Chapter II: BLEACHING of =Linen=:--Linen may be bleached in a similar way to (17)

9. (Kuhlman.) This chemist proposes saturating the hot lemon juice as far as possible with very finely divided barium carbonate, and afterwards completing the neutralisation with barium hydrate or sulphide. The precipitated barium citrate is then to be washed, and decomposed with the requisite quantity of sulphuric acid. The advantage of barium over lime as a precipitant is the more ready crystallisability of the citric acid from the solution thus obtained. Sulphate of baryta is absolutely insoluble in solution of citric acid, whilst sulphate of lime is not; and the presence of the latter impedes the crystallisation of the acid.

_Obs._ If the lemon or lime juice be allowed to ferment a short time, the mucilage and other impurities will, to a certain extent, separate and subside. See _Concluding Remarks_.

_Prop., Uses, &c._ Citric acid forms rhomboidal prisms, which are clear, colourless, odourless, sour, and deliquescent in a moist atmosphere. It is an agreeable acid, at once cooling and antiseptic. It is much used in medicine as a substitute for lemon juice, and to form effervescing draughts, citrates, &c.

17 gr. citric acid, in crystals, or 1/2 fl. oz. of
lemon juice,

\---------------------v--------------------------/
are equivalent to
/----------^---------------\
25 gr. bicarbonate of potash;
20 " carbonate of potash;
15 " carbonate of ammonia;
20 " bicarbonate of soda;
35 " carbonate of soda.

The bicarbonate of potassa is that generally preferred for making saline draughts with citric acid; and when flavoured with a little tincture of orange peel and simple syrup, or syrup of orange peel alone, it forms a most delicious effervescing beverage. Citric acid in pure crystals or in lime juice is much used by the calico-printer, being the best known 'resistant' for iron and alumina mordants.

_Pur._ Citric acid is frequently met with adulterated with tartaric acid; the fraud is easily detected by dissolving the acid in a little cold water, and adding to the solution a small quantity of acetate of potash. If tartaric acid be present, a white, crystalline precipitate of cream of tartar will be produced on agitation. When pure it is devoid of colour, is entirely, or almost entirely, decomposed by heat. It is soluble in water and in spirit, and what is thrown down from its watery solution by acetate of lead is dissolved by nitric acid. No salt of potassium precipitates anything with citric acid except the tartrate. When a few drops of a solution of citric acid are added to lime water, a clear liquid results, which, when heated, deposits a white powder, soluble in acids without effervescence. By the action of nitric acid citric acid is converted into oxalic acid.

When the crystals of citric acid are very deliquescent, the presence of free sulphuric acid may be suspected. This latter may be detected with facility by dissolving the citric acid in a little water, strongly acidifying the solution with hydrochloric acid, and adding chloride of barium, when, if sulphuric acid be present, an insoluble precipitate of sulphate of barium will fall down after a short time. Oxalic acid is sometimes present in citric acid, the cause of its presence being explained further on. To test for it proceed as follows:

Dissolve a small quantity of the citric acid in water, and add to the solution an excess of ammonia; acidify with acetic acid, filter, and test the filtrate with calcium sulphate.

_Estim._ See ACIDIMETRY and LIME JUICE.

_Tests._ See _above_.

_Concluding Remarks._ The preparation of citric acid has now become an important branch of chemical manufacture, from the large consumption of this article in various operations in the arts. In conducting the different steps of the process some little expertness and care are, however, necessary to ensure success. The chalk employed, which should be dry, and in fine powder, is added to the juice from a weighed sample, until the latter is perfectly neutralised, and the quantity consumed is exactly noted. The precipitated citrate of lime is next thoroughly washed with water, and the sulphuric acid, diluted with 6 or 8 times its weight of water, whilst still warm, is poured upon it, and thoroughly mixed with it. The agitation is occasionally renewed for 8 or 10 hours or longer, when the solution of citric acid is poured off, and the residuum of sulphate of lime thoroughly washed with warm water, the washings being added to the liquid acid. This last is then poured off from the impurities that may have been deposited, and evaporated in a leaden boiler, over the naked fire, or by high-pressure steam, until it acquires the gravity of 1·13, when the process is continued, at a lower temperature, until a syrupy aspect is assumed, and a pellicle appears on the surface of the liquor. Without great care at this part of the process the whole batch may be carbonised and spoiled. At this point the concentrated solution is emptied into warm and clean crystallising vessels, set in a dry apartment, where the thermometer does not fall below temperate. At the end of 4 days the crystals are found ready for removal from the pans. They are thoroughly drained, redissolved in as little water as possible, and after being allowed to stand for a few hours to deposit impurities, again evaporated and crystallised.

The acid of the second crystallisation is usually sufficiently pure for the market; when this is not the case a third, or even a fourth, crystallisation must be had recourse to. The mother-liquors from the several pans are now collected together, and a second or third crop of crystals obtained from them, by evaporation as before.

A frequent cause of difficulty in obtaining crystals from the solutions is the employment of too little sulphuric acid to decompose the whole of the citrate of lime; the consequence of which is that a little of that salt is taken up by the free citric acid, and materially obstructs the crystallisation. Forty parts of dry sulphuric acid are required to decompose 50 parts of chalk. Commercial sulphuric acid (oil of vitriol) is usually of the sp. gr. of 1·845, and it therefore requires 49 lbs. of this acid for every 50 lbs. of chalk employed in the process. In practice it is found that a very slight excess of sulphuric acid is preferable to a preponderance of undecomposed citrate of lime.

The first crop of crystals is called 'brown citric acid,' and is chiefly sold to the calico-printers. Sometimes a little nitric acid is added to the solution of the coloured crystals, for the purpose of bleaching them, but in this way a minute quantity of oxalic acid is formed. A more general plan is to bleach the citrate of lime by covering it with a weak solution of chloride of lime, exposing it in shallow vessels to the sun's rays, and rewashing it before decomposing it with sulphuric acid. A safer plan is to dissolve the crude citric acid, digest with animal charcoal, and again concentrate the solution to the crystallising point.

When the aqueous solution of citric acid obtained, as already described, is concentrated by boiling in an open evaporating pan, the acid is not only liable to suffer partial decomposition by its long exposure to the air, but it not unfrequently acquires a brown colour from the carbonisation those portions of the liquid undergo which are in contact with the bottom of the pan, which being heated by high-pressure steam frequently reaches a temperature exceeding 200° F. This latter result is brought about in consequence of the slight movement in the dense acid liquor in the pan. To remedy the loss and inconvenience arising from the employment of the open evaporating pan, some years back Mr Pontifex devised an apparatus which effects the evaporation of acid liquor _in vacuo_ (and therefore out of contact with air), and at a temperature never exceeding 130 F°. Moreover, in Mr Pontifex's boiler the time necessary for the concentration of the citric-acid liquor is diminished to about an eighth, and as the strong ebullition keeps the liquid in constant motion its charring is entirely prevented.

Mr Row says that lemon juice may be purified to a great extent by diluting it with water until it contains about 12 oz. of acid to the gallon, and then filtering from the flocculent precipitate of mucilage thus thrown down. The citrate of lime obtained from juice so treated is comparatively pure.

Good lemon juice yields about 6-1/2% of crystallised lemon acid; 2 galls. yield fully 1 lb. of crystals. See LEMON JUICE, LIME JUICE. &c.

=CIT'RON.= The fruit of the citron tree (_Citrus medica_) is acidulous, antiseptic, and antiscorbutic; it excites the appetite, and stops vomiting; and, like lemon juice, has been greatly extolled in chronic rheumatism, gout, and scurvy. Mixed with cordials, it is used as an antidote to the manchineel poison.

=Citron, Oil of.= See OIL.

=Citron Peel.= This is prepared in the same way as candied orange and lemon peel, which it for the most part resembles.

=Citron.= _Syn._ LEM'ON COLOUR. The term applied to a pale and delicate shade of yellow. See YELLOW DYES, &c.

=CIT'RONELLE.= See LIQUEURS and OILS (Lemon-grass).

=CITRUS.= A genus of plants belonging to the natural order _Aurantiaceæ_, the species of which yields useful fruits. From _Citrus Aurantium_, and its varieties, all the various descriptions of sweet oranges are obtained. The species _C. Bigaradia_ or _vulgaris_ yields the bitter or Seville orange; _C. Limonum_ and its varieties, yield the lemons; _C. Limetta_ is the source of the lime; _C. medica_ of the citron; _C. Decumana_ of the shaddock; _C. paradisi_ of the forbidden fruit; _C. Pampelmos_ of the Pampelmoose; and _C. japonica_ of the kumquat.

=Citrus Bergamia.= (Ind. Ph.) _Syn._ THE LIME TREE. _Habitat._ Commonly cultivated in India and other tropical countries.--_Officinal part._ The fruit (lime) closely resembles the lemon, but is smaller, with a smoother, thinner rind, and of somewhat less fragrant odour. Its juice (lime juice) has the same pungent acid taste, and contains the same ingredients as lemon juice, though in somewhat different proportions, that of the citric acid being larger and that of the mucilage less in quantity. Much of the article imported into England under the name of lemon juice is obtained from the lime.--_Properties and Uses._ Very similar to those of the lemon, the juice being equally refrigerant and antiscorbutic; indeed, it is preferred by many tropical practitioners.

The fresh juice of the lime is procurable in almost every portion of the tropics, and is considered more effectual than preserved lemon juice.

Lime juice may be advantageously employed in the manufacture of citric acid, the proportion of this acid being larger than in lemon juice.

=CIV'ET.= _Syn._ CIVET'TA ZYBETH'UM, L. A perfume obtained from the civet cat (_Viverra civella_, Linn.), a fierce, carnivorous quadruped, somewhat resembling a fox, found in China and the East and West Indies. The civet is secreted in a sort of pouch between the anus and the sexual organs. "Several of these animals have been brought into Holland, and afford a considerable branch of commerce, especially at Amsterdam. The civet is squeezed out in summer every other day, in winter twice a week; the quantity procured at once is from 2 scruples to 1 drachm or more."

Civet is frequently adulterated with spermaceti and butter, and a similar substance to civet, but of a darker colour, obtained from the polecat. When pure it has an odour intermediate between that of musk and ambergris, but less refined; a pale-yellow colour; an acrid taste; and the consistence of honey. It is used in perfumery.

=CLAIRET.= See LIQUEUR.

=CLAR'ET RAGS.= _Syn._ TOURNESOL EN DRAPEAU, Fr.; BEZET'TA C[OE]RU'LEA, L. 1. Pieces of clean linen coloured with Auvergne--or ground archil.

2. Pieces of linen dipped into the juice of mulberries, blood-red grapes, lees of red wine, &c. Used to colour jellies, confectionery, the rind of cheeses, &c.

=CLARIFICATION.= The act of clearing or making bright; commonly applied to the process of 'clearing' or 'fining' the liquids by chemical means, instead of by filtration. The substances used for this purpose are popularly known as 'clarifiers' or 'finings.'

The substances employed in the clarification of liquids operate by either mechanically embracing the feculous matter, and subsiding with it to the bottom of the vessel, or by inducing such a change in its nature or bulk that it subsides by its own density, in each case leaving the liquor transparent. Albumen, gelatin, the acids, certain salts, blood, lime, plaster of Paris, alum, heat, alcohol, &c., serve in many cases for this purpose. The first is used, under the form of white of egg, for the clarification of syrups, as it combines with the liquid when cold, but on the application of heat rapidly coagulates and rises to the surface, carrying the impurities with it, forming a scum which is easily removed with a skimmer. It is also much used for fining wines and liqueurs, particularly the red wines and more limpid cordials. Gelatin, under the form of isinglass, dissolved in water or weak vinegar, is used to fine white wines, beer, cider, and similar liquors that contain a sufficient quantity of either spirit or astringency (tannin), to induce its precipitation. Sulphuric acid is frequently added to weak liquors for a similar purpose, either alone or after the addition of white of egg or gelatin, both of which it rapidly throws down in an insoluble form. A pernicious practice exists among some unprincipled manufacturers of using certain salts of lead and potash to clear their liquors; especially those that are expected to sparkle in the glass, as 'cordial gin,' &c. For this purpose a little sugar of lead, dissolved in water, is first mixed up with the fluid, and afterwards a little more than half its weight of sulphate of potassa, also dissolved in water, is added, and the liquor is again 'roused' up. By standing, the sulphate of lead, formed by this mixture, subsides, and leaves the liquor clear. Bullock's blood is used in the same way as isinglass or white of eggs, for fining red wines, beer, and porter. Lime, alum, alcohol, acids, and heat, act by curdling or coagulating the feculencies, and thus, by increasing their density, induce their subsidence. Plaster of Paris acts, partly like the above, and partly like albumen, or gelatin, by developing and forcing down the suspended matter. Sand is often sifted over liquors (especially cordials and syrups), for the simple purpose of acting by its gravity, but appears to be quite useless, as it sinks too rapidly. The juices of plants are clarified by heat, which coagulates the albumen they contain. Marl or clay is frequently used to clear cider and perry. A strip of isinglass is generally employed to clarify coffee. See WINE, BREWING, CORDIALS, COFFEE, FININGS, INFUSION, &c.

=CLAY.= Clay is formed from the disintegration of felspathic rocks, by the combined action of air and water. Its plasticity, when moist, and its capability of being made hard by heat, are properties which render it available for many useful purposes. The purest kind of clay is kaolin, or China clay, which consists almost entirely of silicate of aluminum. It is found in China; but a precisely similar substance is obtained from deposits in Cornwall and some parts of France. Pipe-clay, a white clay nearly free from iron, is found in large quantity in the island of Purbeck. Potter's clay is found in many parts of Britain; that of Devonshire and Dorsetshire is much valued. Brick clay contains varying proportions of iron; hence the different colours of the bricks used in different countries. See ALUMINUM, FULLER'S EARTH, OCHRE, &c.

=CLEAN'ING.= In domestic economy the best way to clean a house is to keep it clean by a daily attention to small things, and not allow it to get into such a state of dirtiness and disorder as to require great and periodical cleanings. Some mistresses, and also some servants, seem to have an idea that a house should undergo regular cleanings, or great washing and scrubbing matches, once every three or six months, on which occasions the house is turned almost inside out, and made most uncomfortable. All this is bad economy, and indicates general slovenliness of habits. (Chambers.) For hints upon cleaning, see CARPETS, CLOTHES, &c.

=CLEAN'LINESS.= See ABLUTION, BATHING, and SICKNESS.

=CLIPPING= (HORSES). Some horses should be worked in autumn in cloths, or with their coats on, as, on account of the extra sweating thus caused, they will be in better condition for the hunting season. Such horses should be clipped or shaved. The horse's coat should be fully set before it is clipped. Those horses which sweat much in autumn should be singed. Singeing cannot be begun too early. The fresh growth must be removed every week. Singeing may be best accomplished by means of gas.

=CLOTHES.= Economy and cleanliness require due attention to be paid to every article of clothing, but more especially to those which are the most exposed to dirt and the weather. The following remarks, having reference chiefly to woollen articles, may prove useful to the reader:--If very dusty, hang them on a horse or line, and gently beat them with a cane; then lay them on a clean board or table and well brush them, first with a stiff brush, to remove the spots of mud and the coarsest of the dirt, and next with a softer one, to remove the dust and to lay the nap properly. If clothes are wet and spotted with dirt, dry them before brushing them, and then rub out spots with the hands. The hard brush should be used as little as possible, and then with a light hand, as it will, if roughly and constantly employed, soon render the cloth threadbare. Spots of tallow-grease on the clothes may be taken off with the nail, or, if that cannot be done, have a hot iron with some thick brown paper, lay the paper on the part where the grease is, then put the iron upon the spot; if the grease comes through the paper put on another piece, till it ceases to soil it. Moths may be prevented attacking clothes by putting a few cloves or allspice into the box or closet with them. See BALLS, CLOTHES, and SCOURING, &c.

=CLO''THING.= In our changeable climate great care should be taken to clothe the body effectually; for when the skin is chilled the blood is determined in increased and injurious quantity to the internal organs, causing colds and inflammations. The ordinary materials for clothing are cotton, linen, woollen, and silk. Cotton is generally employed for undergarments, for which its softness and warmth render it well adapted. Linen is not nearly so warm, but it keeps its colour better; it is more expensive, and although it wears much longer, it is not so economical as cotton. Woollen garments are, in cold and variable climates, almost essential to comfort; the warmth obtained by wearing flannel next the body is very beneficial, and the slight stimulating effect arising from its roughness tends to keep the skin in healthy action.

The practice of dressing infants in long clothes is a very objectionable one, for besides being injurious to health it cramps the action of the legs, the feet, and the toes, and by so doing prevents their proper and healthy development.

An infant should be so clothed as to combine sufficient warmth with perfect freedom of the limbs; hence his garments should be loose instead of tight, more particularly round his waist.

In the selection of winter clothes for children, if for in-door wear, choice should be made of a dark woollen frock, and of stockings in preference to socks. The stockings should be of merino, and made to draw above the knees and fastened to the dress with a loop and tape instead of garters, which are very objectionable.

A child's out-of-door attire in winter should additionally comprise a warm and properly-lined coat, made of cloth or some woollen fabric. It should button close to the chin and cover his neck. Mr Chavasse says, for this latter purpose a woollen neckerchief or scarf is preferable to furs. It is very important that the child's feet and legs should be kept warm, but not too warm. In infancy and childhood--in summer as well as winter--the wearing of flannel next the skin is more necessary, and beneficial even, than when practised by adults.

=CLOVE.= _Syn._ CARYOPH'YLLUM (B. P.), L. The flower-buds of the _Ciryophyllus aromaticus_ (Linn.), or clove tree collected before they open, dried, and smoked. Cloves are aromatic, stimulant, carminative, and stomachic; and, according to some, possess febrifuge properties. They are chiefly used as an adjuvant in compound medicines. A few cloves kept in a closet or box prevent moths or mould attacking furs, woollens, &c.

It is a common practice to adulterate this spice in the same manner as cinchona bark. Cloves from which the oil has been distilled are dried and rubbed between the hands, previously moistened with a little sweet oil, to brighten their colour, after which they are mixed up with fresh spice for sale.

=Cloves, Mother of.= The unripe fruit of the clove tree; they are frequently imported preserved (preserved mother of cloves), and are reputed stomachic and antispasmodic.

=Cloves, Oil of.= _Syn._ O'LEUM CARYOPH'YLLI (B. P.), L. This possesses similar virtues to the unexpanded flower-buds, and is esteemed as a remedy for the tooth-ache. Used to flavour liqueurs and confectionery. Sp. gr. 1·055-1·060.

M. Jacquemin recommends the following as a very delicate test for the presence of carbolic acid when used as an adulterant for oil of cloves. One drop of the suspected oil is mixed with a small trace of solution of aniline by means of a glass rod, and then shaken with 5 or 6 c. c. of distilled water. By the addition of a few drops of sodium hypochlorite to the mixture the characteristic blue coloration due to carbolic acid will be developed in a few minutes, whereas with the pure oil nothing but the purplish-violet colour of aniline will be perceived. Stirring or shaking must be avoided after the addition of the hypochlorite.

=CLYS'TERS.= See ENEMA.

=COAL.= The varieties of this valuable substance may be conveniently described under the three heads ANTHRACITE, LIGNITE, and PIT-COAL (which _see_). See also FUEL.

=COAL-TAR.= Coal-tar, one of the products of the destructive distillation of the coal employed in the manufacture of gas, is a very complex substance, consisting of various hydrocarbons, acids, and bases, together with certain resinoid and empyreumatic substances. The principal hydrocarbons yielded by coal-tar on distillation are: benzol, toluol, propyl, naphthalin, and anthracin; of these the first three are fluids, and the last two solids; the most important acids are: carbolic, cresylic, phlorylic, and nosolic; the chief bases are: aniline, chinoline, and lepidine. The quantity as well as the quality of the tar obtained from the distillation of coals varies considerably with the kind of coal used, as well as with the temperature at which the distillation is carried on, the yield of tar being smaller at very high temperatures than when lower ones are employed. Coal-tar, from its antiseptic properties (due chiefly to the carbolic acid it contains), is painted on wood to preserve the latter from decay when exposed to wind and weather. Mixed with coal-dust, saw-dust, and peat-dust, it forms a useful artificial fuel, and when incorporated with pebbles makes an excellent artificial asphalt for pavements. The chief value of coal-tar, however, consists in its being the source of those brilliant dye-stuffs, the coal-tar colours. These, together with the naphtha obtained from its distillation, have converted coal-tar from a worthless and unwelcome waste product of gas manufacture--for the removal of which from their premises the gas makers were formerly only too glad to pay--into a very considerable and important branch of profit and revenue.

The different constituents of the tar are separated from each other by distillation, the various products so obtained being further purified by various processes.

See TAR COLOURS, NAPHTHA, BENZOL, ANTHRACENE, &c.

=CO'BALT.= Co. _Syn._ REG'ULUS OF COBALT; COBALT'TUM, L. A metal discovered by Brandt, in 1733. It generally occurs in the same ore as nickel, and the separation of the two metals is a task requiring great patience and expertness. Speiss cobalt and cobalt glance are the ores from which the metal is commonly extracted.

_Prep._ 1. Dissolve oxide of cobalt in hydrochloric acid, and pass sulphuretted hydrogen gas through the solution, until all the arsenic is thrown down; filter, and boil with a little nitric acid, then add carbonate of potassium, in excess, and digest the precipitate in a solution of oxalic acid, to remove any oxide of iron; wash and dry the residuum (oxalate of cobalt), and expose it to great heat, in a covered crucible lined with charcoal; the product is pure metallic cobalt.

2. Mix equal parts of oxide of cobalt or roasted Cornish cobalt ore, and soft soap, and expose them to a violent heat in a covered crucible.

3. Pass hydrogen gas over oxide of cobalt strongly heated in a porcelain tube.

_Prop., Use, &c._ Cobalt is a white, brittle metal; unchanged in the air; feebly acted on by dilute hydrochloric and sulphuric acids; has a high melting-point, and is strongly magnetic; sp. gr. 8·5. It is seldom employed in the metallic state, from the great difficulty of reducing its ores, but its oxide (black oxide) is largely employed in the arts. It forms salts with the acids, which are interesting from the remarkable changes of colour which they exhibit. See INK, SMALTS, ZAFFRE, and _below_.

_Char., Tests._ Solutions of the salts of cobalt are known as follows:--1. Ammonia gives a blue precipitate, slightly soluble in excess, giving a brownish-red colour.--2. Potassa gives a blue precipitate, turning to violet and red when the solution is heated.--3. Carbonate of ammonium and carbonate of sodium give pink precipitates; that from the former is soluble in excess.--4. Cyanide of potassium gives a yellowish-brown precipitate, soluble in excess; and the clear solution, after being boiled, is unaffected when mixed with hydrochloric acid.--5. Sulphuretted hydrogen produces no change in acid solutions.--6. Sulphydrate of ammonium gives a black precipitate in neutral solutions.--7. Melted with borax, before the blowpipe, it gives a bead of a magnificent blue colour, almost verging on black, if much is present. Phosphate of sodium and ammonium give a similar bead; but the colour is less intense.

=Cobalt, Ac'etate of.= Co(C_{2}H_{3}O_{2})_{2}. _Prep._ From the carbonate or protoxide and acetic acid. It forms a sympathetic ink which turns blue when heated.

=Cobalt, Arseniate of.= Co_{3}2AsO_{4}, 8H_{2}O. A hydrated native tricobaltous arseniate of cobalt, known as "cobalt bloom."

=Cobalt, Car'bonate of.= CoCO_{3}. _Prep._ By adding an alkaline carbonate to a solution of the nitrate or sulphate. A pale peach-coloured powder, soluble in acids. It contains some hydrate.

=Cobalt, Chlo''ride of.= CoCl_{2}. _Syn._ HYDROCHLO''RATE OF C., MU''RIATE OF C. _Prep._ By dissolving the carbonate or protoxide in hydrochloric acid; the solution deposits deep rose-red crystals on standing, which contain water. By evaporating the solution by heat, anhydrous blue crystals of the chloride are obtained. Both of them yield a deep rose-red solution with water, which is turned green by a little acid. This solution forms a well-known sympathetic ink, the traces of which become blue when heated. If the solution contains either chloride of iron or chloride of nickel, the traces become green. (Klaproth.) The addition of a little nitrate of copper to the above solution forms a sympathetic ink, which by heat gives a very rich greenish-yellow colour. (Ure.) The addition of a very little common salt makes the traces disappear with greater rapidity, on the withdrawal of the heat. In each case, when the paper is laid aside, moisture is absorbed, and the writing once more disappears. If, however, much heat has been used the traces become permanent.

=Cobalt, Ni'trate of.= Co(NO_{3})_{2}. _Prep._ As the last, substituting nitric for hydrochloric acid; it forms deliquescent crystals.

=Cobalt, Ox'alate of.= CoC_{2}O_{4}. _Prep._ As the acetate, from oxalic acid and the carbonate or protoxide; or by double decomposition.

=Cobalt, Ox'ides of.= Of these there are two, the protoxide and the sesquioxide; besides an acid compound of cobalt and oxygen, to which the name cobaltic acid has been given.

1. =Cobalt, Protox'ide of.= CoO. _Syn._ OXIDE OF COBALT, GREY O. OF C., BLACK O. OF C., COBALT BLACK. _Prep._ 1. By precipitating a solution of sulphate of chloride of cobalt with carbonate of sodium, and washing, drying, and igniting the powder which subsides.

2. By boiling powdered bright-white cobalt ore (from Cornwall) in dilute nitric acid, and adding a solution of carbonate of potassium, very gradually, until the clear liquor, after the impurities have settled, becomes of a rose colour; and then as long as a precipitate falls; wash and dry it as before.

_Prop., &c._ A grey powder, turning black on exposure to the air; strongly basic; and forming salts with the acids, having a fine red tint. It is remarkable for the magnificent blue colour it communicates to glass, and by this character its presence may be readily detected before the blowpipe; the substance to be examined being fused with borax on a loop of platinum wire. Used to make blue colours for painters, stains and glazes for enamellers, glass-melters, potters, &c. In _medicine_ it has occasionally been given as a remedy for rheumatism.

2. =Cobalt, Sesquiox'ide of.= Co_{2}O_{3}. _Syn._ PEROX'IDE OF COBALT. A black, insoluble, neutral powder, obtained by mixing solutions of cobalt and of chloride of lime; or, by heating the protoxide to redness in an open vessel.

=Cobalt, Phos'phate of=. Co_{3}(PO_{4})_{2}. _Prep._ As the acetate, substituting phosphoric for acetic acid. An insoluble purple powder, which, when heated along with eight times its weight of gelatinous alumina, produces a blue pigment (COBALT BLUE, COBALT ULTRAMARINE), almost equal in beauty to ultramarine. (See _below_.)

=Cobalt, Sul'phate of.= CoSO_{4}. By boiling sulphuric acid on the metal, or by dissolving the oxide in the acid. It forms reddish crystals, soluble in 24 parts of water.

=Cobalto-Ultramarine.= A fine blue pigment, prepared by mixing freshly precipitated alumina, 8 parts, with phosphate or arseniate of cobalt, 1 part; drying the mixture, and then slowly heating it to redness. By daylight the colour is pure blue, but by artificial light it is violet. See BLUE PIGMENTS.

=COCA. Erythroxylon Coca.= This plant is grown largely in Peru and Bolivia. The Bolivian coca is said to be much superior to the Peruvian. The best kind is believed to come from the province of Yungas, and the most inferior description from Peru. The consumption of Coca in Peru, Bolivia, and in some of the provinces of the Argentine Confederation is enormous. In small doses it is supposed to act as a stimulant and to aid digestion; in large ones it is said to possess dangerous narcotic properties. The mountaineers in South America state they are enabled to reach high elevations without difficulty of respiration, and to stave off the feeling of hunger by chewing the leaves during their ascents. "Good quality coca should have its leaves unbroken, of a medium size, bright green in colour, and of an odour somewhat combining that of hay and chocolate. The taste is bitter, and when masticated, coca is said to yield easily to the teeth. Infused in hot water, it has a beautiful green colour, which, however, is much darker from inferior leaves. An infinite number of varieties are recognised between the best and the lowest quality, which has a disagreeable smell and a colour resembling roasted coffee. The leaves are also bent and broken, scarcely a whole leaf being found amongst them."[249] The statements as to the effects of coca are conflicting, as will be seen from what follows:--Sir R. Christison, writing to the 'British Medical Journal,' April 29th, 1876, states he was hardly sensible of the fatigue of two mountain descents made from Ben Vorlich after chewing coca leaves. That, as a consequence of his doing so, hunger and thirst were suspended for a long time, but that eventually appetite and digestion were unaffected. He made trial during the first descent of 60 grains, and of the second, undertaken eight days after, of 90 grains of coca.

[Footnote 249: 'Pharmaceutical Journal.']

Mr Dowdeswell, in a communication to the 'Lancet,' May 6th, 1876, says that, contrary to the experience of Sir R. Christison, he found no decided effects produced after consuming nearly a pound of the leaves, which were taken in all forms and at all hours for nearly a month. They failed to produce the slightest excitement, not giving rise even to the feeling of buoyancy and exhilaration which is experienced from mountain air or a draught of spring water.

In the 'Canadian Pharmaceutical Journal' for August, 1877, there is a paper by Mr Shuttleworth, wherein results the opposite to those of the last-named gentlemen are recorded. Mr Shuttleworth states that the members of a club established at Toronto for the purpose of playing at La Crosse, a very violent and fatiguing pastime, were almost unanimous in ascribing their invariable success over their numerous adversaries to the use of coca leaves during their contests; their opponents not employing the plant. The antagonists of the club were men of stronger build and physique as well as more accustomed to out-of-door pursuits, and were besides trained players.

The same writer says that in South America care is taken to procure the leaves in as fresh a state as possible, and that many writers have ascribed the want of effect to old leaves.

The 'British Medical Journal' of March 10th, 1877, contains a communication from Dr T. McBean, who states that he has found the administration of coca leaves useful in typhoid fever, as well as in other febrile diseases.

=CO'COA= (k[=o]'-ko). _Syn._ CACA'O. An alimentary substance formed of the roasted seeds of the _Theobroma Cacao_, a tree belonging to the natural order _Byttneriaceæ_. This definition is equally applicable to chocolate, but we commonly class the preparations containing sugar and flavouring substances under that head, and the unsweetened and cheap preparations under COCOA. The cocoa-seed or berry must not be confounded with the cocoa-nut, which is the fruit of a palm (_Cocus nucifera_). The cocoa tree is a native of Mexico, and is now more or less extensively grown throughout Central America, Brazil, Peru, Venezuela, Caraccas, Ecuador, Grenada, Demerara, Essequibo, Guayaquil, and Surinam; with some of the West India Islands, foremost among which stands Trinidad. It has also been introduced with more or less success into Africa, the Mauritius, Madagascar, Bourbon, the East Indies, Australia, and the Philippine Islands. The following is a list of the principal kinds of cocoa, in the order of their commercial value:--Caraccas, Surinam, Trinidad, Grenada, Jamaica, Dominica, Guayaquil, Venezuela, Bahia, Brazil, St. Lucia. It seems probable that some of the highest kinds of cocoa do not find their way into this country, but are consumed by the inhabitants of Spain.

_Prep._ The pods containing the seeds are gathered when ripe, and after having lain for a day and a night are opened, and the seeds, which are taken out by hand, are submitted to what is termed the sweating process. They are first placed on a sloping floor or in baskets, so that the chief part of the pulp in which they are enveloped may drain off, and are then shut up in a close box, and left for 24 to 48 hours, according to the season and weather, after which they are turned out in the sun to dry. Upon a nice performance of the sweating process, which may be likened to malting, the value of the cocoa greatly depends. When quite dry, the seeds are packed in barrels or bags, and are ready for shipment. The process of roasting is effected in a metal cylinder, with holes at each end, through which the vapour generated is allowed to escape. When the aroma is sufficiently developed the seeds are cooled, and then passed to a 'kibling mill,' which removes the husks and skins from the 'nibs' (see _below_).

_Prop., Constituents, &c._ Cocoa, when unadulterated, forms a wholesome and highly nutritious beverage. Its active principle is theobromine, an alkaloid greatly resembling caffeine, the active principle of coffee and tea. A peculiar concrete oil, called cocoa-butter, or, more correctly, butter of cacao, is another important constituent, forming more than half the weight of the seed. The presence of about 20% of albumen gives to cocoa its nutritive character.

_Average composition of cocoa seeds._--(Wanklyn.)

+-------------------------------+-----------+
| | Per cent. |
| Fat (cocoa butter) | 50·00 |
| Albumen, fibrine, and gluten | 18·00 |
| Starch | 10·00 |
| Gum | 8·00 |
| Colouring matter | 2·60 |
| Water | 6·00 |
| Theobromine | 1·50 |
| Ash | 3·60 |
| Loss | 0·30 |
+-------------------------------+-----------+
| | 100·00 |
+-------------------------------+-----------+

Dr Letheby calculated that a pint of cocoa made with 1 oz. of ground nibs would contain the following proportions of nutritious matters:--

+-------------------------------+--------------+
| Nitrogenous matters | 96·2 grains |
| Patty matter | 218·8 " |
| Gum, sugar, and extractive | 65·6 " |
| Mineral matters | 17·5 " |
+-------------------------------+--------------+
| Total extracted | 398·1 |
+-------------------------------+--------------+

_Adult._ Much of the cheap stuff sold as genuine cocoa is shamefully adulterated. Out of 68 samples of cocoa and chocolate examined by the 'Lancet' commission, 39 contained coloured earthy substances, as reddle, Venetian red, umber, &c. To some, chalk or plaster of Paris had been added, for the purpose of increasing the weight. Many of the samples consisted of sugar and starch, with only sufficient cocoa to impart a flavour. Cocoas containing a moderate amount of arrow-root or other starch must not be considered adulterated articles, for it is impossible to render cocoa soluble, or rather emulsive, without the addition of some diffusible substance.

By an examination of the ash the presence of any mineral adulterant may be detected. Mr Blyth says the amounts of ash in genuine cocoa should never exceed 5 per cent. The seed of the cocoa consists of husk and seed proper. Under the microscope the husk exhibits on its surface a number of tubular fibres, filled with granular matter and minute corpuscles. It consists of three membranes; the first being a single layer of elongated cells; the second (forming the chief portion of the husk) of angular cells, enclosing mucilage, and also containing a few spiral vessels and woody fibres. The third membrane is very thin and delicate, and is made up of small angular cells containing minute globules of fat. The seed is composed of minute cells containing starch. The starch corpuscles are very small, with a trace of inulin. (See cuts on previous page.)

=Cocoa, Flake.= This is formed by grinding the nibs in a mill, consisting of two cones, working one inside the other. Pure flake cocoa is not a diluted or amalgamated article; in other words, it contains no sugar, and but a trace of starch.

=Cocoa Nibs.= The bruised, roasted seeds, freed from husk and membrane. They ought to be of a dull-red or greyish colour, but are frequently given a bright-red colour by a coating of Venetian red.

=Cocoa, Sol'uble.= From cocoa nibs and substances which are readily soluble or diffusible in water, ground together. Sugar and sago or arrow-root are the diluents used by respectable makers, but all kinds of starches, coloured with Venetian red, are used for the trashy articles which are sold to the poor. No form of cocoa is really soluble, but by the addition of easily diffusible substances an article is produced which is capable of forming an emulsion with boiling water. The following are the principal varieties of the so-called soluble cocoa:--

1. COCOA, GRANULATED. From cocoa nibs and sufficient sugar and arrow-root to keep the fatty particles from forming a pasty mass. As it is impossible to granulate the nibs without the admixture of some other substance, those makers who declare that their granulated cocoas are perfectly pure do not act honestly towards their customers.

2. COCOA, HOM[OE]OPATHIC. A kind of soluble cocoa prepared with arrow-root, but without sugar.

3. COCOA, ICELAND-MOSS. From cocoa and Iceland moss, freed from its bitter principle, cetrarine. This form of cocoa was introduced by Messrs Dunn and Hewett, and is said to form a very valuable article of diet for invalids.

4. COCOA, MARAVILLA. This is stated to be "the perfection of prepared cocoa." It consists of cocoa, sugar, and sago flour, the last two being in great excess.

5. COCOA, CARACCAS. This is similar to the last, being a mixture of cocoa, sugar, and sago flour. The cocoa used in its manufacture is said to be imported from the Caraccas, on the north coast of South America, and to possess a peculiarly delicious flavour.

The amount of flour or starch in these so-called soluble cocoas frequently exceeds 40 per cent., and the amount of sugar 20 per cent. They have been not inaptly called "soups."

Within the past year or two a new variety of soluble cocoa has been brought into the market. It is sold under various names, thus, 'Theobromine, or Concentrated Cocoa,' 'Cocoa Essence,' 'Cocoatina,' &c. We have examined many of these varieties, and find them to consist of pure cocoa deprived of about two thirds of its fat. It appears very suitable for people of weak digestion.

_Obs._ No warm drink that we take approaches cocoa in its nutritive character, because, while performing to a certain extent the exhilarating work of coffee or tea, it presents to the stomach a very considerable quantity of nitrogenous and carbonaceous matter; this advantage is partly due to the fact that cocoa is taken in the form of an emulsion, instead of an infusion or decoction.

COCOA FOR THE TABLE is readily prepared from the soluble varieties by simply pouring boiling water upon the powder. From cocoa nibs, or flaked cocoa, the beverage is prepared by first pouring boiling water upon them, and then allowing the mass to simmer from 4 to 6 hours. The cocoa must on no account be allowed to boil, for in that case a coagulum will be formed, which cannot be dissolved in water.

=COCOA-NUT OIL.= A species of vegetable butter obtained from the common cocoa nut--the fruit of _Cocos nucifera_, the cocoa palm. It is separated from the dried kernel by hydraulic pressure. It contains olein, and a solid fat often used as a candle material. Large plantations of the cocoa palm, connected with Price's candle company, exist in Ceylon. Cocoa-nut oil is often confounded with cocoa- or cacao-butter, which is the produce of a very different plant, namely, _Theobroma cacao_. See COCINIC ACID, COCOA, STEARIC ACID, &c.

=COC'CULUS IND'ICUS.= _Syn._ INDIAN BERRIES, INDIAN COCKLES, LEVANT NUT, LOUSE GRAINS; BAC'CA ORIENTA'LIS, COCOULUS PISCATOR'IUS, &c., L. The fruit of the _Anamirta paniculata_, a shrub which abounds on the sandy shores of Malabar, and several other islands in the Indian Ocean. The kernels should fill at least two thirds of the fruit.

It is a dark, tough, hard, wrinkled berry, about the size of a cherry, and possesses an intensely bitter taste. The berry consists of two parts, the husk and the kernel, the former being hard and difficult to bruise, and the latter soft and containing a large proportion of fatty matter.

_Uses, &c._ Cocculus indicus is poisonous to all animals, and to most vegetables. It is never employed internally in medicine, but an ointment, formed by mixing the powder with lard, has been used to destroy pediculi and in porrigo. Its active principle is picrotoxin, a peculiar needle-shaped, crystalline substance, possessing all the poisonous properties of the berry in an exalted degree, and of which it contains about 2 per cent. Its effects on the system are, to produce giddiness, convulsions, and insensibility, frequently ending in death. A small portion of the cocculus indicus imported is used by poachers, and a still smaller quantity to destroy vermin, the remaining, and by far the greater part, being employed to adulterate beer and even wine. "In our own analytical experience we have seldom found this substance in beer purchased from a respectable house. We have detected it, however, in beers purchased in the lowest localities in London and elsewhere, but have every reason to suspect that the adulterants had been added by the publican himself, in the form of an extract known in the trade by the name of 'B. E,' or black extract." (Harkness.)

Chemists and druggists are liable to severe penalties if they are found supplying cocculus indicus, or any extract of the same, to brewers or publicans. See BEER, PORTER, &c.

=COCH'INEAL.= _Syn._ COC'CUS (B. P.), L. GRANA FINA, Span. The _Coccus Cacti_ (Linn.), an insect found upon the cactuses of Mexico. It is of great value as a dye stuff. The female insects, when matured, are brushed off the plants and dried by artificial heat. The entire insect is used. There are two varieties known in commerce--silver cochineal, which has a purplish-grey or silver-grey colour; and black cochineal, which is smaller, and of a reddish or purplish-black colour. The former is that commonly met with.

_Adult._ Genuine cochineal has the sp. gr. 1·25. It is commonly increased in weight by slightly moistening it with gum-water, and then rouncing it in a bag, first with sulphate of baryta, and then with finely powdered bone-black. In this way its sp. gr. is raised to 1·35, in consequence of being loaded by about 12% of useless foreign matter.

Herr Durwell, a German chemist, states that he found a sample of cochineal adulterated with sulphate of zinc. He thinks the sophistication was probably effected by immersing the cochineal in sulphate of zinc, and then in an alkali, whereby the white pulverulent aspect of the genuine article was imparted, and the weight increased.

The following is a method which has been given for estimating the value of samples of cochineal:--Grind the samples to be tested to a fine powder, weigh out 2 or 2-1/2 grammes, and boil this amount in a capacious narrow-necked flask, with 750 c. c. of water for 1 hour; filter immediately through dry paper filters, and allow it to cool. To test it 50 c. c. are measured in a flask of that capacity, and poured into another flask of about 200 c. c., and the measuring vessel rinsed with a definite quantity of water, say 10 to 15 c. c. A weak solution of permanganate is then run in from a burette with a glass cock, the flask being shaken after the addition of every 10 c. c. So much permanganate solution is then added that the cochineal extract shall be charged from its original colour to a pink of the faintest shade--almost yellow, in fact, but never reaching a full yellow. This pink shade should be persistent, that is, it should not turn yellow after standing fifteen minutes; and after a little practice it will be found very easy to obtain the tinge, which shows that the colouring matter is almost but not quite destroyed.

When a number of samples are to be compared, arrange an equal number of 200 c. c. flasks and test-tubes on the table, a tube standing in its rack in front of each flask. Then the same number of c. c. of the permanganate solution (which should be, at least, so weak that bulk for bulk of this and the cochineal solution will be required) is run into each flask, taking care to use too little to completely destroy the colouring matter in _all_.

The flasks are well shaken and allowed to stand for ten minutes. Part of the contents of each is then poured into the corresponding test-tube, and a glance of the tubes as they stand side by side will show which is the least affected by the bleaching liquid. This sample having been selected to serve as a standard, the contents of the test-tube are returned to the flask, and more permanganate solution is cautiously added, until a very faint pink tinge, which a fraction of a c. c. will turn to a full yellow, is obtained. The number of c. c. used having been noted, a fresh trial is made, in which the c. c. required, minus one, are used, the flask agitated, and the last c. c. or part of it, as the whole may not be necessary added.

If the two results agree, the next sample is treated in the same way, and so until all are tested.

A final trial may be made by measuring 50 c. c. of each solution into its flask, running in the permanganate in the ascertained amount into each as quickly as possible, letting the flasks stand ten minutes, and then making a comparison of all in the test-tubes. If the shades are not exactly alike, a pretty good guess can generally be made of the fractions of c. c. required, which should be added, the contents of the tubes being joined to that in the flasks, and a second or third comparison thus made.

This is a rather long description of what is in practice a very simple and good process, the three principal points to be borne in mind being--

1st. To use a weak solution of permanganate.

2nd. To have a very faint pink colour as a standard of comparison.

3rd. To let the liquids remain after agitation together ten or fifteen minutes before comparing them.

_Uses, &c._ Cochineal is principally used to prepare lake and carmine, and in dyeing. Its colouring principle is freely soluble in water. It imparts every variety of scarlet and crimson to textile fabrics previously prepared with alum, tin, and other mordants. It is also used to colour liqueurs, tinctures, and confectionery. It has been recommended as an antispasmodic and anodyne, in hooping-cough and neuralgia.--_Dose_, 10 to 60 gr., in powder, confection, or tincture. See CARMINE and CARMINIC ACID.

=COCIN'IC ACID.= _Syn._ COCOSTEAR'IC ACID. A crystalline, fatty acid, obtained by the saponification of COCOA-NUT OIL. See STEARIC ACID.

=COCK-METAL.= _Syn._ POT METAL. Copper, 20 lbs.; lead, 8 lbs.; litharge, 1 oz.; antimony, 3 oz. Another variety consists of copper, lead, and sometimes a little zinc.

=COCKROACH.= See BLATTA.

=COD.= _Syn._ GA'DUS MOR'RHUA (Ph. L.), MOR'RHUA VULGARIS (Linn.), ASEL'LUS (Pliny), L. A fish common in the seas of the northern hemisphere, from about 40° to 75° of latitude. The flesh forms a most wholesome and excellent article of food. The best fish are very thick about the neck; and, when fresh, are marked by the redness of the gills, freshness of the eyes, and the whiteness and firmness of the flesh. The fish so largely imported from Newfoundland (NEWFOUNDLAND FISH) are cod beheaded, split open, gutted, and salted. They are caught by millions on the 'Grand Bank.' COD-SOUNDS are pickled in brine and also made into isinglass. The spawn is made into CAVIARE, and the liver is both pressed and boiled for its oil (see _below_).

COD IS GENERALLY COOKED by boiling it, but is sometimes baked, or cut into slices and broiled or fried. Cod's head and shoulders with oyster sauce is a favorite dish. Shrimp and anchovy sauce are also good additions.

=COD-LIV'ER OIL.= _Syn._ MOR'RHUÆ O'LEUM, B. P.; O'LEUM JECOR'IS ASEL'LI, L.; HUILE DE MORUE, Fr. The oil obtained from the liver of the common cod (_oleum e jecore comparatum_).

_Prep._ 1. The livers, being removed from the fish, are piled on layers of fir-twigs placed in tubs perforated at the bottom, and are allowed to remain for a considerable time exposed to the sun and air. As the livers putrefy, the oil runs out and flows through the holes in the tubs into vessels placed to receive it.

2. The partially decomposed livers, cut into pieces, are heated in iron pots without water, and the oil is poured off and set aside to deposit impurities.

3. (Savory.) The livers taken from the fresh fish are carefully washed. The large veins are then divided through their whole length, and any blood in them is carefully rinsed away. The livers are now cut into pieces, again washed and drained, and afterwards placed with a small quantity of water in vessels gently heated by steam. As the heat increases, the oil separates and rises to the surface, from which it is skimmed off; and after well cooling, to allow the deposit of some of the margarin, it is repeatedly filtered through flannel bags and finally through paper. This process gives a fine, clear, straw-coloured oil, having but a slight smell and taste.

4. (Donovan.) The perfectly fresh livers are placed in a metallic vessel and heated with constant stirring to 180° Fahr., by which treatment they break down into a uniform pulpy, liquid mass. This mass is immediately transferred to calico bags, whence the oil drains out; after filtration, while still warm, this oil is sufficiently pure for use.

_Obs._ Three kinds of cod-liver oil are usually distinguished--the pale yellow, pale brown, and dark brown. The latter is the most impure; its odour and taste are extremely disagreeable. The most conflicting opinions have been expressed by medical men as to the relative value of the light brown and yellow varieties. Ozonised cod-liver oil is said to be prepared by passing oxygen into the oil, and then exposing it to sunlight. Dr Letheby applied the most delicate tests to this much-vaunted remedy, but was not able to detect the slightest trace of ozone.