I may mention as an instance that it is recorded that Alexander the Great wore a pectoral of printed linen, probably not better, and certainly not nearly so gaudy, as those Turkey red handkerchiefs which we are accus. tomed to send to Brazil and Mexico to adorn the lowest classes of the population.

The British calico-printing trade is now of great magnitude. It consumes one-seventh of all the cotton which is imported into this country. Perhaps this may not give you an idea of its largeness, and therefore I will put it in another way. There are printed annually, in this country, thirty-one millions of pieces of calico, which is equal to 450,000 miles. This is also a method of indicating the largeness of the subject, which it is difficult to understand; supposing you were to measure the calico printed annually in Great Britain by a gigantic standard measure-take the diameter of the earth as your "yard measure," with which you are to measure the calicos printed in Great Britain in one year,-you would require to stretch it along the diameter of the earth fifty-six times; or, if you were to wrap the whole world round with a bandage of the calico printed annually in this country, you would envelope it in nineteen folds. You will hence see that it is an art of great magnitude, and that it is one which, therefore, justly draws our attention, not only on account of its importance as regards itself, but also (and this, as you will observe by the programme, is mainly the subject of my lecture to-day) on account of the arts which it brings into its train, and the important manufactures which it creates and helps to sustain. To-day's lecture, therefore, is directed to these arts, and to the preliminary processes in the printing of calico.

The preliminary processes are numerous. I will merely enumerate them in their names just now. There are six of them.

There is, first, the bleaching of the calico; second, the application of the mordants, or what Pliny has called the "excipient drugs," which drag the colour out of the bath and fix it upon particular parts of the fabric; third, the resists or discharges, which keep the calico white at particular parts, or produce a white pattern; fourth, the ageing, which will explain itself when we come to it; fifth, the dunging or the fixing of the mordants; and sixth, the dyeing.

I commence with the bleaching. The bleaching of the calico is an exceedingly important part of the process. On the right hand side of that small table you will see the calico as it is delivered to the printer from the weaver. It is of a grey colour, and not at all adapted for the purpose of the printer. It contains the flour and the grease which the weaver uses in his operation. It also contains a natural resin, which prevents the calico from taking on the colour, and it is necessary that all this should be removed, and that the calico should be converted from that dirty grey into a white before the calico printer can use it. Well, up to the last two years of the last century -to 1798,-the bleaching of calico was an extremely formidable operation. It required for its completion from the month of March to the month of September. After the grey calico was boiled in alkaline lyes to take out the grease of the weaver and the resin of the natural calico, it was spread out in vast fields, and was exposed to the action of the sun and moisture, being occasionally watered, first with water, and then with buttermilk; and in this way a true combustion took place. Under the influence of the sun and the moisture the oxygen united with the colouring matter and burnt it; and the colouring matter was thus burnt out of the cloth, and the cloth became white. In this combustion, however, part of the cloth itself was burnt, and the texture was often red; but the greatest evil was this,-that every rinting works, in order to bleach its calico for quired vast estates in connection with the works ich to spread out the calico to the action of the

sun and air; or in absence of these, the printers sent the calico to Holland to be bleached. The bleaching, therefore, became an extremely expensive part of the operation. Towards the end of the last century it was discovered that bleaching might take place in a much more easy way; but the circumstances that led to this discovery are so interesting, that I would not hesitate, if we had not so much before us, to give you a description of the manner in which this discovery resulted. I will do so in a few words. France, during the revolution, was shut out from receiving a supply of soda, which was used to dissolve out the resin of the calico, from Spain, where it was manufactured under the name of barilla, being derived from the ashes of sea-weed. Our cruisers were vigilant, and we shut out this supply of soda from France. The consequence was that the soap-boilers of Marseilles were nearly ruined, and the manufacturers of calico also suffered extremely. Accordingly, the government offered a high reward to any person who would discover how to make soda from seasalt. Sea-salt, as you are aware, contains the metal sodium, but united with chlorine and not carbonic acid. It was sagaciously thought that soda might be made out of it; and it was ascertained that, some time before, Leblanc, a private manufacturer, had actually practised a method for converting this common salt into soda. The process is a complex one. I cannot describe it to you further than by stating that the first step is to treat the common salt with sulphuric acid, which drives off the hydrochloric or muriatic acid, and leaves sulphate of soda behind. This is then treated with carbonate of lime, and is converted into carbonate of soda. For a long time the muriatic acid from the common salt went out through tall chimneys into the atmosphere, and devastated the country by destroying vegetation. It is this of which Lord Derby complained in the House of Lords the other night, and which led him to move for a Committee to inquire in what manner manufacturers can be restrained from sending these injurious gases into the atmosphere. Lancashire alone converts 135,000 tons of common salt into carbonate of soda every year. This hydrochloric acid was for a long time lost, but it was soon found to consist of chlorine and hydrogen; and this chlorine possesses strongly bleaching powers. I have here some of this chlorine dissolved in water. If I add to it a colouring matter such as this indigo, you will see that the colour quickly disappears. The colour of the indigo is removed from it.

When it was found out that chlorine had such a power of destroying colour, persons began to think that it might be used as a bleaching agent, instead of exposing the calico for such a number of months to the action of the sun and air. Now, the mode in which this bleaches the colour is by the decomposition of water. Water, as you are aware, consists of hydrogen and oxygen, and the chlorine has a great love for the hydrogen and desires to unite with it; and so it takes away the hydrogen from the water, and forms hydrochloric acid with it; and the oxygen liberated from the water goes and burns away the colouring matter. You know that ordinary combustion in a fire-place is the oxygen uniting with the material of the fire. So here, the oxygen of the water, being set at liberty by the hydrogen uniting with the chlorine, burns the colouring matter and destroys it, just as the oxygen burnt the colouring matter when the calicoes were exposed to the air in the old process of bleaching.

After a time it was found that if this chlorine, which is a gas, was passed over lime it was absorbed by the lime, and formed what we are now so familiar with as bleachingpowder, and that this bleaching-powder bleached just as well as chlorine did, and without having the irritating smell and the irritating action on the lungs which are common to chlorine. As soon as the property of bleaching-powder was discovered, an extraordinary impulse was given to the process of bleaching. After the resinous and fatty matters

CHEMICAL NEWS, June 21, 1862.

have been removed from the grey cloth, it is treated with a weak and clear solution of chloride of lime. In this action the chlorine, desiring to unite with the calcium of the lime, accomplishes this by liberating the oxygen which destroys the colouring matter. From beginning to end of the operation of bleaching only five days are necessary instead of the months which were formerly required. Five days are occupied in converting this grey cloth into white cloth, to make it ready for the calico printer, who is generally his own bleacher. The cloth is first singed by being passed over a red hot cylinder, as you see represented here in the second diagram. This is done tolerably slowly, in order to take away the fibres and clean them from the surface. The texture, however, does not get injured. After being passed over the red hot cylinder it appears in this state, a little browner. It is now boiled in lime. The lime loosens the resins, and forms a compound of resin and lime on the cloth. This is boiled with dilute sulphuric acid in order to dissolve out the lime and liberate the resin. It is now boiled with a solution of carbonate of soda-the substance is made from common salt, and it renders the grey calico much whiter than it was before. After that it is passed through a solution of chloride of lime. There are one or two boilings which I need not enter into, but the mode in which the boiling is effected is interesting. There is a diagram representing the "bowk," as it is called, or the vessel in which the boiling of the soda and the lime takes place. You see the calico is coming in by machinery, and a boy is represented spreading it along on the floor of the caldron. In this there is placed, after the boy of course has departed, a quantity of water and a quantity of carbonate of soda; and there is an elegant fountain arrangement which cannot be represented there on account of the boy being present, by which the hot fluid is thrown up to the top through these tubes. It is prevented by the arch at the top from getting out, and is thrown in a fountainshape over the cloth below, so that it is continually percolating through it, and coming down over it; and in that way the resinous matter is completely removed from the cloth. The latter is now passed through a solution of bleaching powder-chloride of lime, consisting of lime and chlorine. The chlorine has a great desire to unite with the calcium, the metal of the lime, and form chloride of calcium, and the oxygen being set at liberty burns away the colouring matter of the calico and bleaches it. There would appear to be no decomposition of the water, as in the case of bleaching with chlorine in the form of a gas. All these operations-boiling in lime, boiling in soda, steeping in the bleaching liquor, and all the operations of washing and drying, occupy only five days from the beginning, and it is carried on in works of small extent. No estates are necessary in connection with the works. The verdure of miles of country is no longer defaced with outstretched calico bleaching in the sun.

Before parting from this subject, let us pause here to consider how this method of bleaching has raised up several important manufactures.

The soda-ash trade is of enormous extent, and is now carried on by extensive manufacturers to supply materials for bleaching and washing soda. Sulphuric acid is necessary in its production, as I told you; so that the price of sulphur regulates the price of calico. The price of sulphur also regulates the price of other materials, such as soda, and of glass, in making which soda is much used. About twenty years ago, as many of us recollect, the King of Naples was persuaded by a Marseilles firm that it would augment the small revenues of his country very much if he gave that firm a monopoly in all the Sicilian sulphur. They imme. diately raised the price of sulphur from 5l. to 147. a ton. Our calico trade, soap trade, glass-works, and various other interests were soon affected by this proceeding, and the consequence was that our government were obliged to take some of the Sicilian sulphur and convert it into gunpowder, with which our fleet went to Naples, threatening

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to bombard that place unless the monopoly was abolished. The Neapolitan Government did not like the return of their sulphur in this form, and so they permitted the export on the old terms, and our manufactures again flourished. But what was the consequence of this short monopoly. Naples has lost enormously by it. Like all foolish experiments of this kind on trade, it had a most disastrous effect upon those who made it, and it has had a most beneficial effect upon our sister country, Ireland. The skill of our chemists was brought into play to see whether they could not discover sources of sulphur in our own country. We found an abundant source of sulphur in iron pyrites, which exists in such large quantities in Wales and Ireland, and also in Spain and Portugal. The consumption of Sicilian sulphur is thus much reduced.

There are one or two other things in connection with these arts which I must allude to very shortly, as my time is going on.

In the manufacture of this bleaching powder, where chlorine is made, hydrochloric or muriatic acid is boiled with peroxide of manganese, and this produces chlorine. All the manganese was, until recently, wasted after the operation. The chloride of manganese was a waste product, and there were no means discovered for getting back this expensive salt-for producing again the peroxide of manganese after it had been boiled with hydrochloric acid. A beautiful plan has been recently invented, but which will be appreciated chiefly by the chemists present. The protoxide of manganese produced by precipitation from the chloride will not absorb oxygen from the air to form peroxide of manganese, but carbonate of manganese, MnOCO2, when roasted in air, allows its carbonic acid to be displaced by the oxygen of the air, and peroxide of manganese, MnO2, is thus produced. I here take a little of this carbonate of manganese which is a white or nearly white substance; if I gently roast it, stirring it at the same time, you see that it becomes the ordinary brown oxide of manganese, the carbonic acid having been displaced by the oxygen. In this way all this manganese, or, at least, the greater part of it, is recovered.

There is another interesting process for producing bleaching powder, which has been made within the last few years, and which my chemical friends here will fully appreciate if they are not acquainted with it already, but which I fear I shall scarcely make intelligible to a general audience. It was devised by Mr. Shanks, of St. Helens. First common chrome ore is roasted with lime, and is thus converted in the usual way into chromate of lime,-this yellow salt which I have here. The chromic acid in this compound contains oxygen. The chromate of lime is boiled with hydrochloric acid, the hydrogen of which is taken away by the oxygen of the chromic acid. Chloride of chromium is formed, and part of the chlorine is liberated which combines with the lime to form bleaching powder. The chloride of chromium remains in solution. This chloride of chromium is again treated with lime, and precipitates oxide of chromium with which we started, and chloride of calcium remains in solution. Now, this oxide of chromium is merely mixed with more lime and roasted again in the air. It abstracts oxygen from the air and forms again chromate of lime, another of the substances with which we started; so that by this beautiful process the oxygen is continually taken from the air, forced to unite with the hydrogen of the hydrochloric acid, and the chlorine, entering the lime, forms bleaching powder. The process is, therefore, elegant, but is not yet extensively employed.

I now pass to the subject of mordants. The application and fixation of mordants form the most important parts of the preliminary operations of the calico printer's art. The mordant is the material which is fixed upon the cloth, and which has the power of taking the colouring matter out of the drug. You will find that among these specimens here I have a pattern printed upon this cloth. The pattern is printed with what are called the mordants. These mor

dants are generally oxides of iron, oxides of tin, or oxides of aluminium or alumina, most of them being oxides which play the part in the operation of weak acids. Now you will understand what the operation of a mordant is, if I give you some elementary experiments upon this cloth. I dip the cloth into a mordant which, in this instance, is a solution of oxide of iron. Now, the object of the mordant is to enter into the material, and by combining with the colour to render it insoluble within the pores of the cloth. I have got the mordant within the pores of the cloth, and if it be immersed in a colour-giving liquid, the mordant will combine with it and render the colour insoluble within the pores of the cloth. I now dip it in this solution, and you see that it immediately becomes of a deep blue. In this case I have used prussiate of potash. That blue colour is rendered insoluble in the cloth, and will bear washing. By means of these mordants it is possible to render insoluble the colour, which would otherwise be soluble and wash out. It penetrates the pores of the cloth, and the action of the mordant being to render it insoluble, the colour remains.

The art of the calico printer, however, consists in trying to produce several colours at one operation. I will represent that also to you in an elementary way. I have here the means by which I may produce two colours by one operation. In this case I have copper in one part, and iron in another. If I add a little acid to this and stir it, and then put the cloth into the solution, I have no doubt that after a little time you will see that one part will come out of a mahogany colour, and the other, as it gets wet, will become blue. You see in this case we are producing two different colours by one operation. We can always manage, by a little chemical artifice, to get different colours out of the same material.

The calico printer's art, however, would not be contented with such a simple and elementary experiment as that. He sometimes desires to produce twenty colours instead of two colours. You must follow me carefully in order to understand how he gets such a great success in his art. I must now stop my explanation of the action of mordants by interpolating it with an important operation which he performs, and which, though simple, is important. I will here try to print a cross on this cloth with cochineal. You see that I produce nothing but an ugly smear. The colour runs aside all over the cloth as it would do upon blotting paper, and I cannot produce the cross that I desire because the colour runs about and produces no definite character. The calico printer has to overcome this difficulty. He must print on his mordant in such a way that it may not run, and so that the pattern may be precise, as you see on these print patterns, and that there may be no running at the edges. Now, he effects this by a very simple operation. He puts a certain quantity of gum into the substance, and the adhesiveness of this gum prevents it from running, so that I can now produce exactly any figure which I desire. I produce here a cross, and this cross will be as precise as I happen to paint it on, because the gum in this case prevents the liquid from running at the edges of the cloth. It is by mixing it with gum, or "thickeners," as it is termed, that a precise pattern is produced. Now this thickening has in itself created quite a set of new works. The making of thickeners for the calico printer has caused a large trade to arise in the manufacture of "British gum, as it is termed. Acetate of iron and acetate of alumina are the two common mordants which are used. These mordants are thickened and mixed in the necessary proportions which I shall presently explain, and are printed in the desired pattern on the cloth. The most elementary way of doing this is by a process which was followed in Hindostan long ago. The pattern was cut out on a block, and then the thickened mordant was taken upon an elastic drum and spread on the block, and the pattern of the block was then printed on the cloth. But as

mechanical contrivances became improved, ..e process of printing by machinery was adopted. We will show you the machine in the next lecture as we are coming more upon that part of the subject then; but here is the means by which it is done. The impression is made upon a roller like these. The rollers are generally much larger than this. They are so made to work, by mechanical contrivances, one into another, that they will produce from five to twenty impressions by acting in harmony with one another so as to form a unity in the design. It is a beautiful contrivance of the mechanist, but it is not a chemical subject upon which we can at all dwell. Now, before completing the subject of mordants I have still another thing to bring before your attention, and that is the resists and discharges. There would be no beauty in our designs were we not able to preserve the white portions upon them, either to introduce new colours afterwards, or to produce certain desired patterns. For instance, in this yellow pattern you observe these whites which are left quite white, although they have been in the bath. Now, the resists or discharges are merely means of preventing the mordant fixing itself to particular parts of the cloth, where it is not desired to have the colour produced. Certain acids, oxalic acid, lime juice, or citric acid, are placed upon the parts where these oxides are not desired to fix themselves, so that while the oxides run over the whole of the rest of the cloth they meet with these resists where they have been applied, and those parts come out uncoloured. This is a matter which may be readily understood.

One of the most important of these resists or discharges is oxalic acid. This was an expensive substance-so expensive that the consumption throughout the whole world was supposed to be recently only fifteen tons weekly, It is the acid which exists in the common sorrel, and is often called salt of sorrel. It has been made, until within the last year or two, by acting upon starch or sugar with nitric acid. Now, starch and sugar are what some chemists call hydrates of carbon; that is to say, they are compounds of carbon in which hydrogen and oxygen are present in the same proportion as in water. The starch and sugar are themselves expensive materials, and the nitric acid is still more expensive. There is, however, a hydrate of carbon which is very cheap. It is a waste material which we have not known what to do with until about a year ago. This is common sawdust. It is of the same chemical composition as starch or sugar. When sawdust is thrown upon a fire it unites with oxygen, burns, and produces carbonic acid. If this oxidation be stopped half way oxalic acid is produced. Oxalic acid is half way between the oxidation of any of the hydrates of carbon and complete oxidation for the formation of carbonic acid. Now, this sawdust within the last year or two has been made to produce oxalic acid by a beau tiful manufacture. A process often employed to produce imperfect oxidation is to heat the organic body with hydrate of potash. In this case the water of the hydrated alkali is decomposed, the oxygen entering into the organic body and decomposing it, while the hydrogen escapes either free or sometimes carrying off some carbon in its flight. Messrs. Roberts and Dale, of Manchester, have followed this plan very successfully. Soda being a substance which is much cheaper than potash, it naturally suggested itself as equally fit for the purpose of producing this partial combustion, but practically it is found that it does not produce oxalic acid by its action on sawdust. Potash which will produce it is too dear to be employed exclusively. It has been found, however, that two equivalents of hydrate of soda, and one equivalent of hydrate of potash, answers admirably. It is curious that soda will not do alone. The sawdust is mixed with these quantities, and allowed to remain in contact for a little time, and it assumes this brown appearance. It is now heated for three or four hours at a temperature of 400° in shallow pans having

CHEMICAL NEWS,

June 21, 1862.

cast-iron bottoms; and now it gradually gets into an intermediate product, but only contains about two or three per cent. of oxalic acid. It is now heated still further, and is converted into oxalic acid in combination, of course, with soda and potash, forming the oxalates of those alkalies. Here comes a beautiful process, one which is still mysterious to the chemist. This mixture of oxalate of potash and oxalate of soda is thrown upon a filter, and a solution of carbonate of soda is passed through it, and probably from the oxalate of soda being more insoluble than oxalate of potash, the oxalate of soda remains behind, while carbonate of potash filters through. This oxalate of soda is now mixed with lime and forms oxalate of lime, liberating the soda. The soda is added to the potash which came through in the filtering. Sulphuric acid is now added to the oxalate of lime. Sulphate of lime is thus formed, and oxalic acid remains dissolved in the water, from which it is afterwards crystallised, and you get this beautiful material, oxalic acid. Two pounds of sawdust will yield one pound of oxalic acid. Roberts and Dale, who have perfected this process in Manchester, now make nine tons per week; and the price of it has fallen from fourteen or fifteen pence a pound, to eightpence or ninepence a pound.

Now, I want to show you the application of these acids -oxalic, tartaric, and the various others-to the purpose of discharges, You can understand these readily as resists. They protect the white places and keep them uncoloured; but you may not so readily understand how they act as discharges. A "discharge" is a term applied to an agent which is used for the removal of the colour from any part of the cloth when it has once been dyed. Suppose I want to take away some of this colour from this red cloth, how am I to accomplish it? I remove it by a very pretty artifice. Chloride of lime bleaches on account of the chlorine that it contains. Now, supposing I desire to get a white place upon this cloth, I have merely to print an acid, such as tartaric acid, upon my red material, and then dip it in chloride of lime. The acid used will unite with the lime and liberate the chlorine, and then a spot will be discharged so that the fabric will be bleached at that spot. I think I can show you this in a simple manner. I have here a solution of chloride of lime, and there are little spots printed on the cloth with tartaric acid. I have here also some Prussian blue printed along with the tartaric acid where the colour will be discharged. Now, if I dip this in chloride of lime and leave it, see how the colour is gradually discharged from the place where the acid was put, producing my white pattern, and at the same time bringing out these beautiful blue spots. This is a topical production of chlorine at the particular place and under the precise circumstances in which we desire to have it. Now, many applications of this principle are made. For instance, I have in this case nitrate of lead and bichromate of potash, which will produce a yellow, and in the same way I can bring out the colour, and produce yellow spots as well as white,-white around the yellow. We can by this means produce a large number of different kinds of patterns, by using my discharger topically, and producing the colours exactly as they are required. Thus, these dischargers, or acids, which are a manufacture of themselves, become an extremely important means of producing various patterns in the calico-printing art.

Now, let us return to the mordants, for they are very important. The mordants are printed on the cloth. Now, these mordants are printed by the machine-acetate of alumina for the red, a dilute solution of acetate of iron for the purple, a strong solution of acetate of iron for the black, and a mixture of acetate of iron and acetate of alumina for chocolate. But all these are soluble, and wash off in water. The object now is to render them insoluble, so that the colour may be lodged within the pores of the cloth itself. That is done by what is termed "the process of ageing." This formerly consisted of hanging up the cloth

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in certain folds in rooms heated to summer temperature, for five or six days, and often for longer, according to the amount of iron which is present in them. During this time, while they are heated up to a summer temperature, the acetic acid escapes from the mordants, and the oxide of iron and oxide of alumina are left upon the cloth. But a large establishment was until recently required for the process of ageing. You required extensive rooms in which to hang up the cloths, and great delay was caused in the dyeing. Within the last year or two an improvement has been introduced, by which the necessity for these extensive rooms is removed. We have only a decade of discoveries to treat of here, between the Exhibitions of 1851 and 1862. In 1856, Mr. Walter Crum, of Glasgow, a man of science, to whom the art of calico printing already owed much of its perfection, discovered a beautiful mode of ageing which is now getting generally adopted. The printed cloths are passed up into a room heated to about 100 degrees, and moistened by steam which comes into the apartment through a trumpet-mouthed opening. By this process the printed material absorbs in fifteen minutes a large quantity of moisture, and it quickly loses acetic acid. It has not, however, become sufficiently aged, and it is therefore now taken from this room and folded up loosely, but simply in single folds. It is put in rooms heated to 80 degrees, and is still kept moist. Here in the course of two or three days it absorbs oxygen and becomes sufficiently aged.

Now comes a curious feature of the operation, which startles one at first as a means of cleansing the cloth. It is necessary, if you will allow me to use the expression, to scour the surface of the cloth in order to make it clean enough for the purpose of the calico printer. You recollect that these mordants have been put on by means of thickeners of gum and various other materials, and it is necessary to remove all these thickeners and other substances by scouring the surface of the cloth, so that the printer can use it. Now, if nothing more than this was required, it would be sufficient to pass this printed material through ordinary hot water, and that would take off the thickeners and leave the cloth in the proper state; but that is not sufficient, and for this reason all the mordants are not decomposed in the process of ageing, Some of them still remain in a soluble state, and if you simply used a bath of hot water the soluble mordants would attach themselves to the portions of the cloth which are to be left white, and would foul them, so that in dyeing, the cloth would be smeared over by the portions of the mordants thus dissolved. To prevent this the calico printer made use of a curious process, which was to pass the cloths through baths in which the dung of cow-houses was placed. In this way all the soluble mordants were converted by the cow refuse into insoluble substances, which could no longer attach themselves to the cloth and cause a confusion of the colours. In consequence of this operation large dairy establishments were connected with print works, so that the printer might have a sufficient quantity of cow refuse for his purpose. After a time, when the action of this substance began to be properly understood, chemists asked themselves whether some substitute could not be used, so that this objectionable process might be dispensed with. They soon discovered that the peculiar action of this refuse upon the mordants was due to the phosphates which it contained to a considerable extent; and it was then easy to make artificial phosphates,-phosphate of soda and phosphate of lime,-and these were mixed together with glue, and sold for a long time under the name of "dung substitute." Within the last few years chemists have found that even these phosphates are not required, and that it is better to use arseniate of soda-arsenic acid united with soda. You may have some idea of the enormous quantity of this highly poisonous salt that is used, when in Lancashire alone 500 tons of this arseniate