and extensively employed as a solvent.

It is thus used for extracting from the cake of fruits and seeds the oil remaining in them after they have been submitted to pressure. The sulphide is subsequently separated from the oil by distillation. In Algiers it is used for obtaining the essential oils contained in the rose, jessamine, and lavender. It is also employed for dissolving the fat from bones, and from the crude wool. Furthermore, it is an excellent solvent for caoutchouc, as well as for the ordinary resins.

Its vapour is employed by agriculturists to kill the larvae infesting grain. Latterly, it has been employed as a disinfectant.

_a._ _Carbon Bisulphide as an Antiseptic._ By P. Zoller ('Deut. Chem. Ges.

Berl.,' ix, 1080-1084). The author has continued his experiments on this subject with the object of determining (1) the minimum quant.i.ty of bisulphide required, and (2) whether articles of food preserved by means of it are fit for human consumption.

As regards the first point, he found that meat of all kinds, and even entire animals, in quant.i.ties up to 20 kilograms, kept perfectly well for several weeks in vessels of sheet zinc, into which 5 grams of carbon bisulphide had been introduced, the meat being either simply hung on hooks or wrapped in cloths and laid on perforated shelves in the vessels.

Probably a smaller quant.i.ty of the bisulphide would suffice. Meat also kept well for 62 days in a vessel in which carbon bisulphide was liberated by introducing pota.s.sium xanthate and dilute sulphuric acid. Freshly baked bread, vegetables, and fruits of all kinds (asparagus, radishes, young beans, cuc.u.mbers, strawberries, raspberries, currants, cherries, peaches, apricots, lemons, &c.), and juices of fruits kept perfectly well in gla.s.s vessels, into which carbon bisulphide has been introduced, in the proportion of 5-10 drops for each litre of capacity.

Bread, vegetables, and fruit thus preserved are fit to eat after simple exposure to the air, and cannot be distinguished by taste or other qualities (except a slight loss of colour in some fruits) from fresh bread, &c. Meat retains even after exposure to air the disagreeable odour of carbon bisulphide. But besides this odour, which disappears on boiling or roasting, the meat has a slight smell of the volatile fatty acids and the taste of game. To most people, however, this taste is not unpleasant.

The presence of fatty acids is to be attributed to decomposition taking place in the interior of the meat, and not preventable by the carbon bisulphide, the function of which is merely to kill germs present in the air or on the surface of substances submitted to its influence.

_b._ By Hugo Schiff ('Deut. Chem. Ges. Ber.,' ix, 828). Coc.o.o.ns of silkworms which had been killed by exposure to the vapours of carbon disulphide underwent no change during six months' keeping in flasks in the laboratory. The bodies of some pigs which had been used for physiological experiments were put into a stoppered vessel with a few c. c. of carbon disulphide in 1869, and have been perfectly preserved without decomposition. The same result was obtained with a lizard 35-45 centimetres long, which had been suffocated accidentally in 1869, and was bottled whole. In this case a small quant.i.ty of liquid collected at the bottom of the vessel, and the green hue of the skin became a dirty greyish green, but not the slightest putrefaction occurred. Similar results were obtained with the intestines of poultry immersed in water in 1872 with a little carbon disulphide, in a bottle with a greased stopper; with a lump of beef weighing 200 grams; and with the body of a finch killed with paraconine. The beef yielded a normal flesh fluid, and was eaten by a dog without hesitation even after several months.

_Purification._--1. It is stated that the odour of sulphide of carbon can be readily removed by allowing it to stand over mercury or corrosive sublimate for some time, and then redistilling.

2. The following method by Kern is stated by him to be the best for purifying sulphide of carbon:--The impure product is well mixed in a tall gla.s.s vessel with some lead nitrate, and with a small quant.i.ty of metallic lead. When the salt turns dark the liquid is poured into another vessel with a fresh quant.i.ty of the lead salt; and so on until the salt remains nearly white while mixed with the liquor. The sulphide of carbon is then placed in a retort, and distilled over into a well-cooled receiver.

3. M. Yvon proposes a process which consists in adding copper turnings to the sulphide; no slaking is necessary. The sulphide soon becomes nearly colourless, and loses its usually unpleasant odour. Miller says reduced copper produces the same result.

Carbon sulphide is employed therapeutically in doses of 2 drops, gradually increased to 5, as a sudorific in rheumatism. It is also dropped (40 to 50 drops) on the part, to promote the reduction of strangulated hernia.

Externally, it is employed in liniments for rheumatic pains.

=CAR'BONATE=, a salt in which the hydrogen of (hypothetical) carbonic acid (H_{2}CO_{3}) is replaced by a metal or other basic radical.

_Prep., &c._ The processes by which the commercial carbonates and many others are prepared are described under the respective bases. Most of the earthy carbonates are found abundantly in nature. In general the salts of this cla.s.s may be formed by adding an alkaline carbonate to a salt of the metal in solution by double decomposition.

_Prop._ The carbonates of the alkalies are soluble in water; those of the other bases are for the most part insoluble, except the water is highly charged with carbonic acid. From most of them carbonic anhydride or anhydrous carbonic acid can be easily expelled by heat.

_Tests._ The carbonates are easily distinguished by the following reactions:--They dissolve with effervescence in hydrochloric acid and in most other acids; in some cases a gentle heat is required to promote the disengagement of the gas.--The gas evolved in the last, pa.s.sed into lime water and baryta water, occasions white precipitates, which redissolve in acids with effervescence, and after the solution has been boiled are not reprecipitated by liquor of ammonia.--Chloride of calcium and chloride of barium give white precipitates in solutions of the neutral alkaline carbonates, but in solutions of the alkaline bicarbonates only after ebullition; and the precipitates are readily soluble with effervescence in acetic acid.

_Estim._ The quant.i.ty of the metal in an alkaline or earthy carbonate may be easily determined by the ordinary volumetric methods of alkalimetry (which _see_), and the quant.i.ty of carbonic acid, by the method of Fresenius and Will (see ALKALIMETRY). The apparatus figured on next page, or preferably that shown in the article on ALKALIMETRY, may be used instead of the more complicated contrivance of the German chemists.

A weighed sample of the carbonate to be examined is placed in the flask _a_ along with a little water, and the small tube, _b_, filled with either sulphuric or hydrochloric acid, is carefully introduced. The cork, with its chloride of calcium tube, _d_, is then fitted to the flask, and the whole apparatus very accurately weighed.

On inclining the apparatus the acid escapes over the side of the small tube, and mixing with the liquor in the flask, expels the carbonic acid of the carbonate, which is then dried by pa.s.sing over the chloride of calcium. After effervescence has ceased heat should be applied to the bottom of the flask, until it be filled with steam, to expel the carbonic gas it contains. The loss of weight gives the weight of the carbonic acid gas that was contained in the sample. The quant.i.ty of carbonic acid in the carbonates of the metals that do not contain water may be determined by heating them to redness in a platina crucible.

[Ill.u.s.tration: _a_, Flask containing the sample of carbonate for examination, stopped by a closely fitting cork, through which pa.s.ses the bent tube _c_.

_b_, A small tube, sufficiently long to maintain a slanting position without falling, filled with sulphuric or hydrochloric acid.

_c_, A bent tube, connecting the flask with _d_.

_d_, Horizontal tube, filled with small fragments of fused or dried chloride of calcium, with a fine orifice at the extremity _e_.]

=CARBONIC ACID.= H_{2}CO_{3}. True carbonic acid has not yet been obtained in any satisfactory condition, although the solution of carbonic anhydride (often called carbonic acid), or anhydrous carbonic acid, is generally regarded as such. It forms with bases an important series of salts, called the carbonates, by double decomposition.

=CARBONIC ANHYDRIDE.= CO_{2}. _Syn._ CARBONIC ACID, CARBON DIOXIDE, FIXED AIR, CHOKE DAMP; ACIDE CARBONIQUE, Fr.; KOHLEN SaURE, Ger. A compound formed by the chemical union of carbon and oxygen.

_Hist._ Van Helmont recognised carbonic acid as a peculiar gas. Dr Black, in 1757, proved that it was a const.i.tuent of limestone, and gave it the name of fixed air; he also showed that the causticity of alkalies depended on its absence. Bergmann first described it as an acid, applying to it the term aerial acid. Lavoisier, in 1776, established its true nature, and gave it the name it now bears. Faraday, in 1823, by pressure at an extremely low temperature, reduced carbonic acid to a liquid, and a few years later Thiloria and Brunel obtained it in the solid form.

_Nat. Hist._ Carbonic acid is a const.i.tuent of the atmosphere, its presence being essential to the existence of vegetable life on the globe.

It issues from the earth in many situations, as the Grotto del Cane in Italy, the Valley of Poison in Java, and near the Lake of Laach in Germany. It gives to many mineral springs their sparkling brilliancy, and is held in solution by all natural waters. Combined with the bases, lime and magnesia especially, it exists in large quant.i.ties in the crust of the earth. It is the chief product of combustion, and one of the products of fermentation. It is always being exhaled by animals in the process of respiration, and in smaller quant.i.ties by plants at night or in the shade.

It forms the terrible "choke-damp" or "after-damp" of the coal mines. It is the gas disengaged during the effervescence of soda water and other aerated drinks, and the cause of the freshness of newly-drawn beer.

_Prep._ Hydrochloric acid, 1 part, diluted with water, 4 or 5 parts, is poured upon fragments of white marble, previously placed in a suitable generating apparatus.[237]

[Footnote 237: A large flask, provided with a bent gla.s.s tube for conveying the gas, and a tube-funnel for introducing the acid, is the most convenient form of apparatus. A tubulated retort may be used, but the generating flask or bottle is to be preferred.]

Carbonic acid is rapidly evolved, and may be collected, with some loss, over water in the pneumatic trough. If required dry, the gas must be pa.s.sed over fragments of fused chloride of calcium, placed in a large tube, or through a small quant.i.ty of concentrated sulphuric acid, and collected by displacement or over mercury.

From oil of vitriol, 1 part; water, 6 parts; and chalk or whiting, 1-1/4 part; mixed in a suitable vessel, applying agitation.

_Prop._ Under ordinary conditions carbonic acid is a colourless, non-inflammable, irrespirable gas, possessing a slightly pungent odour, and an acidulous taste. Water absorbs its own volume of this gas, and by pressure may be made to take up enormous quant.i.ties, forming carbonated or aerated water. Its sp. gr. is 1520; hence it may be poured from one vessel to another like water. By a pressure of thirty atmospheres at 32 Fahr. it is liquefied, the pressure required decreasing as the temperature gets lower. At -94 Fahr. it solidifies into a vitreous transparent ma.s.s.

Carbonic acid, even when greatly diluted with air, cannot be inhaled without insensibility following. An atmosphere containing more than its natural quant.i.ty of gas (1 part in 2500 parts by measure) acts upon the system as a narcotic poison; hence the danger of over-crowded rooms. It is a non-supporter of combustion, at once extinguis.h.i.+ng a lighted candle, gas-jet, or even a piece of burning phosphorus, when these are placed in a jar of the gas.