malisation, if by it be meant impregnating the cloth with an animal matter, and by the power of the microscope, or any better method, look for the whole truth from some other source than chemical analysis. I am at present inclined to believe that it is a mechanical operation united to a chemical, and that the frequent immersions in the imperfect soap are equivalent to laying on the first, second, third, &c., coats, preparatory to finishing a fine painting in oil. A very eminent calico inanufacturer, whom I consulted on the Turkey-red process, assured me that the only essential mordants are oil and alumina; and that bright and fast reds, equal to any produced by the usual complicated process with sheep's dung, galls, and blood, may be obtained without these articles.

OF DYEING SCARLET.

184. Scarlet may be regarded as one of the compound colors arising from a mixture of the red and yellow coloring matters. Scarlet is the finest and most splendid of all the colors, and the great demand for, it has excited several chemists of distinction to improve and facilitate the process of producing it. We shall here briefly notice the old method of dyeing scarlet, which is still practised by some dyers, both in this country and on the continent, and then give the improved method proposed by Dr. Bancroft in his excellent treatise already mentioned.

185. We cannot, says M. Berthollet, expect to obtain the desired shade from the doses prescribed in the processes, from variations in the quantity of the coloring particles contained in the different kinds of fine cochineal, and particularly from the solutions of tin that are used differing considerably from each other; but the just proportions of the ingredients to be employed may be readily determined by trials in the small way, so as to obtain the shade called for; and, if the pieces which are dyed be above or below this shade, it is not difficult to find the suitable proportions.

186. In the process of dyeing scarlet two operations are observed, viz. the boiling, and the reddening. The first or boiling operation is thus conducted:-For 100 pounds of cloth, a quantity of soft water is heated in a tinned boiler, till it be rather more than lukewarm, after which six pounds of cream-of-tartar are dissolved in it. When the water is a little warmer, half a pound of finely powdered cochineal is added and well mixed with the solution of tartar. Immediately after, five pounds of very clear solution of tin are poured in, and carefully mixed. When the bath begins to boil, the cloth is put in, and rapidly turned two or three times with the winch, then more slowly, and is left to boil for two hours, after which it is taken out, drained, exposed to the air, and washed in the running stream. 187. In preparing for the second bath the boiler must be emptied, filled again with fresh water, and, when this is near the boiling heat, five pounds and three quarters of powdered cochineal are put in and carefully mixed, and when, on ceasing to stir the liquor, a crust forms on the surface, and begins to break, thirteen or fourteen pounds of solution of tin are poured in.

Sometimes, after this, the liquor begins to ris? above the brim of the boiler, which must be prevented by putting in some cold water. When the solution is well mixed in the bath, the cloth is immersed, taking care to turn the winch_rapidly for the first two or three turns. It is then to be boiled for about an hour, pressing it down as often as it rises to the surface. After this it is taken out, exposed to the air to cool, washed in the stream, and dried.

188. On examining the proportions of cochineal and of solution of tin, used either in the boiling, or in the reddening, it appears that they are by no means fixed. There are some dyers, who, according to Hellot's account, succeed very well by putting two-thirds of the composition, and a fourth of the cochineal, into the boiling, and the remaining third of the composition, with the remaining three-fourths of the cochineal, into the reddening. He also asserts that it does no harm to use tartar in the reddening, provided not more of it than half the weight of the cochineal be put in; and he thinks, that it even renders the color more permanent. Some dyers do not take the cloth out of the boiling, but simply refresh it to make the reddening in the same bath, by pouring in an infusion of cochineal, which they have made apart, and with which they have mixed the proper quantity of composition. In this way they save time and fuel: and they affirm that the scarlet is equally fine.

189. Different authors recommend different proportions of the materials used in the boiling process. Scheffer prescribes one part of solution of tin for ten parts by weight of cloth, with an equal quantity of starch and of tartar as of solution. He remarks, that the starch tends to make the color more uniform, and he recommends to throw into the water, when it boils,

of cochineal; to agitate well; to let the wool boil in it for an hour, and then to wash it. He prescribes next, the boiling for half an hour in the bath, which serves for the reddening, with

of starch, of solution of tin, of tartar, and of cochineal.

It appears, that Scheffer employs a much smaller quantity of solution of tin than Hellot; but what he does employ contains much more tin.

190. Poerner describes three principal processes, according as the shade is to be more or less deep, or more or less of an orange hue, which he wishes to give to the scarlet. He varies the proportions of the solution of tin, of cochineal, and tartar, or omits the last ingredient.

For conducting the process of the scarlet dye in the most beneficial manner, and for varying its results, according to the end in view, the effect of each of the ingredients employed in it must be ascertained. We need not however proceed with a detail of processes which have been superseded by others that are from experience found to be much superior; we shall therefore pass on to notice the important improvements in this branch of dyeing made by Dr. Bancroft, and which have obtained the approbation of the most eminent chemists, British and foreign.

191. Dr. Bancroft was struck with the thought that for a whole century no improvements had

been made in the art of dyeing scarlet. On this object he seems to have fixed his mind, and, about the year 1786, he instituted a set of experiments which were attended with the most gratifying

success.

192. Having, by frequent affusions of boiling water, extracted the whole of the coloring matter from powdered cochineal, he found that the addition of a little potash to the sediment, and a fresh quantity of boiling water, extracted a new portion of coloring matter, equal to about oneeighth of what had been given out to the pure water. He repeatedly extracted this coloring matter by means of potassa, and afterwards dyed small pieces of cloth scarlet with it, which he found similar to others dyed with cochineal. It was in the course of these enquiries that he perceived scarlet to be a compound color, consisting of about three-fourths of pure crimson, and onefourth of pure bright yellow. He conceived, therefore, that when the natural crimson of the cochineal is made scarlet, by the usual process, there must be a change produced, equivalent to a conversion of one-fourth of the coloring matter of cochineal from its natural crimson to a yellow color. From this he concluded that there might be a great saving of cochineal, by substituting a cheaper substance, which, at the same time, might yield a better yellow color. It was therefore his object to combine with this crimson or rose color, a suitable portion of a lively golden yellow, capable of being permanently fixed, and reflected by the same basis. This yellow Dr. Bancroft found in quercitron bark; and ascertained that it possessed the advantage of being not only the cheapest, but the brightest of all the yellows he had tried.

193. For the purpose of diminishing the quantity of cochineal employed in producing a scarlet dye, Dr. Bancroft made a number of experiments under the authority of government. In these experiments, the mordant used was the common dyers' spirit, or the nitro-muriate of tin, but he found that they were not attended with the advantages which he expected. In some of his earliest experiments, he remarks, that the solution of tin by means of sulphuric acid destroys the cochineal color, and this led him to reject the use of this acid, till accident brought him to dissolve a quantity of tin in muriatic acid, combined with one-fourth of sulphuric acid. The application of this solution in dyeing, was not accompanied with the corrosive effects of the muriate and nitro-muriate which he had employed in the experiments, and which proved unsuccessful. After trying different proportions of these acids, he found the following to answer best. In a mixture of two pounds of sulphuric acid of the ordinary strength, and about three pounds of muriatic acid, he dissolved about fourteen ounces of tin. The muriatic acid is first poured upon a quantity of granulated tin in a suitable vessel, and the sulphuric acid is added by degrees. This solution is more quickly effected by means of a sand heat; it is perfectly colorless, and may be kept for years without precipitation. It has double the power of the common dyers' spirit; and is produced at about one-third of the expense. VOL. VII.

It also raises the colors more than even the tartrate of tin; and does not incline the cochineal crimson to the yellow shade.

194. In using this solution as a mordant, to produce the compound scarlet color, Dr. Bancroft advises the following process. Nothing, says he, is necessary, but to put the cloth, suppose 100 pounds, into a proper tin vessel, nearly filled with water, in which has been mixed eight pounds of the murio-sulphuric solution of tin; and, having brought the mixture to a boiling heat, about 100 pounds of cloth are immersed and turned through it as usual, by the winch, for a quarter of an hour. Then the cloth is removed, and four pounds of cochineal and two pounds and a half of quercitron-bark, both powdered, are introduced and well mixed. After this, the cloth is returned into the bath, the liquor is made to boil, and the cloth is turned as usual for fifteen or twenty minutes, by which time, in general, the color will be properly raised and the bath exhausted, when the cloth is taken out and rinsed in the ordinary way.

By this method the time, labor, and fuel, necessary for filling and heating the boiler a second time are saved, the process finished much sooner than in the common way, and there is a saving of all the tartar, as well as of two-thirds of the cost of spirit, or nitro-muriatic solution of tin, which, for dyeing 100 pounds of wool, commonly amount to ten shillings, whereas eight pounds of the murio-sulphuric solution cost only about three shillings. There is, besides, a saving of at least one-fourth of the cochineal usually employed, and the color produced does not prove inferior in any respect to that dyed with much more expense and trouble in the ordinary way.

195. When a rose color is wanted, it may be readily obtained in this way, only omitting the quercitron bark, instead of the complex method of first producing a scarlet, and then changing it to a rose by the volatile alkali contained in stale urine, set free by potash or by lime; and should any one still choose to continue the practice of dyeing scarlet without the quercitron bark, it is only necessary to employ the usual proportions of tartar and cochineal, with a suitable quantity of the murio-sulphate of tin, which, while it is cheaper, is much more effectual than the dyers' spirit.

196. The scarlet, produced from cochineal crimson and quercitron, is also attended with this advantage, that it may be dyed upon wool and woollen yarn, without any danger of its being changed to a crimson color by the process of fulling, which always happens to scarlet dyed in the common way. Indeed, this last is nothing but a crimson or rose color, rendered yellow by some particular action of the tartaric acid; and is hence liable to be reduced to crimson by many chemical agents, especially by soap, alkaline salts, salts of lime, &c. But where the coloring matter of cochineal is applied and fixed merely as a crimson or rose color, and is rendered scarlet by adding a very permanent yellow, capable of resisting the strongest acids and alkalis, when used with solutions of tin, no such

2 R

change takes place, because the color given by cochineal, having never ceased to be crimson, cannot be rendered more so, and therefore cannot suffer by those impressions or applications which frequently change or spot scarlets dyed according to the ordinary practice. There is also a remarkable property attending the compound scarlet dyed with cochineal and quercitron bark, viz. that if a piece of cloth dyed in this way be compared with another piece dyed by the usual process, both will by day-light appear exactly of the same shade; but, if they be afterwards compared together by candle-light, the former will appear at least several shades higher and fuller than the latter;-a circumstance of some importance, when it is considered how much this and other gay colors are worn and exhibited by candle-light, during a considerable part of the year.

197. To illustrate more clearly, continues Dr. Bancroft, the effects of the murio-sulphuric solution of tin with cochineal in dyeing, I shall state a very few of my numerous experiments therewith; observing, however, that they were all several times repeated, and always with similar effects.

1st, I boiled 100 parts of woollen cloth in water, with eight parts of the murio-sulphuric solution of tin, during the space of ten or fifteen minutes; I then added to the same water four parts of cochineal, and two parts and a half of quercitron bark in powder, and boiled the cloth fifteen or twenty minutes longer; at the end of which time it had nearly imbibed all the color of the dyeing liquor, and received a very good, even, and bright scarlet. Similar cloth dyed of that color at the same time in the usual way, and with a fourth part more of cochineal, was found upon comparison to have somewhat less body than the former; the effect of the quercitron bark in the first case having been more than equal to the additional portion of cochineal employed in the latter, and made yellow by the action of tartar.

2d, To see whether the tartrite of tin would, besides yellowing the cochineal crimson, contribute to raise and exalt its color more than the murio-sulphate of that metal, I boiled 100 parts of cloth with eight parts of the muriosulphuric solution, and six parts of tartar, for the space of one hour; I then dyed the cloth, unrinsed, in clean water, with four parts of cochineal, and two parts and a half of quercitron bark, which produced a bright aurora color, because a double portion of yellow had been here produced, first by the quercitron bark, and then by the action of tartar upon the cochineal coloring matter. To bring back this aurora to the scarlet color, by taking away or changing the yellow produced by the tartar, I divided the cloth whilst unrinsed into three equal parts, and boiled one of them a few minutes, in water slightly impregnated with potassa; another in water with a little ammoniac; and the third in water containing a very little powdered chalk, by which all the pieces became scarlet; but the two last appeared somewhat brighter than the first, the ammoniac and chalk having each rosed the cochineal color rather more advantageously

than the potassa. The best of these, however, by comparison, did not seem preferable to the compound scarlet dyed without tartar, as in the preceding experiment; consequently this did not seem to exalt the cochineal color more than the murio-sulphate of tin; had it done so, the use of it in this way would have been easy, without relinquishing the advantages of the quercitron yellow.

3d, I boiled 100 parts of woollen cloth with eight parts of the murio-sulphuric solution of tin, for about ten minutes, when I added four parts of cochineal in powder, which, by ten or fifteen minutes more of boiling, produced a fine crimson. This I divided into two equal parts, one of which I yellowed, or made scarlet by boiling it for fifteen minutes with a tenth of its weight of tartar in clean water; and the other, by boiling it with a fortieth part of its weight of quercitron bark, and the same weight of murio-sulphuric solution of tin; so that in this last case there was an addition of yellow coloring matter from the bark, whilst in the former no such addition took place, the yellow necessary for producing the scarlet having been wholly gained by a change and diminution of the cochineal crimson; and the two pieces being compared with each other, that which had been rendered scarlet by an addition of quercitron yellow, was, as might have been expected, several shades fuller than the other.

4th, I dyed 100 parts of woollen cloth scarlet, by boiling it first in water with eight parts of murio-sulphate of tin, and twelve parts of tartar, for ten minutes, and then adding five parts of cochineal, and continuing the boiling for fifteen minutes. This scarlet cloth I divided equally, and made one part crimson, by boiling it with a little ammoniac in clean water; after which I again rendered it scarlet, by boiling it in clean water, with a fortieth of its weight of quercitron bark, and the same weight of murio-sulphate of tin; and this last, being compared with the other half to which no quercitron yellow had been applied, was found to possess much more color, as might have been expected. A piece of the cloth, which had been dyed scarlet by cochineal and quercitron bark, as in the first experiment, being at the same time boiled in the same water with ammoniac, did not become crimson, like that dyed scarlet without the bark.

In this way of compounding a scarlet from cochineal and quercitron bark, the dyer will at all times be able, with the utmost certainty, to produce every possible shade between the crimson and yellow colors, by only increasing or diminishing the proportion of bark. It has indeed been usual at times, when scarlets approaching nearly to the aurora color were in fashion, to superadd a fugitive yellow either from turmeric, or from what is called young fustic; but this was only when the cochineal color had been previously yellowed as much as possible by the use of tartar, as in the common way of dyeing scarlet; and therefore that practice ought not to be confounded with my improvement, which has for its object to preclude the loss of any part of the cochineal crimson, by its conversion towards yellow color, which may be so much more cheaply

obtained than the quercitron bark. By sufficient trials, I have satisfied myself that the cochineal colors, dyed with the murio-sulphuric solution of tin, are in every respect at least as durable as any which can be dyed with any other preparation of that metal; and they even seem to withstand the action of boiling soap lie somewhat longer, and therefore I cannot avoid earnestly recommending its use for dyeing rose and other cochineal colors, as well as for compounding a scarlet with the quercitron bark.

OF DYEING CRIMSON.

198. The different processes employed for obtaining the various shades of crimson, from the deepest to the lightest, may be reduced to two. Either the shade of crimson required is given to cloth previously dyed scarlet, or the cloth is at once dyed crimson. Alum, salts with earthy bases, and fixed and volatile alkalis, have the property of changing the color of scarlet to crimson, which is the natural color of cochineal. Nothing more, therefore, is necessary, than to boil cloth dyed scarlet for about an hour in a solution of alum, proportioned in strength to the deepness of the color desired. But as other salts with earthy bases have the same property, and water contains more or less of these salts, whence it gives a proportionate rosy tinge to scarlet passed through it, particularly if it be worn, the quantity of alum necessary to obtain a crimson varies according to the nature of the water employed; and, when well charged with these salts, it will answer the purpose of itself, without the addition of alum. If a piece of scarlet have any defects, it is most convenient to convert it into a crimson.

199. Hellot says, that he has tried soap, soda, potassa, and crude potassa; that all these substances produced the crimson desired, but saddened it, and gave it less lustre than alum. Ammonia, on the contrary, produced a very good effect; but, as it evaporates quickly, a consider able quantity must be put into the bath a little more than warm, a little ammoniacal muriate, or sal ammoniac, and common potash. By this method the cloth instantly took a very bright rosy color. He thinks that it heightens the color so much as to render less cochineal necessary. But M. Poerner, who gives the same process, directs the scarlet to be left twenty-four hours in a cold solution of potassa and ammoniacal muriate.

200. To dye crimson at once, a solution of two ounces and a half of alum, and one ounce and a half of tartar, to every pound of cloth, is used for the boiling: and the cloth is afterwards dyed with an ounce of cochineal. Solution of tin is commonly added, but in less proportion than for scarlet. The processes employed vary greatly, according as the shade required is deeper or lighter, or more or less distant from scarlet. Common salt is also used for the boiling by some dyers. For saddening crimsons, and giving them more bloom, archil and potassa are frequently used, but the bloom thus imparted is not permanent. Sometimes the boiling for crimson is made after a scarlet reddening, by adding tartar and alum: and it is said, that the

wine soup color has more bloom, if both its boiling and reddening be made after scarlet, than when it is dyed in a fresh bath. For these colors the wild cochineal may be used instead of the fine, but in greater quantity. The reddening which has been used for crimson may also be employed for purples, and other compound colors.

Both scarlets and crimsons in half-grain are made by substituting madder for half the quantity of the cochineal, giving the same boiling as for scarlet in grain, and following in other respects the processes for reddening the scarlet or crimson. Other proportions of madder may be used instead of half, according to the effect desired. The common madder red also acquires a greater lustre, when its boiling is made after a reddening for scarlet.

201. In silk the grain crimson, produced by cochineal, is distinguished from false crimson, which is obtained by Brasil-wood. Silks that are intended to be dyed crimson with cochineal, should not be boiled with more than twenty pounds of soap to 100 pounds of silk, as the slight yellow cast which silk has, when only so far scoured, is advantageous to the color. After the silk has been well cleansed from the soap, it is to be put into an alum liquor of the full strength. In this it is commonly left from the evening till the next morning; it is then washed, and twice beetled at the river. In preparing the bath, an oblong boiler is filled with water, to about onehalf or two-thirds; and, when the water boils, white galls powdered are thrown in, from half an ounce to two ounces for every pound of silk. After boiling a few moments, from two to three ounces of cochineal, powdered and sifted, for every pound of silk, according to the shade required, are put in, adding afterwards an ounce of tartar, to every pound of cochineal; and, when the tartar is aissolved, an equal quantity of the solution of tin. This solution ought to contain more tin than that used for scarlet, otherwise the colors will be too bright. Macquer directs this solution to be made with sixteen parts of nitric acid, two of ammoniacal muriate, as much fine grain tin, and twelve of water These ingredients are mixed and the boiler is filled up with cold water. In this the silk is immediately dipped, and turned on the skein sticks till it appears to be of a uniform color. The fire is then increased, and the bath made to boil for two hours, turning the silk from time to time. After this the fire is put out, and the silk put into the bath, where it is kept a few hours longer. The silk is afterwards washed at the river, twice beetled, wrung and dried. When crimsons are to be browned, they must be passed, after having been washed, through a solution of sulphate o. iron, more or less strong according to the shade required. If it should have a yellow tinge, the solution must be charged with a greater or less proportion of decoction of fustet or Venus's sunach. White galls should be chosen, because black ones would dull the color of the crimson; and even too large a quantity of the white will produce the same effect. Macquer says, that the galls serve only to increase the weight of the silk: yet their general effect is to render colors

more permanent, and they are essentially ne cessary for crimsons that are intended to be browned. Vinegar is employed as a test in distinguishing grain crimsons from false: but it will not detect colors obtained from Brasil-wood, if they be fixed by means of solution of tin; for in this case they resist vinegar as well as those made with cochineal. A very small quantity of solution of tin is, therefore, put into the bath for dycing silk crimson. If the same process as that for dyeing wool scarlet were employed, the silk would lose its bloom, and acquire only a faint color. Macquer and Scheffer have, however, detailed processes which differ from it only in a few circumstances, for dyeing silk rose and poppy colors by solution of tin, used cold, that its action on the silk might not be too powerful.

202. Brasil-wood is used for dyeing silk what is called false crimson, to distinguish it from that produced by cochineal, which is much more permanent. For this process the silk should be boiled with soap, in the proportion of twenty pounds of the latter to 100 pounds of the former, and afterwards alumed. Less aluming is required for this than for grain crimson. Having washed it in running water, it is dipped in a bath, more or less charged with Brasil juice, according to the shade to be given. In the preparation of the bath hard water is preferable to soft, as it produces with the dye-stuffs a fuller crimson. Washing the silk in hard water will produce nearly the same effect. In order to make false crimson deeper, or dark red, a decoction of logwood is added to the Brasil bath, after the silk has been impregnated with the latter. A little alkali may also be put in according to the shade required. But to imitate poppy or fire color, the silk must have an anotta ground, even deeper than when it is to be dyed with carthamus: after which it is washed, alumed, and dyed with the decoction of Brasilwood, to which a small portion of soap is generally added. We might here enumerate several other processes for imparting the crimson color, but the above, with what we have said respecting the dyeing of reds in general, and of scarlet in particular, render it unnecessary to enlarge.

OF DYEING YELLOW.

203. Of Dyeing Wool Yellow.-The yellow communicated to wool by weld has little permanency, if the wool be not previously prepared by some mordant. For this purpose alum and tartar are used, by means of which this plant gives a very pure and durable yellow. For the boiling, which is managed in the common way, Hellot advises four ounces of alum to every pound of wool, and only one ounce of tartar; many dyers, however, use half as much tartar as alum. Tartar renders the color paler, but more lively. The weld is boiled in a fresh bath, enclosing it in a bag of thin linen, and keeping it from rising to the top by a heavy wooden cross. Some dyers boil it till it sinks to the bottom of the copper, and then let a cross down upon it: others, when it is boiled, take it out with a rake, and throw it away. From three to four pounds of weld, and,

in some instances less, are allowed for every pound of stuff; but the quantity must be regulated by the depth of shade required. Some dyers add a little quick-lime and ashes, which are found to promote the extraction of the coloring matter, and at the same time heighten the color; but they thus render it more liable to the action of acids.

204. Both lighter and brighter shades may be obtained by dyeing after deeper ones, adding water at each dipping, and keeping the hath boiling: but light shades procured in this way are not so lively as when fresh baths are used, proportioning the quantity of weld to the depth of the shade intended to be procured. If common salt be added to the weld bath, it renders its color richer and deeper: sulphate of lime, or gypsum, also deepens it: but alum renders it paler and more lively; and tartar, still paler. Sulphate of iron or vitriol makes it incline to brown.

205. According to Scheffer, by boiling the stuff for two hours with one-fourth of its weight of a solution of tin, and the same proportion of tartar, and then washing it and boiling it for about a quarter of an hour with an equal weight of weld, it will assume a fine yellow, which, however, will not penetrate the substance of cloth.

206. Poerner recommends a process similar to that used in dyeing scarlet, by which means the color is brighter and more permanent.

207. Since the introduction of the use of quercitron bark, the process of dyeing yellow has been much simplified, as may be seen from the following directions of Dr. Bancroft on the subject. He proposes that the bark should be boiled with about its own weight, or one-third more of alum, in a suitable quantity of water, for about ten minutes.

208. The substances to be dyed are previously scoured, and then immersed in the bath, observing to give the higher colors first, and afterwards the paler straw colors. By this cheap and expeditious process, colors which are not wanted to be of a full or bright yellow, may be obtained. The color may be considerably heightened by passing the unrinsed stuff a few times through hot water, to which a little clean powdered chalk, in the proportion of about a pound and a half for every 100 pounds of stuff has been previously added. The hark, when used in dyeing, being first reduced to powder, should be tied up in a thin linen bag, and suspended in the liquor, so that it may be occasionally moved through it, to diffuse the coloring matter more equally.

209. But although this method possesses the advantages of cheapness and expedition, and is sufficient for communicating pale yellows; to obtain fuller and more permanent colors, the common mode of preparation ought to be preferred. The stuff should be boiled for about one hour, or an hour and a quarter, with onesixth, or one-eighth of its weight of alum, dissolved in a proper proportion of water. The stuff is then to be immersed, without being rinsed, into the dyeing bath, with clean hot water, and about the same quantity of powdered