Cooley's Cyclopaedia of Practical Receipts Volume Ii Part 258

_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 pota.s.sa 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 pota.s.sa, 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 subst.i.tute 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 285% 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 quant.i.ties or practice to the circ.u.mstances 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 winegla.s.sful 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 quant.i.ty 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 quant.i.ty 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, sc.r.a.ped, 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 b.a.l.l.s, 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 circ.u.mstances 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 a.r.s.enical 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 larvae 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 t.i.the 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 a.s.samica_, furnishes a.s.sAM TEA.

Mulder gives the following as the composition of tea:

Black Green Tea. Tea.

Essential oil 060 079 Chlorophyll 184 222 Wax 000 028 Resin 364 222 Gum 728 856 Tannin 1288 1780 Theine 046 043 Extractive matter 2136 2280 Colouring substances 1919 2360 Alb.u.men 280 300 Fibre 2833 1780 Ash (mineral substances) 524 556

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 quant.i.ty 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 pota.s.sium, 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 x.x.x, 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 524 to 60 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 030 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.

a. Tannin. 5 gr. of lead acetate are dissolved in 1 litre of water, and the solution filtered after standing; 5 mgms. of pure pota.s.sium 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 01 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 quant.i.ty 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.

. 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 467 to 536 per cent., while in previously infused leaves it varies between 72 to 75 per cent.

? 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.

d. 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 052 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.

[Ill.u.s.tration: Leaves and stalks of best tea brought from China (1861) by private hand. Natural size. Generally in commercial tea the leaves are much larger and thicker, and often are cut transversely into two or three parts. Some stalks and remains of flowers are found in all tea, even the best.]