Cooley's Cyclopaedia of Practical Receipts Volume Ii Part 255

"This mixture of stearic acid and wax or spermaceti is very suitable for forming the exterior coating of the candle; it is transparent, and of perfect whiteness, and, as it is devoid of oxalic acid, it does not injure the moulds; whilst at the same time, as it is less fusible than pure stearic acid, candles made with it do not run. The first coating may be run hot without crystallising; the interior of the candle, being protected from without against too sudden a cooling, may also be run somewhat hot; by this means the candle acquires a whiteness and a transparency which cannot be realised by other processes." ('Le Moniteur Industriel.')

The sulphuric acid saponification of inferior tallow and other solid or semi-solid fatty bodies is now carried out on a very large scale for producing the cheaper varieties of 'stearine candles.' For this purpose, the tallow or fat is mixed with 5 or 6% of concentrated sulphuric acid, and exposed to a steam heat of 350 to 360 Fahr. After cooling, the black ma.s.s thus obtained crystallises to a tolerably solid fat, which is well washed once or twice with water, or high-pressure steam, and is then submitted to distillation by the aid of steam heated to about 560 Fahr.

The product of the distillation is beautifully white, and may be at once used for making candles. It is better, however, to first submit it to the processes of cold and hot pressing, whereby a much more solid fat is obtained.

According to M. Pohl, palm oil or palm tallow is most easily purified by simple exposure to a high temperature, provided it has been first well defecated. When quickly heated to about 465 Fahr., and kept at that temperature for from 5 to 15 minutes, it is completely decoloured. The product has a slight empyreumatic odour, but this disappears by age, exposure, or saponification, and the natural violet odour of the oil returns. Cast-iron pans should be employed in the process, and should be only 2-3rds filled, and well covered during the operation.

By the distillation of sulphurated palm oil in closed vessels, at a heat ranging from 570 to 600 Fahr., from 68% to 75% of a mixture of palmitic and palm-oleic acid pa.s.ses over, of which 25% to 30% is colourless, hard, and crystalline, and the rest darker and softer. (Pohl.) The residuum in the still is a fine hard pitch. See CANDLES, FAT, GLYCERIN, OILS (Fixed), STEARIC ACID, &c.

=TAMAR'A.= A mixed spice used in Italian cookery, consisting of cinnamon, cloves, and corianders, of each 2 parts; aniseed and fennel seed, of each 1 part.

=TAM'ARIND.= _Syn._ TAMARINDUS (B. P., Ph. L., E., & D.), L. The pulp or preserved fruit or pod of the _Tamarindus Indica_, or tamarind tree.

Tamarind pulp is refrigerant and gently laxative. Mixed with water, it forms a grateful acidulous drink in fevers.--_Dose_, 1/4 oz. and upwards.

_Composition of the Tamarind._--Vanquelin.

Citric acid 940 per cent.

Tartaric " 155 "

Malic " 045 "

Bitartrate of potash 325 "

Sugar 1250 "

Besides gum, vegetable jelly, parenchyma, and water.

=TANKS.= The difference between water-tanks and cisterns is not very obvious. Perhaps the definition the most nearly representing the general idea respecting them would be, that whilst both were receptacles for water, in tanks water would be stored for a longer period than in cisterns, which supplying the constantly recurring needs of a house or a building of any kind would be more frequently filled and emptied; although in many instances there might be no such distinction between them, and they might be regarded as synonymous. In whatever sense the terms may be understood, the remarks that follow as to their construction and management have a common application.

The materials for tanks and cisterns for the reception of water consist of stone, cement, brick, slate, iron, zinc, and lead. Of these materials, the best, although the dearest, is slate. The slate cistern, however, is occasionally liable to leakage, a defect mostly arising from the employment of mortar instead of cement for joining the slabs.

Wrought-iron cisterns and tanks as well as the pipes in connection with them are in very general use. The tendency of both to corrosion by the action of the water is considerably reduced by coating the insides with Portland cement or a vitreous glaze.

Mr Burn advocates the employment of a compound of tar, which, he says, most effectually protects them. Zinc, although cheap, and little acted upon by water, is seldom employed for cisterns. Dr Osborne says he has seen several cases of zinc poisoning, caused by drinking water that had pa.s.sed through zinc pipes, or had stood in zinc pails. Equal, if not greater risk is incurred when drinking-water is kept in lead cisterns, or is made to run through lead pipes. In setting up cisterns or tanks made of stone or cement, common mortar must not be used, as lime is taken up and the water is rendered hard in consequence.

In seasons of drought it is by no means an unusual occurrence for many rural districts to lack a sufficiency of water, the limited supply of which entails considerable suffering, sometimes terminating fatally upon farm stock, with frequent loss to the owners. Few persons, perhaps, can form a correct idea of the immense quant.i.ty of water that in the shape of rain falls even in the least humid portions of our islands. If this rain, which is now allowed to run waste, were properly collected and stored, it would form a valuable resource in times and at places where there was a dearth or scarcity of this necessary element.

Mr Bayley Denton, writing on this subject, says:--"Take an ordinary middle-cla.s.s house in a village with stabling and outbuildings, the s.p.a.ce of ground covered by the roofs will frequently reach 10 poles, while the s.p.a.ce covered by a farm-labourer's cottage and outbuildings will be 2-1/2 poles.

a.s.suming that the roof is slate and the water dripping from it is properly caught by eave-troughing, and conducted by down-pipes and impervious drain-pipes into a water-tight tank sufficiently capacious to prevent overflow under any circ.u.mstances, and that by this method 20 inches of water from rain and dew are collected in the course of the year, the private houses will have the command of 28,280 gallons, and the cottage 7070 gallons in a year.... A tank 16 feet long, and ten feet wide, will hold 1000 gallons in every foot of depth, and where the water is not wanted for drinking, it need not be covered, except with a common boarded floating roof of half-inch boards fastened together. This floating roof keeps the water clean, and prevents evaporation."[222]

[Footnote 222: 'On the Storage of Water,' by Bayley Denton.]

Leakage of pipes of any kind into a cistern or tank should be particularly guarded against. Another important precaution claiming adoption is to see that the overflow-pipe is not directly connected with the sewer, for if it be, the sewer gases will rise through it, and being prevented escaping from the cistern because of its covering, will become absorbed by the water. To obviate this, the overflow-pipe is curved, so as to force a syphon trap; but this device conduces to a sense of false security, since it mostly fails owing to the evaporation of the water in it, or to the gases forcing their way through it. The overflow-pipe, therefore, should never have direct communication with the sewer, but should always end above ground, and discharge over a trapped grating into it. For similar reasons the same tanks or cisterns should never supply the water used for culinary or drinking purposes and also the water-closets.

To the water in the tanks attached to these latter, some disinfectant substance should from time to time be added; more particularly during hot weather.

Unless a cistern be efficiently protected, particularly if it be placed in an exposed situation, various disgusting and filthy substances, such as the ordure of birds, cats, rats, and dead insects, &c., will be liable to fall into it, and foul its contents. This must not only be guarded against by the proper means, but even where the contamination may not be suspected, or likely to occur, the cistern should be frequently examined and periodically cleansed; part of the proper carrying out of which should consist in always running off the water remaining in it and renewing it with fresh.

The London and General Water Purifying Company have adopted an excellent idea in connection with tanks and cisterns; they fit them with filters, so that the water drawn from the pipes shall have been submitted to filtration previous to delivery.

=TAN'NATE.= A salt of tannic acid.

=TAN'NER'S BARK.= The best of this is oak bark; but the bark of the chestnut, willow, and larch, and other trees which abound in tannin, are also used for preparing leather.

=TAN'NIC ACID.= C_{27}H_{22}O_{17}. _Syn._ TAN, TANNIN, GALLO-TANNIC ACID; TANNINUM, ACIDUM TANNIc.u.m (B. P., Ph. L., D., & U. S.), L. A peculiar vegetable principle, remarkable for its astringency and its power of converting the skins of animals into leather.

_Prep._ 1. (Pelouze.) From galls, in moderately fine powder, by percolation, in a closed vessel, with sulphuric ether that has been previously agitated with water. After some time the percolated liquid will be found divided into two distinct portions, the lower and heavier one being a watery solution of tannic acid, and the upper one an ethereal solution of gallic acid and colouring matter. Fresh ether must be pa.s.sed through the powder as long as the lower stratum of liquid continues to augment. The two fluids are now carefully separated, and after the heavier one has been well washed with ether, it is gently evaporated to dryness, preferably under the receiver of an air pump, or over sulphuric acid. The ether may be recovered unaltered from the ethereal solution, by cautious distillation in a retort connected with a Liebig's condenser supplied with ice-cold water. _Prod._ About 40%.

2. (Ph. D.) From galls, in tolerably fine powder, 8 oz., and a mixture of sulphuric ether, 3 pints, with water, 5 fl. oz.; by percolation, in successive portions, like the last; the aqueous solution of tannic acid being evaporated, and finally dried at a heat not exceeding 212 Fahr.

_Prop., &c._ Pure tannic acid is perfectly white, but as ordinarily met with it has a slight yellowish colour, owing to the action of the air; it is uncrystallisable; possesses a powerful and purely astringent taste, without bitterness; is freely soluble in water, less so in alcohol, and only very slightly in ether; it reddens vegetable blues; when boiled with acids, it a.s.similates water and splits into gallic acid and grape sugar; when heated in the dry state, it suffers decomposition, metagallic and pyrogallic acids being formed; it unites with the bases, forming salts called tannates, which are characterised by striking a deep black with the persalts of iron (ink), and forming a white precipitate with gelatin.

E. Schmidt[223] gives the following comparative method of determining tanning materials, stating, preliminarily, "that the question to be solved is, knowing that a certain weight of pure tannin is required to obtain a certain result, how much of another tanning body, _e.g._ the extract of a wood, is required to produce the same result? None of the published methods for the determination of tannin is sufficiently precise, easy, and rapid for industrial purposes."

[Footnote 223: Chem. News, from 'Bull. de la Soc. Chem. de Paris.']

The author proposes a modification of Pibram's method with sugar of lead, the modification being as follows:

A. _Preparation of the Test Liquor._ Fifty grams neutral acetate of lead are dissolved in 400 grams of alcohol, of 92 per cent., and distilled water is added to make up 1 litre.

On the other hand, 1 gram of tannin is dissolved in 40 grams of alcohol of the same strength, and the solution is made up with water to the bulk of 100 c.c. This being done, 10 c.c. of the tannin solution are mixed with 20 c.c. of water, and heated to 60. The lead liquor is then run into the hot solution from a burette, graduated to tenths of a c.c., so long as a precipitate is formed. At this temperature, and with these alcoholised liquids, the precipitate forms and settles rapidly. Iodide of pota.s.sium may be used as an indicator to show excess of lead, proceeding in the same manner as is done with ferrocyanide in t.i.trating phosphates with nitrate of uranium. If we suppose that to precipitate 10 c.c. of the tannin solution 28 of the lead liquor have been required, then 28 c.c. of the latter = 010 gram of tannin.

B. _Preparation of the Sample to be tested._ Suppose that chestnut bark is to be examined. It is coa.r.s.ely powdered, and 10 grams are mixed with an equal volume of washed sand, and exhausted with water at 50 or 60 C. The filtered liquid is evaporated to dryness in a water bath in a tarred porcelain capsule. After evaporation the capsule is weighed, which shows the yield of the bark in aqueous extract. This is taken up in 40 grams of alcohol at 92, and water is added to make up 100 c.c. The liquid is filtered if needful. In this manner the resinous, alb.u.minoid, pectic, and gummy matters are got rid of.

C. _t.i.tration._ The liquid thus prepared is divided into two parts. The first, one third of the entire volume, serves for direct determination of the acetate of lead. Suppose that a gram of the dry extract of chestnut has required, for 10 c.c. of the tannin liquor, in three successive experiments, 16, 17, and 16 of the burette, which corresponds to 57 per cent. of tannin. Thus figure 57 represents not only tannin, but every other substance capable of precipitating acetate of lead.

The tannin is then absorbed with bone black, previously washed with hydrochloric acid, and dried at 100 C. in the following manner:--We act with bone black upon the tannin liquor, and on a solution of pure tannic, prepared at a standard somewhat lower than that indicated for the extract by the first direct t.i.tration. In the present case this solution of tannin should be prepared at 55 per cent.

From one and the same gla.s.s tube, about 1 centimetre in diameter, we cut off two lengths of 20 centimetres each, and we draw out each at one of its ends. The two tubes are fixed perpendicularly with the points downwards, and plugged with a little carded cotton. Into each is put 10 grams of the bone black, pouring into one of them the second part of the tannin liquor under examination, and into the other the same volume of the pure solution of pure tannin at 55 per cent.

Twenty c.c. of the tannin liquor (which will be found to have retained its original brown colour in spite of the bone black) are now heated to 60 C., and the standard lead liquor is added from the burette as before.

Two successive trials show 16 = 8 for 10 c.c. in place of the 16 found for 10 c.c. on direct t.i.tration. On the other hand, 20 c.c. of the solution of pure tannin require 14, or 7 for 10 c.c. Thus we see that in the tannin liquor (chestnut extract) there is a certain quant.i.ty of matter which acts upon the standard lead solution like tannin, corresponding to 1 of the lead liquor, _i. e._ to 357 thousandths of a centigram of tannin; 28, therefore, correspond to 10 centigrams. The figure 57, obtained by direct t.i.tration, is, therefore, too high by 357 per cent., and the extract contains 57 - 357 = 5343 per cent. of tannin.

_Uses, &c._ The value of substances containing tannin in the preparation of leather is well known. In its pure form it is used as an astringent in medicine; internally, in diarrha, haemorrhages, as a tonic in dyspepsia, &c.; externally, made into a gargle, injection, or ointment.--_Dose_, 1 to 10 gr., in the form of pills or solution. See GALLIC ACID, &c.

=TAN'NIN.= See TANNIC ACID.

=TAN'NING.= When the skin of an animal, carefully deprived of hair, fat, and other impurities, is immersed in a dilute solution of tannic acid, the gelatin gradually combines with that substance as it penetrates inwards, forming a perfectly insoluble compound, which resists putrefaction completely; this is tanned leather. In practice, lime water is used for cleansing and preparing the skin, water acidulated with oil of vitriol for 'raising' or opening the pores, and an infusion of oak bark, or sometimes of catechu, or other astringent matter, as the source of tannic acid. The process itself is necessarily a slow one, as dilute solutions only can be safely used. Skins intended for the curriers, to be dressed for 'uppers,'

commonly require about 3 weeks; and 'thick hides,' from 12 to 18 months.

Of late years various ingenious contrivances have been adopted, with more or less success, to hasten the process of tanning skins and hides. Among these may be mentioned the employment of stronger tan solutions, the application of a gentle heat, puncturing the skins to afford more ready access for the liquid to their interior parts, and maceration in the tan liquor under pressure, either at once or after the vessel containing them has been exhausted of air by means of an air-pump. On the merit of these several methods it has been remarked "that the saturated infusions of astringent barks contain much less extractive matter, in proportion to their tannin, than the weak infusions; and when the skins are quickly tanned in the former, common experience shows that it produces leather which is less durable than leather slowly formed." (Sir H. Davy.) "100 lbs. of skin, quickly tanned in a strong infusion of bark, produce 137 lbs. of leather; while 100 lbs., slowly tanned in a weak infusion, produce only 117-1/2 lbs." "Leather thus highly (and hastily) charged with tannin is, moreover, so spongy as to allow moisture to pa.s.s readily through its pores, to the great discomfort and danger of persons wearing shoes made of it." (Ure.)

According to Mr G. Lee, much of the original gelatin of the skin is wasted in the preliminary processes to which they are subjected, more especially the 'liming' and 'bating,' He says, that 100 lbs. of perfectly dry hide, cleaned from extraneous matter, should, on chemical principles, afford at least 180 lbs. of leather.

MOROCCO LEATHER is prepared from goat or sheep skins, which, after the action of lime water and a dung bath, are slightly tanned in a bath of sumach. They are subsequently grained, polished, &c.

RUSSIA LEATHER is generally tanned with a decoction of willow bark, after which it is dyed, and curried with the empyreumatic oil of the birch tree.

It is the last substance which imparts to this leather its peculiar odour and power of resisting mould and damp. See LEATHER, TANNIC ACID, TAWING, &c.

=TANTALIC ACID.= _Syn._ TANTALIC ANHYDRIDE; COLUMBIC ACID. Rose believed this substance to be a dioxide, to which he gave the formula TaO_{2}; but the subsequent researches of Marignac, and the crystalline form of pota.s.sic tantalic fluoride 2KF, TaF_{5}, seem to show that it is to be regarded rather as Ta_{2}O_{5}.