Chapter LXXV: Part 2 (36)

=TAPS, WOODEN (to prevent their cracking).= The taps are placed in mother paraffin, heated to from 110° to 120°; by this means the water is eliminated from the wood, and the wood becomes thoroughly impregnated with paraffin. The taps are heated in this bath until all the aqueous vapour has been expelled, and are left in it, after the removal of the vessel from the fire, up to the very moment the paraffin begins to solidify. Wooden taps thus prepared are very durable, do not become soaked with liquids, keep very tight, and are not liable to become mouldy. The excess of paraffin is wiped off with care, and the taps are next rubbed clean with a piece of flannel. (Dr E. Kopp.)[224]

[Footnote 224: ‘Chemical News.’]

=TAR.= _Syn._ PIX LIQUIDA (B. P., Ph. L., E., & D.), L. A liquid bitumen prepared from the wood of _Pinus sylvestris_, and other species, by heat. The chemical constitution of tar is very complicated. Its uses in the arts are well known. As a medicine it is stimulant, diuretic, sudorific, and vermifuge.——_Dose_, 20 to 60 minims, made into pills with flour; in ichthyosis, &c. Externally, in lepra, psoriasis, foul ulcers, &c. See OINTMENT and INFUSION.

=Tar, Barbadoes.= _Syn._ PIX LIQUIDA BARBADENSIS, PETROLEUM BARBADENSE, PETROLEUM (Ph. L. and E.), L. “Black liquid bitumen, exuding spontaneously from the earth.” (Ph. L.) Its properties for the most part resemble those of the last.——_Dose_, 10 to 30 drops; in asthma, chronic coughs, tapeworm, &c. Externally, in chilblains, chronic and rheumatic pains, &c. See PETROLEUM.

=Tar, Coal.= Produced during the distillation of bituminous coal for gas. See NAPHTHA, &c.

=TARAX′ACUM.= See DANDELION.

=TAR COLOURS.= _Syn._ COAL TAR COLOURS, ANILINE COLOURS, &c. Coal tar, the source of the aniline colours, consists of the oily fluid obtained in the destructive distillation of coal, during the manufacture of ordinary illuminating gas, and collected in a tank from the hydraulic main and condensers.

The composition of coal tar is highly complex, the most important constituents being, however, a series of homologous hydrocarbons obtained by distilling coal tar, and known as ‘coal naphtha.’ Naphtha, by rectification between 180° and 250° Fahr. (82 and 121 Cent.), yields a light yellow oily liquid, of sp. gr. ·88, the benzol of commerce.

By the action of a mixture of nitric and sulphuric acids on benzol, nitro-benzol, a heavy oily liquid with an odour of oil of bitter almonds is obtained. In commerce this substance is made in large cast-iron pots, fitted with tight covers, and provided with stirrers worked by steam power. By means of pipes the reagents are admitted and the nitrous fumes are carried off, while the nitro-benzol and the spent reagents are drawn off from the bottom. The entire charge of benzol is first placed into the vessels, and the mixed acids are, as the reaction is very energetic, cautiously run in, the whole being well stirred throughout. When finished, the contents are drawn off, and the nitro-benzol collected, washed with water, and, if necessary, neutralised with a solution of soda. See BENZOL.

Nitro-benzol is converted into aniline in a similar apparatus, only provided with means of admitting a current of superheated steam, and condensing the aniline as it distils over. Into the vessel iron borings are placed, and acetic acid and nitro-benzol cautiously run in as the reduction is violent, stirring well all the time. A current of superheated steam is passed through, and the aniline collected as it distils over as a pale, sherry-coloured oily liquid, boiling at 360° Fahr. (182 Cent.), and of sp. gr. 1·02. See ANILINE.

MAUVE, INDISINE, VIOLINE, PHENAMINE, the first-discovered coal tar, or aniline colour, was obtained by Mr Perkins during some experiments directed towards the artificial formation of quinine, and was also first practically manufactured by Mr Perkins. Commercially, mauve is made as follows:

Aniline and sulphuric acid in proper proportions are dissolved in water in a vat by aid of heat, and when cold a solution of bichromate of potassium added, and the whole allowed to stand a day or two, when a black precipitate is obtained, which, after collecting on shallow filters, is washed and well dried. This black resinous substance is digested with dilute methylated spirit in a suitable apparatus, to dissolve out the mauve, and the major portion of the spirit distilled off. The mauve is precipitated from the aqueous solution left behind by hydrate of sodium, and after washing is either drained to a paste or dried.

The amount of mauve thus obtained is but small in comparison with the raw material, coal tar, as 100 lbs. of coal yield 10 lbs. 12 oz. of coal tar; 8-1/2 oz. of mineral naphtha, 2-3/4 oz. of benzol; 4-1/4 oz. of nitro-benzol, 2-1/4 oz. of aniline, and 1/4 oz. of mauve. Mauve is usually sent into the market in paste or solution, the expense of the crystals being heavy, and offering no corresponding advantages.

Other salts than the bichromate of potassium have been employed to convert aniline into mauve, as chloride of copper, permanganate of potassium, &c.; but experience has shown none to possess the same advantages as the bichromate of potassium.

MAUVEINE, the organic base of mauve or aniline purple, is a black crystalline powder, of the formula C_{27}H_{24}N_{3}, yielding a dull violet solution. The moment, however, mauveine is brought in contact with an acid, it turns a magnificent purple colour. The salts of mauveine form beautiful crystals possessing a splendid green metallic lustre, soluble very readily in alcohol, and less so in water. The commercial salt, or mauve, is the acetate, or sometimes the hydrochlorate.

=Magenta.= _Syn._ ANILINE RED, ROSEINE, FUCHSINE, AZALEINE, SOLFERINO, TYRALINE. Various processes have been proposed and patented for the preparation of this commercially important coal-tar colour. Amongst these processes are——

1. Gerber-Keller’s, patented in France, October 29th, 1859. By this the aniline is treated with mercuric nitrate.

2. Lauth and Depouilly used nitric acid.

3. Medlock (patent dated January, 1860). Nicholson, and Messrs Girard and De Laire, all in 1860, separately patented the use of arsenic acid. This process, being the one now almost exclusively employed, is thus described in Crace Calvert’s work, ‘Dyeing and Calico Printing,’ edited by Messrs Stenhouse and Grove. “The manufacture of magenta, as it is now conducted in the large colour works, is a comparatively simple process, the apparatus employed consisting of a large cast-iron pot set in a furnace, provided with means of carefully regulating the heat. It is furnished with a stirrer, which can be worked by hand or by mechanical means, the gearing for the stirrer being fixed to the lid, so that by means of a crane the lid may be removed, together with the stirrer and gearing. There is also a bent tube passing through the lid for the exit of the vapours, which can be easily connected or disconnected with a worm at pleasure; lastly, there are large openings at the bottom of the pot, closed by suitable stoppers, so that the charge can be removed with facility as soon as the reaction is complete. Into this apparatus, which is capable of holding about 500 gallons, a charge of 2740 lbs. of a concentrated solution of arsenic acid, containing 72% of the anhydrous acid, is introduced, together with 1600 lbs. of commercial aniline. The aniline selected for this purpose should contain about 25% of the toluidine.

“After the materials have been thoroughly mixed by the stirrer the fire is lighted, and the temperature gradually raised to about 360° F. In a short time water begins to distil, then aniline makes its appearance along with the water, and, lastly, aniline alone comes over, which is nearly pure, containing, as it does, but a very small per centage of toluidine. The operation usually lasts about eight or ten hours, during which time about 170 gallons of liquid pass over, and are condensed in the worm attached to the apparatus; of this about 150 lbs. are aniline. The temperature should not exceed 380° F. at any period during the operation. When this is complete steam is blown in through a tube, in order to sweep out the last traces of the free aniline, and boiling water is gradually introduced in quantity sufficient to convert the contents into a homogenous liquid. When this occurs the liquid is run out of the openings at the bottom into cisterns provided with agitators; here more boiling water is added, in the proportion of 300 galls. to every 600 lbs. of crude magenta, and also 6 lbs. of hydrochloric acid. The mass is then boiled for four or five hours by means of steam pipes, the agitators being kept in constant motion. The solution of hydrochloride, arsenite, and arseniate of rosaniline thus obtained is filtered through woollen cloth, and 720 lbs. of common salt added to the liquid (which is kept boiling) for each 600 lbs. of crude magenta. By this means the whole of the rosaniline is converted into hydrochloride, which, being nearly insoluble in the strong solution of arseniate and arsenite of sodium produced in the double decomposition, separates and rises to the surface; a further quantity is deposited from the saline solution on allowing it to cool and stand for some time. In order to purify the crude rosaniline hydrochloride it is washed with a small quantity of water, redissolved in boiling water slightly acidulated with hydrochloric acid, filtered, and allowed to crystallise.”

If in the treatment of aniline with arsenic acid the latter be considerably beyond the proportion of aniline employed, VIOLET and BLUE dyes may be formed. The production of such has been patented by Girard and De Laire.

4. Laurent and Casthélaz have obtained aniline red direct from benzol, without the preliminary isolation of aniline. Nitrobenzol is treated with twice its weight of iron finely divided, and half its weight of concentrated hydrochloric acid. The colouring matter obtained by this process is said to be inferior in beauty to that procured from aniline.

5. Messrs Renard Brothers include in their patent the ebullition of aniline with stannous, stannic, mercurous, and mercuric sulphates, with ferric and uranic nitrates and nitrate of silver, and with stannic and mercuric bromides.

6. Messrs Dale and Curo’s (patent dated 1860) consists in the treatment of aniline or hydrochlorate of aniline with nitrate of lead.

7. Mr Smith claims the ebullition of aniline with perchloride of antimony, or the action of antimonic acid, peroxide of bismuth, stannic, ferric, mercuric, and cupric oxides, upon hydrochlorate or sulphate of aniline, at the temperature of 180°.

Coupier’s process for the manufacture of magenta without the use of arsenic acid is as follows:——He heats together pure aniline, nitrotoluene, hydrochloric acid, and a small quantity of finely-divided metallic iron, to a temperature of about 400° F. for several hours. The pasty mixture soon solidifies to a friable mass resembling crude aniline red——ordinary commercial aniline. The above processes are for the preparation of crude aniline red only. The crude colours contain some undecomposed aniline, mostly in the form of salts. They are also contaminated with tarry matters, some insoluble in water and dilute acids; others soluble in bisulphide of carbon, naphtha, or in caustic or carbonated alkalies. If, therefore, the crude red be boiled with an excess of alkali the undecomposed aniline is expelled, the acid which exists in the product being fixed. On treating the residue with acidulated boiling water the red is dissolved, while certain tarry matters remain insoluble. If now the boiling solution be filtered, and then saturated with an alkali, the colouring matter is precipitated in a tolerable state of purity. By redissolving the precipitated red in an acid, not employed in excess, a solution is obtained which frequently crystallises, or from which a pure red may be thrown down by a new addition of chloride of sodium or other alkaline salt.

Dr Hofmann and Mr Nicholson have demonstrated that pure aniline, from whatever source obtained, is incapable of furnishing a red dye, but that it does so when mixed with its homologue toluidine——toluidine by itself being equally incapable of yielding it. From this it will be evident that an aniline rich in toluidine is an essential condition for obtaining aniline red.

Magenta consists of brilliant large crystals, having a beautiful golden-green metallic lustre, and soluble in water to an intense purplish-red solution. It is a salt of a colourless base, rosaniline, which is prepared from magenta by boiling with hydrate of potassium, and allowing the solution to cool, when it crystallises out in colourless crystals, having the formula C_{20}H_{19}N_{3}H_{2}O. All the salts of rosaniline have a splendid purple-red colour, and that usually met with as magenta is the hydrochlorate, although the nitrate, oxalate, and acetate are also to be obtained.

Sugar, previously dyed with magenta, is sometimes used as an adulterant of crystallised magenta. If present, the larger crystals of dyed sugar may be readily detected by their colour being paler at the edges, when the suspected sample is spread out on a sheet of white paper in the sunshine. One of the best methods of testing magenta is to make a comparative dyeing experiment with the sample under examination, and with one of known purity, using white woollen yarn.

From magenta or hydrochlorate of rosaniline a large number of colouring matters are produced, the most important of which will be briefly described below.

ANILINE BLACK. “Dissolve 20 parts of potassium chlorate, 40 parts of sulphate of copper, 16 parts of chloride of ammonium, and 40 parts of aniline hydrochloride, in 500 parts of water, warming the liquid to about 60°, and then removing it from the water bath. In about three minutes the solution froths up and gives off vapours which strongly attack the breathing organs. If the mass does not become quite black after the lapse of a few hours it is again heated to 60°, and then exposed in an open place for a day or two, and afterwards carefully washed out till no salts are found in the filtrate. For use in printing, the black paste is mixed with a somewhat large quantity of albumen, and the goods after printing are strongly steamed. The paste can be pressed into moulds, and used as a substitute for Indian ink.” (A. Müller.) “Mix equal weights of aniline (containing toluidine), hydrochloric acid, and potassium chlorate, with a minute quantity of cupric chloride and a sufficient quantity of water, and leave the mixture to evaporate spontaneously, when a black powder will be obtained.” (Rheineck.)

ANILINE BLUE, or BLEU DE LYONS. This dye is prepared by heating a mixture of magenta, acetate of sodium, and aniline in iron pots, provided with stirrers, &c., in an oil bath, to 370° Fahr. (190° C.), and the excess of aniline distilled over. When a good blue has been obtained the heat is removed, and the thick treacly fluid purified. This is effected for the commoner varieties by treating the crude product with hydrochloric acid, to dissolve all the excess of aniline, and the various red and purple impurities; but for the better qualities by mixing the crude product with methylated spirit, and pouring the whole into water acidulated with hydrochloric acid, and then thoroughly washing the colouring matter that is precipitated, with water and drying.

This blue, like magenta, is a salt of a colourless base, which has been named Triphenyl-rosaniline. C_{38}H_{31}N_{3}, or C_{20}H_{16}(C_{6}H_{5})_{3}N_{3}. Aniline blue, or Lyons blue, is sent into the market either as a coarse powder of a coppery lustre, or in alcoholic solution; as it is insoluble in water, which necessitates it being added to the dye bath in solution in spirit, a great drawback.

Mr Nicholson, by treating Lyons blue in the same manner as indigo is converted into sulphindigotic acid, has succeeded in rendering it soluble; dissolving in alkalies to form colourless salts, and decomposed by acids into its original blue colour.

By a modification of this method ‘NICHOLSON’S BLUE’ is prepared, a fine soluble blue dye. Another colouring matter called Paris blue or bleu de Paris was obtained by heating stannic chloride with aniline for 30 hours at a temperature of 356° Fahr. (180 C.). It is a fine pure blue, soluble in water, and crystallising in large blue needles with a coppery lustre.

Another method pursued in manufacture of this colour on a large scale is carried out by allowing a mixture of a salt of rosaniline, with an excess of aniline, to digest at a temperature of 150° to 160° for a considerable time. If a mixture of 2 kilogrammes of dry hydrochlorate of rosaniline, and 4 kilogrammes of aniline be employed, the operation is completed in four hours. The crude blue is purified by treating it successively with boiling water, acidulated with hydrochloric acid, and with pure water, until it is of the purest blue colour. ‘Nicholson’s blue’ is obtained by digesting triphenyl rosaniline——mono-sulphonic acid (made by dissolving triphenyl rosaniline hydrochloride in strong sulphuric acid, and heating the solution for five or six hours. On the addition of water, the acid is obtained as a dark blue precipitate, and dried at 100°), with a quantity of soda-lye not quite sufficient for saturation, filtering the solution and evaporating. It is dried at 100°. Wool dipped into a hot aqueous solution of Nicholson’s blue, especially if borax or water-glass be added, extracts it in a colourless state, and holds it so fast that it cannot be washed out with water, but on dipping the wool thus prepared into an acid the salt is decomposed, and the colouring matter is set free.

ANILINE BLUE FOR PRINTING. Blumer-Zweefel gives the following process:——“Mix 100 parts of starch with 1000 parts of water, and add to it while warm 40 parts of potassium chlorate, 3 to 4 parts of ferrous sulphate, and 10 parts of sal ammoniac. The well-mixed paste, when quite cold, is mixed with 70 parts of aniline hydrochloride, or an equivalent quantity of tartrate, and immediately used. The printed goods are oxidised, then passed through warm or faintly alkaline water, whereby the blue colour is developed.”

VIOLET IMPERIAL. If the action of the aniline and magenta in the process of manufacturing aniline blue be stopped before it is finished, and the resulting product treated with dilute acid, a colouring matter called violet imperial is obtained. It is now, however, replaced by the Hofmann violets.

Mr Nicholson obtains another violet from aniline red, by heating it in a suitable apparatus to a temperature between 200° and 215° C. The resulting mass is exhausted with acetic acid, and the deep-violet solution diluted with enough alcohol to give the dye a convenient strength. Aniline violet, although it resists the action of light to a very considerable extent, has been shown by Chevreul to be inferior in this particular than either madder, cochineal, or indigo.

HOFMANN VIOLETS. On a large scale these violets are produced in deep cast-iron pots, surrounded by a steam jacket, and provided with a lid, having a perforation for distilling over the excess of reagents.

These vessels are charged with a solution of magenta in methylated or wood spirit, and iodide of ethyl or methyl, in proportions according to the shade required, and the whole heated by steam for five or six hours, when the excess of alcohol and iodide of ethyl is distilled over. The resulting product is dissolved in water, filtered, precipitated with common salt, and well washed.

Like most of the other colours, Hofmann violets are salts of colourless bases. That of a red shade has a formula of C_{22}H_{23}N_{3}, or C_{20}H_{18}(C_{2}H_{5})N_{3}; of a true violet shade C_{24}H_{27}N_{3}, or C_{20}H_{17}(C_{2}H_{5})_{2}N_{2}; and of a blue shade of violet, of C_{26}H_{31}N_{3}, or C_{20}H_{16}(C_{2}H_{5})_{3}N_{3}. They are all moderately fast on wool and silk, although less so on cotton, and, as they can be produced in nearly every shade of violet, are in great use, having replaced most of the other violets.

The following processes have also been proposed for the production of aniline violet:

1. Oxidation of an aniline salt by means of a solution of permanganate of potassium. (Williams.)

2. Oxidation of an aniline salt by means of a solution of ferricyanide of potassium. (Smith.)

3. Oxidation of a cold and dilute solution of hydrochlorate of aniline, by means of a dilute solution of chloride of lime. (Bolley, Beale, and Kirkmann.)

4. Oxidation of a salt of aniline by means of peroxide of lead under the influence of an acid. (Price.)

5. Oxidation of a salt of aniline in an aqueous solution of peroxide of manganese. (Kay.)

6. Oxidation of a salt of aniline by free chlorine or free hypochlorous acid. (Smith.)

DAHLIA. This is prepared from mauve and iodide of ethyl, in the same manner as the Hofmann violets, and is a purple-red violet. It is a good colour, but the expense precludes its general use.

BRITANNIA VIOLET. This is obtained in the same manner as the Hofmann violets, by acting on an alcoholic solution of magenta, with a thick, viscid, oily fluid of the formula C_{10}H_{15}Br_{3}, obtained by cautiously acting with bromine on oil of turpentine. It is a beautiful violet, capable of being manufactured of every shade, from purple to blue, and most extensively used.

ALDEHYDE GREEN. Prepared by dissolving one part of magenta in three parts of sulphuric acid, diluted with one part of water, adding by degrees one and a half part of aldehyde, and heating the whole on a water bath until a drop put in water turns a fine blue. It is then poured into a large quantity of hot water containing three parts of hyposulphite of sodium, boiled and filtered. The filtrate contains the green, which can either be kept in solution or be precipitated by means of tannic acid or acetate of sodium. Like the other colours, this green is a salt of a colourless base, containing sulphur, the formula of which is not known, and is principally used for dyeing silk, being very brilliant in both day and artificial light.

IODIDE GREEN. Produced during the manufacture of the Hofmann colours, and is now used for dyeing cotton and silk; its colour being bluer than that of aldehyde green, it is more useful. Iodide green, not being precipitated by carbonate of sodium, is usually sold in alcoholic solution.

PERKINS GREEN. This is also a magenta derivative, and a salt of a powerful colourless base. It resembles the iodide green, but is precipitated by alkaline carbonates and picric acid. This colour is used chiefly for calico printing, and is quite as fast as the Hofmann colours.

ANILINE GREEN. When treated with chlorate of potassium, to which a quantity of hydrochloric acid has been added, aniline assumes a rich indigo-blue colour. The same result occurs if the aniline be treated with a solution of chlorous acid. Similar blues have been obtained by Messrs Crace Calvert, Lowe, and Clift. Most of these blues possess the property, when subjected to the action of acids, of acquiring a green tint, called EMERALDINE. Dr Calvert obtained this colour directly upon cloth, by printing with a mixture of an aniline salt and chlorate of potassium, and allowing it to dry. In about twelve hours the green colour is developed. This colour may be converted into blue by being passed through a hot dilute alkaline solution, or through a bath of boiling soap.

ANILINE YELLOW. Amongst the secondary products obtained during the preparation of aniline red, there occurs a well-defined base of a splendid yellow colour, to which the name _chrysaniline_ has been given. It is prepared by submitting the residue, from which the rosaniline has been extracted, to a current of steam for some time, when a quantity of the chrysaniline passes into solution. By adding nitric acid to the solution, the chrysaniline is thrown down in the form of a difficultly soluble nitrate. The intimate relation between chrysaniline, rosaniline, and leucaniline has been shown by Hofmann.

Chrysaniline C_{20}H_{17}N_{3}.
Rosaniline C_{20}H_{19}N_{3}.
Leucaniline C_{20}H_{21}N_{3}.

SAFFRANINE. This dye stuff is of a bright red-rose colour. Mené says it may be prepared commercially by treatment of heavy aniline oils successively with nitrous and arsenic acids; or two parts of the aniline may be heated with one of arsenic acid, and one of an alkaline nitrate for a short time, to 200° or 212° F. The product is extracted with boiling water, neutralised with an alkali, filtered, and the colour thrown down by common salt.

Besides the above products obtained from aniline, a series of colours have been obtained from phenol, or carbolic acid, another substance obtained from coal tar.

PICRIC ACID. This is obtained by treating in a suitable apparatus, with proper precautions, carbolic acid with nitric acid. It is a pale yellow crystalline acid, forming dark orange explosive salts, and dyeing silk a fine yellow.

ISOPURPURATE OF POTASSIUM. GRENATE BROWN. GRENATE SOLUBLE. By treating picric acid with cyanide of potassium a very explosive salt is obtained, used to dye wool a dark maroon colour.

AURINE, or ROSOLIC ACID. This is obtained by heating a mixture of sulphuric, oxalic, and carbolic acids, and purifying the products. It is a beautiful reddish, resinous substance, with a pale green lustre, and yielding an orange coloured solution, changed by alkalies to a splendid crimson. Owing to the difficulty in using it, however, it is not very extensively employed.

PEONINE, or CORALLINE. This dye is formed when rosolic acid and ammonia are heated to between 248° and 284° Fahr. (120° to 140° C.). It is a fine crimson dye, forming shades similar to safflower on silk, but, owing to the bad effects of acids, not much used.

AZULINE. Prepared by heating coralline and aniline together. A coppery coloured resinous substance, soluble, in alcohol, and with difficulty in water, and dyeing silk a blue colour. The aniline blues, however, have superseded it to a great extent.

There are other substances obtained from coal tar that have been employed to form dyes, but of which we shall only refer to one——naphthaline. By treating this in exactly the same manner as benzol, it is converted into aniline. A solid crystalline white base, termed naphthylamine, is produced. From this substance is obtained the following dye.

DINITRONAPHTHAL, or MANCHESTER YELLOW. Naphthylamine is converted into diazynaphthol by treatment with nitrate of potassium, and the latter, when heated with nitric acid, yields the colour. It is a weak acid, and the salt employed in commerce is the beautiful yellow crystalline calcium salt which dyes silk and wool a magnificent golden-yellow colour.

=TARPAU′LIN.= _Syn._ TARPAWLING. Canvas covered with tar or any composition to render it waterproof.

=TAR′RAS.= _Syn._ TERRAS. A volcanic product resembling puzzolano, that imparts to mortar the property of hardening under water. Several other argillo-ferruginous minerals possess the same power, and are used under this term.

=TAR′TAR.= _Syn._ ARGAL, ORGOL; TARTARUM, TARTARUS, L. Impure bitartrate of potassa. Crude tartar is the concrete deposit formed upon the sides of the casks and vats during the fermentation of grape juice. That obtained from white wine is white argol; that from red wine, red argol. After purification it forms cream of tartar.

=Tartar, Ammo′′niated.= _Syn._ AMMONIO-TARTRATE OF POTASSA, SOLUBLE TARTAR (Ammoniated); TARTARUS AMMONIATUS, TARTARUM SOLUBILE AMMONIATUM, L. _Prep._ Neutralise a solution of cream of tartar with ammonia in slight excess, then evaporate, and crystallise. Very soluble in water. A favourite laxative on the Continent.

=Tartar, Bo′′raxated.= _Syn._ SOLUBLE CREAM OF TARTAR, BORO-TARTRATE OF POTASSA AND SODA; TARTARUM BORAXATUM, CREMOR TARTARI SOLUBILIS, POTASSÆ ET SODÆ TARTRAS BORAXATA, L. _Prep._ From borax, 2 lbs; cream of tartar, 5 lbs. (both in powder); dissolved in water, evaporated, and crystallised. See POTASSIUM BOROTARTRATE.

=Tartar, Chalybea′ted.= Potassio-tartrate of iron.

=Tartar, Cream of.= Bitartrate of potassa.

=Tartar, Emet′ic.= Potassio-tartrate of antimony.

=Tartar, Oil of.= Deliquesced carbonate of potassa.

=Tartar, Reduced.= _Syn._ CREMOR TARTARI REDUCTUS, L. An article is sold, under the name of ‘British cream of tartar,’ which contains 1/4 its weight or more of bisulphate of potassa.

=Tartar, Salt of.= Carbonate of potassa.

=Tartar, Sol′uble.= Neutral tartrate of potassa.

=Tartar, Spirit of.= Pyrotartaric acid.

=TARTAR′IC ACID.= H_{2}C_{4}H_{4}O_{6}. _Syn._ ACID OF TARTAR, ESSENTIAL SALT OF T.†; ACIDUM TARTARICUM (B. P., Ph. L., E., & D.), SAL ESSENTIALE TARTARI†, L. _Prep._ 1. (Ph. L. 1836.) Take of cream of tartar, 4 lbs.; boiling water, 2 gall.; dissolve by boiling; add, gradually, of prepared chalk, 12 oz. 7 dr. (made into a milk with water), and, when the effervescence ceases, add another like portion of prepared chalk, dissolved in hydrochloric acid, 26-1/2 fl. oz., or q. s., diluted with water, 4 pints; collect the precipitate (‘tartrate of lime’), and, after well washing it with water, boil it for 15 minutes in dilute sulphuric acid, 7 pints and 17 fl. oz.; next filter, evaporate the filtrate (to the density of 1·38), and set it aside to crystallise; redissolve the crystals in water, concentrate the solution by evaporation, and recrystallise a second and a third time. The Edinburgh formula is nearly similar. In the Ph. L. & D. tartaric acid is placed in the Materia Medica.

2. (Gatty.) The solution of argol or tartar is first neutralised with carbonate of potassa, and to every 300 gall. of the clear liquid, at 5° Twaddell, 34 gall. of milk of lime (1 lb. of lime per gall.) are added; carbonic acid gas is then forced in, with agitation; decomposition ensues, with the formation of ‘bicarbonate of potassa’ and ‘tartrate of lime,’ the last is converted into tartaric acid in the usual manner, and the former is evaporated in iron pans, and roasted in a reverberatory furnace for its potassa.

_Prop._ Tartaric acid forms inodorous, scarcely transparent, oblique rhombic prisms, more or less modified, which are permanent in the air; it possesses a purely sour taste, dissolves in about 2 parts of water at 60° Fahr., and in about its own weight of boiling water; it is slightly soluble in alcohol; the aqueous solution exhibits right-handed polarisation, and suffers gradual decomposition by age.

It is free from colour; is entirely, or almost entirely, dissipated by ignition; and is entirely soluble in water.

_Tests._ 1. Tartaric acid is known to be such by its solution giving white precipitates with solutions of caustic lime, baryta, and strontia, which dissolve in excess of the acid.——2. A solution of potassa causes a white granular precipitate of cream of tartar, soluble by agitation in excess of the precipitant.——3. Nitrate of silver and acetate of lead give white precipitates, which, when heated, f nine, and yield the pure metal.——4. If to a solution of tartaric acid, or a tartrate, solution of a ferric or aluminum salt be added, and subsequently ammonia or potassa, no precipitate is formed.——5. At about 570° Fahr. all the tartrates are blackened, and yield a peculiar and characteristic odour.

_Uses, &c._ Tartaric acid is chiefly employed in calico printing, and, in medicine, as a substitute for citric acid and lemon juice in the preparation of cooling drinks and saline draughts. For the latter purpose, bicarbonate of soda is the alkaline salt commonly employed.——_Dose_, 10 to 30 grains.

_Concluding Remarks._ On the large scale the decomposition of the tartar is usually effected in a copper boiler, and that of the tartrate of lime in a leaden cistern. This part of the process is often performed by mere digestion for a few days, without the application of heat. Leaden or stoneware vessels are used as crystallisers. Good cream of tartar requires 26% of chalk and 28·5% of dry chloride of calcium for its perfect decomposition. Dry tartrate of lime requires 75% of oil of vitriol to liberate the whole of its tartaric acid. A very slight excess of sulphuric acid may be safely, nay, advantageously, employed. Some manufacturers bleach the coloured solution of the first crystals by treating it with animal charcoal; but for this purpose the latter substance should be first purified by digesting it in hydrochloric acid, and afterwards by edulcorating it with water, and exposing it to a dull red heat in a covered vessel. The general management of this manufacture resembles that of citric acid. To obtain a large product, care must be taken that the whole of the tartrate of lime be thoroughly decomposed, a matter not always effected by clumsy manipulators, who do not adapt their quantities or practice to the circumstances before them.

=TAR′TRATE.= A salt of tartaric acid.

=TARTS.= These may be regarded as miniature pies, consisting of fruit, either fresh or preserved, baked or spread on puff-paste.

=TARTS.= To make an apple tart take about 2 lbs. of apples, peel them, cut each into four pieces, and remove the cores; then let each of the quarters be subdivided into two or three pieces, according to the size of the apple. Having done this, put half the pieces into a pie-dish, press them evenly down, and sprinkle over them two ounces of brown sugar; then add the remaining apples, and afterwards another 2 oz. of sugar, so that the apples shall form a kind of dome, the centre of which is about two inches above the sides, now add a wineglassful of water, and cover the top over with short paste. Let bake in a moderately heated oven from half to three quarters of an hour.

The quantity of sugar must depend upon the quality, and the degree of sweetness, or the reverse, of the apples used. If they are of the sweet kind or very ripe, use less sugar, but a double quantity of water; in the latter case a little of the juice of lemon will improve the flavour. Chopped lemon-peel, or cinnamon, or cloves, may also be added to the tart with advantage.

On making green rhubarb or greengage tarts it will be necessary to use a little more sugar, and to proceed as for apple tart, taking care, however, to omit the lemon juice and peel, cinnamon, or cloves. Tarts of ripe currants, raspberries, cherries, damsons, and mulberries, may be made in the same manner as rhubarb tart. Pink rhubarb does not require peeling.

=TAU′RIN.= C_{2}H_{7}NSO_{3}. Obtained when purified bile is boiled for some hours with an excess of hydrochloric acid. By filtration, evaporation, and dissolving the dry residuum in about 6 parts of boiling alcohol, nearly pure taurin crystallises out as the solution cools. It forms with crystalline needles, which are soluble in water, and sparingly soluble in alcohol. It is remarkable for containing fully 25% of sulphur.

=TAUROCHOLAL′IC ACID.= See CHOLEIC ACID.

=TAW′ING.= In the preparation of the TAWED LEATHER used for gloves, housings, &c., the skins are first soaked, scraped, and hung in a warm room until they begin to exhale an ammoniacal odour, and the wool readily comes off; they are then de-haired, and soaked in water with some quicklime for several weeks, the water being changed two or three times during that period; they are then again beamed, smoothed, and trimmed, after which they are rinsed, and resoaked in a vat of bran-and-water, where they are kept in a state of gentle fermentation for some weeks (in this state they are called ‘pelts’); the skins are next well worked about in a warm solution of alum and salt, again fermented in bran-and-water for a short time, and are then stretched on hooks, and dried in a stove-room; they are, lastly, again soaked in water and trodden or worked in a pail or tub containing some yolks of eggs beaten to a froth with water, after which they are stretched and dried in a loft, and are smoothed with a warm smoothing-iron. Sometimes the process is shortened by soaking the skins in the following mixture after the first steep with bran:——Common salt, 3-1/2 lbs.; alum, 8 lbs.; boiling water, q. s.; dissolve, add of wheaten flour, 21 lbs.; yolks of 9 dozen eggs; make a paste. For use, a portion is to be largely diluted with water.

CHAMOIS or SHAMMY LEATHER is generally prepared from either sheep or doe-skins, which, after dressing, liming, &c., are well oiled on the grain side, then rolled into balls, and thrown into the trough of the fulling-mill, where they are beaten for 2, 3, or 4 hours. They are next aired, and again oiled and fulled, and this is repeated a third time, or oftener, as circumstances may direct. The oiled skins are then exposed to a fermenting process, or heating in a close chamber, and are afterwards freed from redundant oil by being scoured in a weak alkaline lye. They are, lastly, rinsed in clean water, wrung at the peg, dried, and ‘finished’ at the stretcher-iron.

TAWED LEATHER differs from TANNED LEATHER in yielding size or glue under the influence of heat and moisture, in nearly the same way as the raw skins.

=TAXIDERMY, Practical.= The following review on the excellent work on this subject is from ‘The Bazaar,’ ‘Practical Taxidermy; a manual of instruction to the amateur in collecting, preserving, and setting up Natural History Specimens of all kinds. By Montagu Browne.’

“The author of this little book begins at the beginning, and, before detailing the process of skinning, preserving, and mounting any given vertebrate, he starts with a chapter on ‘Trapping and Decoying Birds and Animals.’ In this chapter descriptions are given of various forms of springs, snare, ‘figure-4 trap,’ clap-net, glade-net, bow-net, and box trap; and some wrinkles are imparted which may be useful to wildfowl shooters, to say nothing of gamekeepers, whose livelihood depends on their success in destroying what they are pleased to regard as ‘vermin.’ Chapter 3 is devoted to ‘Necessary Tools,’ of which not only descriptions, but figures are given, and those who have no knowledge of taxidermy will probably be surprised to learn how few tools are really necessary for the purpose.

“On the subject of preservative soaps and powders, Mr Browne has a good deal to say, and gives no less than seventeen different receipts. Many of these, however, are only noticed to be condemned, for the author has been a great experimentalist, and has tested the efficiency or otherwise of all the preparations he names, with a view of ascertaining the best, and at the same time that which is most harmless to the operator. For the preservation of birds he pins his faith to the fourth formula (p. 46), which is a preservative soap for the inside of the skin, composed of 1-1/2 lb. whiting or chalk, 1 lb. of soft soap, and 2 oz. of chloride of lime, finely pounded. These ingredients are boiled together in a pint of water, and the mixture, when properly applied, is said to be so efficacious as to completely supersede arsenical paste or soap. Presuming that it is used only for such specimens as are to be immediately cased up in air-tight cases, nothing further is needed; but as regards such specimens as are left exposed or uncased, ‘a wash of benzoline liberally applied from time to time——say twice a year——to the outside,’ is recommended.

“We have long since proved the efficacy of this fluid, not only in repelling the attacks of moths, and the larvæ of destructive beetles such as _Dermestes lardarius_, but in killing them in skins that have been already attacked by them. We can therefore indorse Mr Browne’s remarks, and may supplement them by a ‘wrinkle’ which he has probably discovered by this time, although he does not refer to it. It is this. If the amateur in search of benzoline applies to the nearest chemist for it, he will be served with the ‘rectified’ fluid, and will be asked three shillings or three and sixpence for an ordinary medicine bottlefull. If he proceeds, however, to an oil and colour shop, and asks for it as supplied for burning in the sponge lamps, he may get a pint for about a tithe of the cost.

“The best way to apply it is to pour some out in a saucer, saturate a pinch of cotton wool with it, and dab it on all over the fur or feathers. The great advantage about it is that, while killing or repelling insects, it does not in the least injure the specimen to which it is applied. We have seen a mounted specimen of a bird almost saturated with it, so that the feathers looked quite draggled; but as soon as the moisture had evaporated, the feathers all resumed their former shape and glossy appearance. Care should be taken not to use it by candle light, as the vapour is inflammable.

“Amongst the seventeen receipts for ‘preservatives’ of different kinds, we do not see a very simple powder which we have used with success for very small bird skins, which were almost too delicate to stand the application of a brush and paste, or soap. It is composed of burnt alum and sugar of lead, and mixed in the proportion of two thirds of the former to one third of the latter. The alum dries, the sugar of lead preserves, and if the specimen while being skinned be dusted with this mixture, it will absorb all moisture as it arises, for which purpose plaster of Paris is usually employed. A very little goes a long way, and it is desirable not to apply too much, lest the astringent nature of the alum should cause the skin to become brittle and crack.

“Possibly Mr Browne has not referred to this mixture on account of the poisonous nature of the sugar of lead. He justly remarks that too much care cannot be exercised in the employment of poisonous preservatives, and we fully agree with him.

“On the subject of his instructions for skinning birds we have not much criticism to offer, except perhaps as regards his mode of filling out the skin after the preservative has been applied, and before the skin is sewn up. We have found by experience that, after the artificial neck of tow or cotton wool has been inserted, and the wing bones tied inside, the skin is much better filled by degrees with little bits of cotton wool inserted piecemeal, instead of with an artificial body ‘as nearly as possible shaped to the original body of the bird.’ The advantage of the former plan is that it is much more quickly executed, and a nice soft skin is the result, instead of a comparatively hard one. By introducing the wool piecemeal, too, scarcely any portion of the skin is left without support on the inside, as is often the case when a ‘made body’ is inserted. This is material; for if there be any want of inside support at a given point, pressure upon that point from the outside will cause the skin to crack. These remarks, however, must be taken to apply only to such specimens as are intended to be preserved as skins, and are not to be set up.

“Few amateurs, probably, give much time to mounting their specimens, for they can get them so well done by professional taxidermists, at prices varying to suit all purses. The art of skinning wild animals and birds, however, and curing or dressing animal hides, should be acquired by every sportsman and naturalist who intends to travel and collect and bring home trophies. To such a one we may specially recommend the chapters which are devoted to this portion of the subject. In this, as in other respects, Mr Browne’s book is a ‘practical’ manual of taxidermy.”

=TAXINE.= A poisonous alkaloid present in the leaves and seeds of the yew (_Taxus faccata_).

=TEA.= _Syn._ THEA, L. The dried leaves of the Chinese tea plants (_Thea Bohea_ and _Thea viridis_).

It was formerly supposed that BLACK TEAS could only be obtained from _T. Bohea_, and GREEN TEAS from _T. viridis_, but Fortune and others have proved that both sorts may be made from either species, and that the differences in colour and flavour depend chiefly on the age of the leaves and the treatment they undergo in the drying process. Another species, named _Thea Assamica_, furnishes ASSAM TEA.

Mulder gives the following as the composition of tea:

Black Green
Tea. Tea.
Essential oil 0·60 0·79
Chlorophyll 1·84 2·22
Wax 0·00 0·28
Resin 3·64 2·22
Gum 7·28 8·56
Tannin 12·88 17·80
Theine 0·46 0·43
Extractive matter 21·36 22·80
Colouring substances 19·19 23·60
Albumen 2·80 3·00
Fibre 28·33 17·80
Ash (mineral substances) 5·24 5·56

Dr Walter Blyth, commenting upon the above, says, the amount of theine is certainly understated.

_Pur._ The chief adulteration of tea which is extensively practised at the present day is mixing it with a certain portion of exhausted tea-leaves, which have been redried and curled. The collection and preparation of these occupy several hundred persons, chiefly women and children, in and about London. The leaves which have been found in the possession of the manufacturers of imitation tea are those of the sloe tree, ash tree, elder bush, and white thorn. According to Mr Warrington, a most extensive system of adulterating tea is practised in China. Many samples directly imported from that country, examined by him, did not contain a single grain of tea, being made up entirely of other leaves. The ordinary green teas he found, for the most part, spurious, being manufactured out of the cheaper black teas. These are ‘faced up’ or ‘painted’ with various colouring substances, powdered porcelain, clay, &c., which are readily perceived under the microscope, and even admit of being separated, and chemically examined.

It is a general practice among the grocers in this country to impart what they call a ‘bloom’ to their green teas by ‘rouncing’ them up with a little calcined magnesia, or finely powdered talc or French chalk. The quantity that adheres to the tea is very trifling, but it, greatly improves its appearance. Black teas are ‘faced,’ in a similar manner, with finely powdered plumbago or black-lead.

Pure China tea is not turned black by being put into water impregnated with sulphuretted hydrogen gas, nor does it tinge a solution of ammonia blue. The infusion is amber-coloured, and is not reddened by the addition of an acid. The ashes left from the combustion of genuine tea are white, and do not exceed 5 to 5-1/2%. If they exceed this they may be chemically examined with the usual tests for alumina, chromate of lead, copper, cyanide of potassium, gypsum, lime, magnesia, &c. Many of these substances may be detected by simply agitating the tea with a little cold water, when they will be detached from its surface, and render the water turbid, or, by their gravity, sink to the bottom.

Mr A. H. Allen[225] arranges the adulteration of tea under four heads, giving at the same time directions for their detection:

[Footnote 225: ‘Chemical News,’ xxix, 123, 167, 189, 221; and xxx, 2.]

1. _Mineral additions for increasing weight or bulk_: (_a_) Magnetic matter. Detected by drawing a magnet under a weighted portion of the tea spread upon paper, whereby the magnetic matter is separated from the tea and may be weighed.

(_b_) Siliceous matter. The ash must be estimated by igniting a weighed portion of the tea. The ash of genuine tea varies from 5·24 to 6·0 per cent. The ash is then boiled with water, the insoluble part again treated with hydrochloric acid, and the silica collected and weighed. Genuine tea does not contain, on an average, more than 0·30 per cent. of ash insoluble in acid; adulterated teas sometimes contain as much as 10 per cent.

2. _Organic adulterations for increasing weight or bulk_: (_a_) Exhausted tea leaves. Best detected by estimating the tannin, gum, soluble ash, insoluble matter, &c.

α. Tannin. 5 gr. of lead acetate are dissolved in 1 litre of water, and the solution filtered after standing; 5 mgms. of pure potassium ferricyanide are dissolved in 5 c.c. of water, and an equal bulk of strong ammonia solution is added. The lead solution is standardised by diluting 10 c.c. to 100 c.c. with boiling water, and adding to it from a burette a solution of 0·1 pure tannin in 100 c.c. of water, until a few drops, when allowed to fall through a filter on to a drop of the ferricyanide solution, spotted on a slab, produce a pink colour. A solution of the tea is made by repeatedly boiling about 2 grams of the finely-powdered sample with 80 c.c. of water, until it is completely exhausted. The solution is filtered and made up to 250 c.c., and used as already described.

The amount of tannin in genuine black tea averages about 10 per cent. A small quantity of tannin, about 2 per cent., remains in the exhausted leaves. The percentage of exhausted leaves, E, in a sample may be estimated, when the per cent. of tannin, T, is known by the equation:

E = (10 - T) / 8 × 100.

β. Insoluble matter is best estimated by boiling the pounded sample repeatedly with water, and drying the residue at 120° C., until the weight is constant. The insoluble matter in black tea varies from 46·7 to 53·6 per cent., while in previously infused leaves it varies between 72 to 75 per cent.

γ Gum. The aqueous decoction is evaporated nearly to dryness, the residue treated with methylated spirit, filtered, washed with spirit, rinsed off the filter with hot water, the liquid evaporated at a steam heat, weighed, ignited, and weighed again. The loss represents gum.

δ. Soluble ash. The aqueous solution of the ash is evaporated, _gently_ ignited, and weighed. Genuine tea contains not less than 3 per cent. of soluble ash, while in exhausted leaves this item falls as low as 0·52 per cent. If S represents the percentage of soluble ash, the percentage of exhausted leaves E may be approximately found in the absence of foreign leaves by the equation:

E = (6 - 2S) × 20.

(_b_) Foreign leaves. The presence of leaves, other than those of the tea plant, may be detected with some accuracy by estimating the insoluble matter, tannin, gum, and ash; but the microscope must decide this question.

3. _Adulterants for imparting a fictitious strength._ (_a_) Extraneous tannin matters, such as catechu, &c., are detected by an unusually high percentage of tannin, as indicated by the lead process. Tea, adulterated with catechu, gives an infusion which quickly becomes muddy on cooling. 1 gram of the sample and 1 gram of pure tea are each infused in 100 c.c. of water, and the solutions poured off from the leaves are precipitated, while boiling, with a slight excess of neutral lead acetate, filtered, and tested as follows:——About 20 c.c. of the pure tea infusion, when gently heated with a few drops of silver nitrate, gives a slight cloudiness only; while tea, containing catechu, gives a copious brownish precipitate, and the liquid acquires a distinct yellow tinge. One drop of ferric chloride gives a light green colour if catechu is present, and a greyish-green precipitate on standing; the solution from pure tea gives a reddish colour with ferric chloride, due to acetate, and no precipitate on standing. These tests are applicable only when catechu is present in tolerably large quantities.

(_b_) Lie tea, when thrown into hot water, falls to powder, because the gum or starch used to keep it in a compact form is dissolved. The liquid may be acidified with sulphuric acid, decolourised with permanganate, and tested for starch. The ash of lie tea is often as high as 30 or 40 per cent.

(_c_) Caper tea is made into little glossy masses by the aid of gum or starch; it is usually much adulterated. The insoluble matter is usually much less than in genuine tea; the gum amounts to 15 or 20 per cent. The soluble ash often falls below 2 per cent.

(_d_) Soluble iron salts are added to give an appearance of strength by the formation of tannate of iron. They are detected by shaking the powdered leaves with cold dilute acetic acid, filtering, and testing for iron, in the filtrate.

(_e_) Alkaline carbonates are sometimes added to tea. The soluble ash gives the yellow sodium flame, if sodium salts have been added; the alkalinity may also be determined in the soluble ash. The average amount of potash (K_{2}O) in tea is about 1·62 per cent.

4. _Facing and colouring materials._ These may be detected under the microscope, or the leaves may be washed with warm water, the colouring matter collected and examined. Indigo is best detected by the microscope; Prussian blue, by boiling with caustic alkali, filtering, and testing for ferrocyanide by ferric chloride. The residue, insoluble in alkali, is fused with alkaline carbonate, evaporated to dryness with hydrochloric acid; the residue tested for silica, and the filtrate tested for lime and magnesia.

Moisture varies from 6 to 8 per cent.

Among domestic substitutes for tea are——the leaves of speedwell, wild germander, black currant, syringa or mock orange, purple-spiked willow herb, winter green, sweetbriar, cherry tree, sloe, &c., all of which are used for tea, either singly or mixed. The addition of a single bud of the black currant to the infusion of ordinary black tea imparts to it a flavour closely resembling that of green tea.

The brownish-coloured powder vended under the name of ‘la veno beno’ is a mixture of 2 parts of tea-dust with 5 parts of powdered catechu or terra japonica. A few grains of this substance thrown into the teapot are described in the advertisements as being capable of more than doubling the strength of the beverage.