BIXA, in botany, a genus of Polyandria Monogynia class and order. Natural order of Columniferæ; Tiliacæ, Jussieu. Essential character: corolla ten-petalled; calyx fivetoothed; capsule hispid, bivalve. B. ænellana is a shrub with an upright stem, eight or ten feet high, sending out many branches at the top, forming a regular head; these are garnished with heart-shaped leaves ending in a point; the flowers are produced in loose panicles, at the end of the branches, of a pale peach colour, having large petals. There is but one species which is a native both of the East and West Indies.

BLACK, something opake and porous, that imbibes the greatest part of the light that falls on it, reflects little or none, and therefore exhibits no colour. Bodies of a black colour are found more inflammable, because the rays of light falling on them are not reflected outwards, but enter the body and are often reflected and refracted within it, till they are stifled and lost. They are also found lighter, cæteris paribus, than white bodies, being more porous. It may be added, that clothes dyed of this colour wear out faster than those of any other, because their substance is more penetrated and corroded by the vitriol necessary to strike their dye, than other bodies are by the galls and alum which suffice for them. The inflammability of black bodies, and their disposition to acquire heat, beyond those of other colours, are easily evinced. Some appeal to the experiment of a white and black glove worn in the same sun; the consequence will be, a very sensibly greater degree of heat in the one hand than the other. Others allege the phenomena of burning-glasses, by which black bodies are always found to kindle soonest: thus, a burning-glass, too weak to have any visible effect at all upon white paper, will readily kindle the same paper rubbed over with ink.

Dr. Watson, the present Bishop of Landaff, covered the bulb of a thermometer

clothes heat more, and dry sooner in the sun than white clothes. Black is therefore a bad colour for clothes in hot climates; but a fit colour for the linings of ladies' summer hats.

BLACK act, in law, so called from the devastations committed in Hampshire by persons in disguise, or with their faces blacked; to prevent which, it is enacted by 31 George II. c. 42, that persons hunting, armed, and disguised, and killing or stealing deer, or robbing warrens, &c. or setting fire to any house, barn, or wood, or shooting at any person, or sending anonymous letters, or letters signed with a fictitious name, demanding money, &c. or rescuing such offenders; are guilty of felony without benefit of clergy.

BLACK, bone, is made with the bones of oxen, cows, &c. and is used in painting; but is not so much esteemed as ivory-black.

BLACK, currier's, a black made with gallnuts, sour beer, and old iron, termed the first black. The second black, which gives the gloss of the leather, is composed of gallnuts, copperas, and gum arabic.

BLACK, earth, a sort of coals found in the ground, which the painters and limners use to paint in fresco, after it has been well ground.

There is also a black made with gall-nuts, copperas, or vitriol, such as common ink. And a black made with silver and lead, which serves to fill up the cavities of engraved things.

BLACK, ivory, otherwise called velvetblack, is burnt ivory, which becoming quite black, and being reduced to thin plates, is ground in water, and made into troches, to be used by painters, and by jewellers, who set precious stones to blacken the ground of the collets, and give the diamonds a teint or foil. In order to be good, it ought to be tender, friable, and thoroughly ground.

BLACK, lamp, the sooty smoke of rosin. There is some in powder and some in lumps, and is mostly brought from Sweden and Norway. It is used on various occasions, particularly for making the printers' ink, for which purpose it is mixed with oil of walnuts, or linseed, and turpentine, all boiled together.

BLACK lead has long been known under the name of plumbago, it is however properly denominated in the modern chemistry according to its component parts, a car

to be bored with an augre to a proper depth, and a charge of gunpowder introduced. The screw is to be turned into the hole till it nearly touches the powder; a quick match is then to be put down the touchhole till it reaches the charge. The quick match is eighteen inches long, to afford the operator an opportunity of retiring, after lighting it, to a place of safety: it is made by steeping a roll of twine or linen thread in a solution of saltpetre.

BLATTA, the cock-roach, in natural history, a genus of insects of the order Hemiptera. The generic characters are, head inflected; antennæ setaceous; wings flat, subcoriaceous; thorax flattish, orbicular, margined; feet formed for running; hornlets two over the tail. The insects of this genus, and their larvæ wander about by night, and secret themselves by day. They are fond of warmth, and haunt houses, devouring meal, and whatever provisions they can get at: they run with great celerity, and are destroyed by the fumes of charcoal. In hot climates they are a great pest to society, by not only devouring whatever they can get at, but some of the species leave a very unpleasant smell, which is apt to remain a considerable time on the articles which they have passed over. The largest of the genus is, as its name imports, the B. gigantea, a native of many of the warmer parts of Asia, Africa, and South America, of which the following account is given by Drury in his "Exotic Insects." "The cock-roach," says he, "are a race of pestiferous beings, equally noisome and mischievous to natives and strangers, but particularly to collectors. These nasty and voracious insects fly out in the evenings and commit monstrous depredations: they plunder and erode all kinds of victuals, drest and undrest, and damage all sorts of clothing, especially those which are touched with powder, pomatum, and similar substances; every thing made of leather, books, paper, and various other articles, which, if they do not destroy, at least they soil, as they frequently deposit a drop of their excrement where they settle, and some way or other by that means damage what they cannot devour. They fly into the flame of candles, and sometimes into the dishes; are very fond of ink and oil, into which they are apt to fall and perish. In this case they turn most offensively putrid, so that a man might as well set over the cadaverous body of a large animal, as write with the ink in which they have died. They often fly into

persons' faces or bosoms, and their legs being armed with sharp spines, the pricking excites a sudden horror not easily described. In old houses they swarm by myriads, making every part filthy beyond description wherever they harbour, which in the day-time is in dark corners, behind all sorts of clothes, in trunks, boxes, and in short every place where they can lie concealed. In old timber and deal houses, when the family is retired at night to sleep, this insect, among other disagreeable properties, has the power of making a noise which very much resembles a pretty smart knocking with the knuckle upon the wainscotting. The B. gigantea, in the West Indies, is therefore frequently known by the name of the drummer. Three or four of these noisy creatures will sometimes be impelled to answer one another, and cause such a drumming noise, that none but those who are very good sleepers can rest for them. What is most disagreeable, those who have not gause curtains are sometimes attacked by them in their sleep: the sick and the dying have their extremities attacked, and the ends of the toes and fingers of the dead are frequently stripped, both of the skin and flesh. This insect is not at present known in Europe, though many of the other species, of which Gmelin enumerates 47, have been introduced by ships from the warmer regions, and are become nuisances in our houses. It has been supposed that the gigantea has been seen once at least in our own country, concerning which Mouffet writes: "I have heard from people worthy of credit, that one of the blatte was found on the roof of Peterborough church, which was six times larger than the common blatta, and which not only pierced the skin of those who endeavoured to seize it, but bit so deep as to draw blood very copiously it was as large as one's thumb, and being confined in the cavity of the wall, after two or three days it made its escape, unnoticed by any one." In Asia this species is as large as a good sized hen's egg. B. orientalis, or common black cockroach, was found in America, but has long been naturalized in Europe: female with mere rudiments of wing-cases and wings: egg subcylindrical with a crenate ridge, and half as large as the abdomen. This is frequently met with in London and elsewhere under the name of black beetle. B. americana is native of America, and has of late years appeared in Europe, having been brought over in raw sugar. B. irrorata is

nearly as large as B. gigantea, and is a native of New Holland; head pale; front subferuginous; the hind margin brown; wing-cases with an abbreviated black line at the base.

BLAZONING, or BLAZONRY, in heraldry, the art of decyphering the arms of noble families. The word originally signified the blowing or winding of a horn, and was introduced into heraldry as a term denoting the description of things borne in arms, with their proper significations and intendments, from an ancient custom, the heralds, who were judges, had of winding an horn at justs and tournaments, when they explained and recorded the achievements of knights.

In blazoning a coat of arms, you must always begin with the field, and next proceed to the charge; and if there be many things borne in the field, you must first name that which is immediately lying upon the field. Your expressions must be very short and expressive, without any expletives, needless repetitions, or particles. Such terms for the colours must be used as are agreeable to the station and quality of the bearer. All persons beneath the degree of a noble must have their coats blazoned by colours and metals; noblemen by precious stones, and kings and princes by planets.

BLEACHING, in the arts, is a process that consists of a series of operations, partly chemical and partly mechanical, to which vegetable and animal fibres are subjected for the purpose of discharging their natural colour, and thus rendering them white, either before or after they have been manufactured. Now as almost all the articles of clothing are formed of vegetable or animal fibres, and as these are for the most part required to be made as white as possible, either to be worn in this state, or as preparatory to being dyed or printed, it is obvious that the art of bleaching is one of great importance. The substances upon which the bleacher is required to exercise his art are cotton, flax, hemp, wool, and silk. The three former being of vegetable origin require a somewhat similar treatment, which in many particulars differs from that which is applicable to the two latter.

The art of bleaching consists, not merely in discharging the colour of the thread, but likewise in removing the colouring matter itself, as otherwise a sensible shade would be regained. In the old method this was attained by alternate exposure of the thread VOL. I.

or cloth to the action of light, humidity, and atmospheric air, and to an alkaline ley, the cloth being macerated in a solution of potash, exposed on the field, to the air and sun, and frequently sprinkled with water; and these alternate practices being continued until the bleaching was complete. In the new method, the action of the oxymu riatic acid is substituted for that of the light, air, and water; and it answers the same purpose by affording oxygen to the colouring matter, thus impairing the colour, and probably rendering the matter soluble in the alkaline solution.

At first this process was performed by exposing the cloth to the action of the pure acid in the state of gas. It was found, however, to act unequally on the cloth, the texture being injured in one part, while in another it was imperfectly whitened. The solution of it therefore in water was substituted, and even this requires to be considerably diluted. The bleaching liquor, according to the directions given by Berthollet, is prepared by putting six parts of black oxide of manganese and sixteen of muriate of soda into a glass, or earthen retort, or a leaden bottle, and pouring upon them twelve parts of sulphuric acid, diluted with nine of water. The retort, or bottle is connected by a tube with a receiver, designed to retain any common muriatic acid that may pass over; from this vessel another tube issues, which is inserted in a large wooden cask filled with water. The tube descends nearly to the bottom of the cask, so that the gas has to rise through the whole body of the water at the same time, the absorption of it is promoted by the motion of a circular frame placed in the middle of the cask, and which can be turned round at the top. The oxygenated acid is thus easily condensed. After the first disengagement of the gas has ceased, heat is applied to the retort by placing it in a sand bath, or if a leaden bottle be used, by placing it in a vessel of boiling water. So much water is used that the oxygenated acid is very weak; it requires to be stronger for coarse than fine cloth, and for linen than for cotton; the average quantity stated by Berthollet is 100 quarts for every pound of muriate of soda that has been used. cloth to be bleached is prepared by macerating it in warm water for some hours, to take up what part of the colouring matter may be soluble. It is then boiled in an alkaline ley, prepared from 20 parts of water, and one part of the potash of com Na

The

merce rendered more active by having been mixed with one third of lime. After sufficient boiling it is washed with water, and put into close wooden troughs, containing the oxygenated acid, in which it is allowed to macerate for 3 or 4 hours, pressing the cloth frequently, and exposing its surfaces to the action of the liquor. It is thus alternately exposed to the action of the alkaline ley and the oxygenated acid, till its colouring matter is completely extracted, or it is sufficiently bleached, which requires in general from 4 to 8 immersions, according to the nature and coarseness of the cloth, cottou requiring fewer immersions in the bleaching liquor than linen. The subsequent steps of the process are to rub the cloth strongly with soft soap in warm water. This renders the surface more smooth aud uniform, and takes away the smell of the oxygenated acid, which otherwise remains a considerable time. The cloth is again washed, and is lastly immersed for a short time in water, in which, from a one-sixtieth to a one-hundreth part of sulphuric acid has been dissolved. The cloth thus acquires a much finer whiteness, from the sulphuric acid dissolving the remaining colouring matter which has resisted the action of the alkali and oxygenated acid, as well as a small. quantity of iron and calcareous earth contained in all vegetable matter, or even deposited in the cloth from the alkaline leys. Lastly, the cloth is generally exposed to the air for some days, and watered, to carry off any remains of either of the acids, and to remove completely the odour of the oxygenated acid. The theory of the action of the oxygenated muriatic acid in bleaching is very simple, as stated by Berthollet. Its analogy to the common process by exposure to the air and light, he observes, is complete. The end obtained by either is the combination of oxygen with the colouring matter of the vegetable. By this combination the colour is nearly destroyed, and the matter on which it de. pends is at the same time rendered soluble in the alkaline solution. Hence the necessity of the alternate application of these two chemical agents; the one removing from the cloth what the other has rendered soluble, and which, although whitened, would regain part at least of its colour in time. Hence it is found, that the oxygenated muriatic acid is in this operation converted into common muriatic acid, and the alkaline solution is at length so loaded

with colouring matter, that it becomes unfit to be used. The only difference between the two methods is, that in the one the oxygen is presented in a much more concentrated state than in the other, which facilitates the process, or renders it more rapid without injuring the strength of the fibre. At least, the only injury of this kind that can happen must arise from improper management; having used too strong an acid, or the not washing the cloth sufficiently after the process is finished. The greatest difficulty attending the use of oxymuriatic acid arose from its suffocating odour, which rendered it almost impossible to work with it in an open vessel, and any apparatus contrived to turn the cloth and expose fresh surfaces of it to the action of the liquid in close vessels has been found imperfect. The addition of an alkali to the liquid removes in a great measure the odour of the acid, or at least prevents its unpleasant effects; and although it at the same time diminishes to a certain extent its bleaching power, this is more than compensated for by the advantage. The quantity of alkali added amounts to about 1lb. of the potash or pearlash of commerce to the quantity of acid prepared from 4lbs. of muriate of soda. And to avoid the effervescence which would arise from the disengagement of the carbonic acid, during the combination of the oxymuriatic acid, the potash is deprived of it by the previous addition of lime, the alkaline solution after its operation being poured off clear.

Independently of the weakening of the power of the acid, by this addition, a considerable expense was introduced by the use of the alkali; and it became an object of importance to the manufacturers of this country to substitute a cheaper substance which should have the same effect. Lime. was tried at first in an imperfect manner, but at length with such improvements that it is now always used. The difficulty of using it arose from the insolubility of the lime in water, the quantity taken up being so inconsiderable, that the solution could have little effect in correcting the odour of the acid. A very important improvement, therefore, was that of using lime suspended in water, and kept in suspension by an agitation in a close vessel, into which the gas was transmitted. Its condensation was thus facilitated, and the compound which is formed with the lime being soluble in water, the undissolved or unsaturated lime was

allowed to subside, and the clear liquor was fit for the purpose of bleaching.

An improvement, however, of still more importance has been made by Mr. Tennant of Glasgow, and a patent obtained for it; viz. that of combining the oxymuriatic acid with dry lime, and dissolving a certain proportion of this compound in water to form a bleaching liquor. It perhaps could scarcely have been supposed that such a combination could have been formed, so as to retain the powers of the acid. But the trial has fully succeeded, and the advantages derived from it are important; the compound can be carried easily to a distance, and the manufacturer need not prepare it himself, which is always an advantage, especially where he does not work on a large scale. The combination is formed by introducing the oxymuriatic acid gas through leaden tubes into slaked lime, prepared from chalk, by which it is absorbed. Solutions of this are prepared of different strengths, according to the purposes to which they are to be applied, the strength being judged of by the hydrometer, and by the quantity requisite to destroy the colour of a diluted solution of indigo in sulphuric acid. The process of bleaching, as now performed by these liquors, differs little from that which has been already described as executed by the solution of the oxymuriatic acid alone in water. To these methods, however, is to be added the more recent discovery of bleaching by an alkali, assisted by watery vapour and a high temperature, and which, either alone or combined to a certain extent with the method by the oxymuriatic acid, is now practised with so much advantage. In this method, which has been long in use in some of the eastern countries, and of which notice was first given by Chaptal, the cloth or thread is impregnated with a solution of potash or soda, rendered active by the carbonic acid having been entirely abstracted from the alkali by lime; it is suspended loosely, and, with an extensive surface, in a close boiler, a quantity of the same solution being in the bottom, and heat is applied, the boiler being closed, with a safety valve in the cover, so that the vapour under pressure may receive a high temperature. It is kept in this situation for a number of hours. The thread or cloth when cold is washed, and either exposed on the field, or subjected to the action of the oxymuriatic acid in some of the forms under which it has been used. It is thus at once rendered perfectly white. The superiority of this

method probably arises from the high temperature, and the solvent power of the wa tery vapour, favouring the action of the alkali on the colouring matter, while this vapour penetrates the fibres of the cloth so effectually, that the matter is in a great measure dissolved and removed.

The animal fibres that are subjected to the bleaching process are wool and silk. These cannot be treated in the same manner as vegetable substances: a strong alkaline ley will dissolve them, and oxymuriatic acid will both weaken them and turn them yellow. The colour of manufactured wool resides partly in its own oil, and partly in the greasy and mucilaginous applications which it receives in being prepared for the loom. Both the one and the other are easily got rid of, by the action of fuller's earth and soap in the process of fulling. Fuller's earth is a very fine-grained absorbent earth, which by itself is capable of mixing rather than combining with vegetable or animal oils, and rendering them miscible with water: its action is found, however, to be increased by the addition of soap; and woollen cloth being beat in a fulling-mill with hot water, and a proper mixture of earth and soap, or of soap alone, and afterwards well washed and dried in the air, receives all the bleaching which it requires, or is indeed capable of. It is then of a white colour, somewhat verging towards yellow: this last tinge may be made to disappear by the addition of a very small quantity of stone blue in the water in which the cloth is last washed, or by exposing it to the fumes of burning sulphur. By this latter method, however, it acquires a certain harshness of feel, and is apt to turn very yellow when washed with soap. Both the colour and harshness of raw silk depend entirely on a yellow varnish with which it is naturally covered. This varnish may be in part removed bý long boiling in simple water. It is considerably more soluble in alcohol; but the most effectual and expeditious way of clearing is by putting it in a linen bag, and boiling it for some hours in a solution of white soap in water, then rincing it in clean water, and repeating the process till it is quite white, and exhibits the peculiar lustre of this beautiful substance. Some of the French chemists have endeavoured to lessen the consumption of soap, by proposing various substitutes; but nothing is so effectual and expeditious as the purest white soap, and the article itself is so valuable, as amply to repay this expense.