{ "system": "GoGuides Verified Text", "api_version": "verified-text-v1", "status": "ok", "response_type": "verified_text_record", "source_key": "britannica_1926", "source_title": "Encyclopaedia Britannica (1926)", "license_code": "public_domain", "attribution": null, "license_url": null, "chunk_id": "1926:dyeing:d694b3b9dfb9", "title": "DYEING", "section": null, "hash_alg": "sha256", "hash_sha256": "9cdcb1a73e8bd1dfbeddd4e880d144d7eed5e902e5be70c802cc0a11a5b5c1b8", "normalizer": { "name": "ggnorm", "version": "1.0" }, "verified_text": "profound changes took place between 1910 and 1925, more in the field of industrial politics than in the technical side. i. the industry in great britain war problems—the war produced a period of chaos, and swept the industry into the centre of national politics owing to three main factors—{a) the colour users of the world, of whom textile manufacturers were the most important, had become largely dependent on germany, who, in 1913, supplied three- quarters of the total world demand. switzerland was the second important source, supplying 7%, great britain 6-5%, france 5-4% and the u.s.a. 3-3°%. (8) on the outbreak of the war the nations of the world suddenly found their supplies cut off, and the important textile industries of great britain, france, italy and the united states were in a most difficult position. (c) in addition, colour-chemistry produces a number of chemical e€xperts, whose knowledge enables them to apply chemicals to war purposes in the production of high explosives, such as picric acid and t.n.t., and also in the manufacture of poison gas and the like. it is true to some extent that dye factories can be used for the making of high explosives, but what is more important is that this industry provides a reserve of highly qualified chemists whose services the govern- ment can, if necessary, utilise for war purposes. thus the nations at war with germany found their national wellbeing threatened at two points: firstly, a whole group of basic in- dustries, the textile, were jeopardised; while, secondly, the nationa) existence itself was threatened by the superior skill of their opponents in chemical warfare (q.2.). the various nations met the crisis in different ways, according to the national temperaments. in great britain, at the out- break of war, there existed five important british firms making dyes and two german firms with works in great britain. the latter were sequestrated by the british govt., and ultimately disposed of to british firms. the output of the british firms, even when supplemented by supplies from switzerland, was totally inadequate to meet the requirements of the british textile manufacturers, on whom the demand was abnormally increased by the government requirements for military and naval uniforms and the like. the average annual british import of dyes from abroad in pre-war years had amounted to nearly 18,000 tons, worth £2,000,000. many important dyes, such as synthetic indigo, were german trade secrets and had never been made in this country. british dyes ltd.—to mect these difficulties the government, in close co-operation with the users of dyes, established a com- pany named “ british dyes ltd.,” with a capital of £3,000,000, of which the government supplied half. the new firm started by taking over one of the old works, that of messrs. read, holliday & co., at huddersfield, but began to build new and enlarged works. the building went on during a period of con- tinuously rising prices, and ullimately the huge size and enhanced cost of these buildings became a scrious liability to the firm, or rather to its successor. meanwhile other works sprang into existence, encouraged by the large profits which for the time being were obtainable. during this period the chicf difficulty was that of working out the formulae for the intermediate products, especially for the azo dyes, nearly all of which had previously come from ger- many. in addition, british dye manufacturers found themselves faced with a shortage of certain needs, especially “ oleum ” and oil of vitriol, which necessitated the construction of new chambers and contact plant. 885 government action after the war.—considerable progress was made, however, and at the conclusion of the war the govern- ment recognised that the dyestuffs industry must be protected and helped to establish itself on a sufficiently firm basis to prevent the recurrence of such a crisis. it therefore recognised the production of dyes as a key industry, and extended to it a strong measure of protection against foreign competition; and secondly, it helped in the establishment of a new firm, which absorbed not only “ british dyes lid.” but also its chief com- petitor, levinstcin ltd., who had previously bought up another important firm, messrs. claus & co. during and immediately after the war the government had restricted the importation of german dyes by proclamation; but when peace had been signed this procedure was challenged, and in a test case the courts decided that the proclamation was iwegal. in consequence, a special act of parliament, the dye- stuffs (import regulation) act 1920, roand 11 geo. v., cap. 77, was passed, which came into force jan. 15 1921. this act is intended to protect the dye industry for 10 years, and under it no dyestuff may be imported which can be satisfactorily made in great britain, while, where imports are shown to be neces- sary, a licence must be obtained from a committee appointed by the board of trade. thus the new firm, “‘ the british dyestuffs corporation ltd.,” practically constituted a monopoly, and in order to safeguard national industries in general, and particularly those of dye users, the government insisted on retaining considerable control in the administration of the business. the shareholders of british dyes and of levinstein ltd. exchanged the holdings they had in these concerns for shares in the new company. the government, in lieu of the amount it had technically “loaned ” to british dyes, received {1,700,000 worth of shares, and subscriptions were invited for {£5,0co,ooo new capital. these were taken up by the general public, mostly by people not interested in the business as colour users, thus creating an entirely different situation, for the new firm, the british dye- stuffs corporation ltd., had now to earn dividends to satisfy these shareholders, whereas “ british dyes ” might have been able to satisfy its shareholders, the dye users, if it provided good and cheap dyes, even if its profits were negligible. the british dyestuffs corporation had therefore to satisfy its share- holders like any other business, while its hands were, to a con- siderable extent, tied by the governmental control to which it had to submit, and the objects of the government were obviously not precisely the same as those of the people who had subscribed money in the expectation of receiving good dividends. the clauses in the articles of association which placed the government in a peculiar position were three in number :— (a) the allotment to government nominees of a special share carrying special voting rights for the purpose of preventing any alteration in the company's articles of association. (6) restrictions on the allotment and transfer of shares to foreign- ers or persons under foreign control, and provisions under which it was necessary to secure the consent of the board of trade to any allotment or transfer of shares to such persons. (c) the nomination of two directors by the government, and the exercise by those directors of certain powers of veto and control over the company’s affairs. the nominal share capital of this new venture was fixed at £10,000, 000. reconstruction.—it was hoped by these two measures to estab- lish the manufacture of dyes in great britain on a firm basis; but by 1925 it had been found that although the licensing system worked fairly smoothly, despite a certain amount of complaint from the colour users, the british dyestuffs corpora- tion itself was not a financial success. on nov. 25 1925 it was reconstructed, the issued share capital of £9,197,112 was reduced to £4,775,000 and the articles amended. the government abandoned all claims to control the com- pany and surrendered its shares, which then amounted to {1,700,000, for a cash payment of f600,000. the company agreed to keep in touch with the board of trade in all matters of technical information and research, and also undertook that 886 not more than 25% of its shares should be held by foreigners. the partial failure of the corporation was largely caused by two other factors, firstly the cost of its vast new works at hudders- field, built at a time of inflated prices; and, secondly, a changed economic situation. all other nations had established dycstuft factories of their own, and in 1925, while the output of the world was four times that of 1913, effective demand had not kept pace with this expansion, and there was not enough business to meet the overhead charges of all. (j. s. ml. w,) ii. the industry in the united states the dyeing industry of the united states during the period i9g1o-26 grew commensurately with the textile industries. an important advance was made in the production of fast col- ours, especially on cotton goods. this was in keeping with the rapidly extended use of cotton in high-grade wearing apparel and with the increase of steam laundries, displacing household washing. modern laundry methods or rapidly cleansing and whitening fabrics necessitated the use of strong chemicals, destructive of many of the colours formerly employed in dyeing cotton. the demand for laundry-fast colours was met by the introduction of the so-called “‘ vat ’ dyes, of which indigo was long the only representative. the extended use of the dye known as sulphur black to take the place of aniline black for cotton hosiery and ptece-goods was also worthy of note. the silk in- dustry also grew largely, the united states consuming more raw silk in manufactures than any other country. this led to the great extension of silk-dyeing, chiefly in the industrial centres of south manchester, conn., paterson, n.j., and lancaster, penn- sylvania. another branch of the textile industry which has developed to great proportions in the period 1920-6 is that of artificial silk or rayon fibre. this has required a corresponding development in the dyeing industry, as this new fibre requires special methods of dyeing, and in some cases new kinds of dye- stufis. at the present day there is even a larger amount of rayon fibre manufactured than there is of natural silk, and the industry is still growing rapidly. | the world war at first threw the dyeing industry in the united states into confusion, owing to the uncertainty of trade relations with germany, the more so when the allied blockade put a complete embargo on germany’s exports. it was then seen how dependent america had been on germany for dyestuffs, and it was estimated that manufacturing industries with products valued at about $4,000,000,000 might soon be thrown completely out of gear by a lack of dyestuffs. in the confusion which resulted many expedients were adopted in the production of colours, with a consequent reduction in the fastness and quality of dyeing. dyestutfs became so scarce that exorbitant prices stimulated the erection of many dyestuff factories in various parts of the united states. large amounts of capital were freely invested in the new industry, and many chemists became engaged in dyestufi research and manuiacturing. previous to the war the united states had a small dyestuff industry distributed among about five plants. the manufactur- ing operations, however, were limited chiefly to the assembling of the coal-tar intermediates imported from germany for the production of the finished dyes, so that the new industry had to be built from the ground up. to the great creclit of the american chemist and chemical manufacturer it may be said that in a very short time the more important dyes were successfully made in the united states in such quantity that practically no dye-con- suming industry was forced to shut down by reason of a lack of dyes. in 1924 there were 193 firms in the united states engaged in the manufacture of coal-tar chemicals, and of these 78 firms were engaged particularly in the making of dyestuffs, producing 68,679,000 |b. of the various synthetic dyes. of the dyes sold to consumers the value was $35,012,400, at an average price of 54c per pound. of the total dyes consumed in the united states about 96°% were produced by the domestic industry and only about 4°% were imported dyestuffs, the latter coming chiefly from germany and switzerland. about 20,000,000 ib. of synthetic indigo were produced in the united states in 1924, about twice dyeing the pre-war importation, indicating a great extension in the use of indigo in dyeing. sulphur black was also produced on a very large scale, as well as all of the required acid dyes for wool and silk, most of the basic dyes, a complcte line of direct cotton dyes, and what was still more significant, a rather complete line of vat dyes as well as alizarine and mordant dyes for the fast colours. associated with the making of dyestuffs there also grew up the many related branches of the coal-tar chemical industry, such as colour-lakes for paints; lithographic and printing inks; coal-tar pharmaceuticals; flavouring and perfume materials; photo- graphic chemicals; and synthetic tannins and resins. the great growth of the industry created a constant demand for increasing quantities of coal-tar distillates, which form the raw materials of the dyestuff industry, and this led to a rapid increase in the num- ber of by-product coke ovens. in 1924 the production of coke in by-product ovens amounted to nearly 78% of the total. the great production of dyes in the united states during the post-war period led to the building up of a considerable export trade, particularly to south america and the orient. the total dyes exported from the united states in the year 1924 amounted to 15,713,428 lb., with a value of $5,636,244. the dyes exported, in fact, were about five times the amount and about twice the value of those imported. the dyestuft industry in the united states was wisely protected and fostered by the government by suitable tariff and licensing regulations during the post-war period and has now been established on a firm and permanent basis, and this has greatly aided the stability and prosperity of the dyeing industry. in the matter of natural dyestuffs america has always occupied a leading position. many of the principal natural dyes are of american origin. logwood, fustic, cochineal and the red-woods are all american products, discovered in and still obtained from mexico, central america and south america, as well as the west indies. during the war a product very closcly resembling fustic and known as osage orange was developed in the united states and was produced and consumed in large quantities. as the dyer at the present time usually employs the colouring matters of the dyewoods in the form of suitable extracts, there has long been developed in the united states a considerable industry in the manufacture of these extracts, generally produced in connection with the manufacture of tannin extracts. this industry is in no way associated with the coal-tar dyestuff business. the scarcity of dyes during the early part of the war resulted in a great expansion of the dyewood extract industry, which, however, rapidly declined as the manufacture of synthetic coal- tar dyes increased. in former years natural indigo was exten- sively used in dyeing, and in early colonial days, large quantities of this dye were cultivated in the southern states. as the growing of cotton increased, that of indigo was neglected, so that most of the indigo used in the united states was imported, chictly from the far east. the advent of synthetic indigo, however, soon displaced the natural product, so that but very little of this vege- table dye is now used in america. with the exception of log- wood, which is still employed in considerable amounts for the dyeing of silk and leather, the use of the natural dyewoods is fast decreasing. in the dyeing of woollen matcrials the use of logwood has been displaced by coal-tar dyes that give better and faster colours. contrary to the belief of many unacquainted with the facts, the natural vegetable dyeing materials can in no wise equal in fastness and in purity of colour many of the recently introduced fast coal-tar dyestuffs comprised among the so-called “vat”? dyes for cotton and silk, the alizarine and chrome dyeing colours for wool, and the naphthol coupled colours for cotton dycing and calico printing. it is now possible to produce coloured fabrics which will stand sun and climatic exposure as well as bleaching and severe laundering in a manner a great dea) better than could be obtained with the old-fashioned vegetable dyes. this has iced to many innovations in the application of dyestuffs, and many new processes of dyeing have been devised that have greatly enlarged and enriched the art. another recent devclop- ment in the dyeing industry in the united states is that of fur dyeing. during the post-war period, owing to the shifting of dyling the centres of trade, the united states became an important market for the sale and manufacture of furs. this has resulted in the building up of an extensive industry in the dyeing and finishing of furs, which will without doubt become firmly estab- lished as an important adjunct to the general dyeing industry of the united states. (j. m. m.*) iii. the industry in germany and switzerland germany.—in germany the industry was firmly established before the war, but it was confined to three main groups which during the war came together under a working agreement and pooling arrangement. in 1925 a financial amalgamation gave the new farben industrie interessen-gemeinschaft, or ‘‘ i.g.” as it is known, capital resources of about {40,000,000. the 1.g., which is interested not only in actual dyestuff manufacture but in heavy chemical production, and also in making fine chemicals for pharmaceutical, medicinal, photographic, etc., purposes, still holds the premier position in the world’s dyestuff trade; but the dominant and almost monopolistic position it held before the war has gone, chiefly through the loss of its former british and american markets and the increase of com- petition in the principal free dye markets of the world—india and china. the output of the german factories was intluenced consid- erably during the few years following the armistice by the fact that they were situated for the most part in the occupied areas, and consequently were under the control of the allied army. in 1919 a military commission of inspection representing the different allied countries visited the factories, and though their report was never published the commission indicated quite clearly that the resources of the german dye industry had been directed almost solely to the prosecution of the war, and had contributed in no mean degree to the extent and duration of the resistance which germany had been able to offer. definite connections were established between the dye factories and poison gas manufacture. during the peace treaty negotiations there was a fear that germany might endeavour to make use of her position in the chemical and dyestuffs industry to secure special terms, or alternatively that, by withholding supplies of such chemical products including dyes as were only available from germany, attempt to hinder the economic recovery of the allied countrics during the period of reconstruction. clauses were therefore inserted in the treaty of versailles (annex 6 to part viii.) whercby an option was accorded to the reparation commission on one-half of the stocks of dyestufls and chemical drugs in germany at the time, and also on 25% of the german output of these products for a period of five years from jan. 1920. this period was subsequently extended by the london agree- ment of aug. 30 1924 to aug. 28 1928. under these arrange- ments large quantities both of dyes and drugs have been delivered by germany on reparation account and, but for a temporary dislocation during the occupation of the ruhr by the i'rench, the arrangements laid down by the treaty have worked satisfactorily and smoothly. some difficulty has, how- ever, been occasioned, particularly to dye manufacturers, be- cause certain countries requisitioned quantitics in excess of their domestic requirements and re-exported these excess quantities at uneconomic prices. france, italy, japan, spain.—in france a national dye fac- tory was started with government assistance, and the pre-war factories in france belonging to the german dye firms were taken over and developed by french concerns. nevertheless, france is still dependent on foreign sources for the supply of about one-half of her requirements of dyes. the same is the case with italy; whilst as regards japan an attempt to create a national dye-making industry with a large measure of govern- ment financial assistance has not met with any marked success. in spain a system of control of imports has been adopted, presumably with the object of protecting the one or two small dye-making factories in that country. 887 switzerland.—the four factories which were in existence in switzerland before the war have made considerable progress since that time. whilst competition from germany was sus- pended owing to the war the swiss factories made large profits which enabled them to modernise and extend their works and to write off their plants. they made an arrangement with the british govt. in 1915 whereby in return for supplies of raw materials and intermediates they supplied the british market with a large proportion of their output. as the swiss factories are situated at basle, close to the german frontier, and most of the materials supplied to them were of immense importance for war purposes, a system of control by british officials of the swiss factories was instituted during the war period, but at no time was there any evidence of the misuse by the swiss of the materials sent to them, they being most anxious to fulfil their arrangement with great britain not only to the letter but in the spirit. since the war one of the swiss firms—-durand huguenin, s.a.—has been acquired by the german i.g., whilst the other three have formed a “ community of interest,’’ under which they are working together by means of a pooling arrange- ment for a period of 50 years. these three swiss firms jointly own a factory in england—the clayton aniline co. ltd., manchester—which has made great progress, especially in manufacturing a number of dyes formerly imported from switzerland. whether the clayton factory would continue to be developed to the same extent under a system of free impor- tation into england is open to some doubt. the capacity for the production of dyestufis throughout the world has increased enormously since the war, but it is doubtful if there has been any appreciable increase in the rate of con- sumption during this period. this excess of capacity over de- mand prevents manufacturers from producing dyes under the most efficient conditions, and in certain cases, as in the u.s.a,, this has resulted in price-cutting campaigns. in others, as for example germany, the efforts of the dye-makers have been directed to other and more remunerative channels, such as the development of products based on synthetic nitrogen and syn- thetic methyl alcohol. the experience of the war years has shown quite definitely that no country can, without grave risk to its national security and economic prosperity, allow itself to become dependent solely on foreign sources for its supply of dyestufis and kindred products. cw. gr.*) bibliography.— memorandum by the board of trade on the scheme for the allocation by parliament for the development of the dye industry, etc., cd. 9, 194 (1918); dyestuffs uimiport regulations) act 1920, chap. 77; report from standing committee b on the dye- stuffs (import regulation) bill (242) 1920; british dyestuffs corpora- tion lid., papers relative to the liquidation of the government in- terests in the british dyestuffs corporation lid., cd. 2545 (1925). iv. technical advances since 1910 important advances in the application of dyes to fabrics from the scientific aspect since 1910 have been mainly concerned with a simplification of the dyeing process, and the production on the fibre of shades of extreme fastness. experience now enables us to predict with some certainty how a dyestuff of known chemical constitution can be applied to this or that fibre, but, on the other hand, there is still no general agreement as to what hap- pens as the result of the dyeing operation. thus the artificial dyestuffs are classified for tinctorial purposes, by possessing certain special chemical groupings, rather than by their more exact structure, for these groupings determine their attraction for this or that fibre and as a consequence their mcthod of appli- cation thereto. new dyestuffs of importance have been discovered, and with few exceptions, they require no special dyeing processes. as a result the main principles of this art have remained unaltered. the advent in to2t of the so-called celanese silk (partially acetylated cellulose) provided the world with a fibre of distinct properties, for the dyeing of which, however, new methods and colouring matters have in part been found essential. sulphide dyestuffs —with regard to the employment of these colouring matters for the dyeing of cotton, their chief function, 883 there is little new to be said. the dyeing process consists essen- tially in converting the insoluble colouring matter by means of sodium sulphide into the soluble sodium salt of its leuco-com- pound. this possesses an affinity for the cotton fibre, and by air oxidation passes thereon into the insoluble dyestuff. the defect, that such dyed material, on keeping, is liable to be- come tender owing to a development of sulphuric acid, has been carefully studied, and it is now known that the formation of this acid is due not to the presence of sulphur in the free condition, but to an oxidation of a part of the sulphur which jis in actual com- bination with the dye itself (w. zanker, farber zeitung, 1914). trouble due to this character is now rarely experienced. though the sulphide dyestuffs are largely in use for cotton dyeing, their application to wool in a satisfactory manner was hardly feasible, because sodium sulphide is strongly alkaline, and readily attacks wool. this difficulty can be overcome by the lodge evans process (jour. soc. dyers and colourists, p. 252, 1918), based on the fact that sulphide dyestuffs are soluble in sodium sulphite solution. these solutions, however, are devoid of dyeing property because the colouring matter is not present therein as leuco-compound; but on adding sodium hydrosulphite or ammonium sulphide this change occurs and the bath is now ready for use. this process, which is of value for dyeing union material solid shades of black, is not of importance for all wool material, because other fast colours, more easily applied, are available for this purpose. insoluble aso dyestuffs —the method for the application of these insoluble colouring matters to cotton consists in the actual formation by chemical means of the dyestufi on the fibre. thus the material padded with the solution of one of the components of the reaction, generally the sodium salt of beta-naphthol, is dried, and then passed into a bath of the second component, invariably the salt of a diazotised aromatic base. reaction occurs almost instantaneously with formation of the azo colouring matter, and by employing the diazo compounds of different aromatic bases varied shades can be obtained by this process. the dyeing of cotton yarn and calico by this method is extensively practised, because these colours have good fastness to soap, and are fairly fast to light. the diazo compounds of these bases are of an unstable char- acter, and are thus prepared (in solution) shortly before use, (and preferably cooled by ice). it was, however, shown in 1894 that by simple methods these may be converted into stable inactive forms, which are now on the market, and can quickly be rendered ready for use as occasion requires (colour index, no. 44). the application of beta-naphthol as sodium salt to cotton, for which it has no affinity, requires extreme care, for in case the dried material is not evenly impregnated therewith, the finished shade will be uneven. in 1912 a substitute for beta-naphthol was placed on the market by the chemische fabrik griesheim electron, and this, known as naphthol a.s., is the anilide of beta- hydroxy-naphthoic acid (colour index, page 333). as sodium salt, it possesses a distinct affinity for the cotton fibre, and the treated material can thus be at once immersed in the diazo solution without previously drying. the shades thus produced are both brilliant and fast, and, though more costly, it is much superior to beta-naphthol for this purpose. again, in 1916 a further simplification of the proc- ess was announced and products known as “ rapid fast dyes ” came on to the market. these consist of one or other of the stable diazo compound preparations referred to above, admixed with naphthol a.s. (colour index, page 364), and by merely padding the cotton in a solution of such a product, drying and steeping in a bath of hot dilute acetic acid, the colour is at once developed. certain of the insoluble azo dyes (such as para red, which has been much used as a cheap substitute for turkey red), on account of their chemical nature, are capable, when dyed on cotton, of withstanding to some extent a mild bleaching operation, that is to say, a moderate kier boiling of the material with dilute alkali, and subsequent treatment with bleaching powder solution. thus yarn dyed therewith can be interwoven with unbleached white cotton in the form of stripes and fancy patterns, and the goods dyling subsequently bleached. for this type of process, which is much in vogue, the ordinary insoluble azo colours are markedly in- ferior to turkey red, indigo, the vat and certain other dyes, but since 1921, faster members of this class have been prepared. these, which can be produced on the fibre according to the meth- ods given above, are obtained by employing on the one hand new derivatives of beta-hydroxy-naphthoic acid anilide, and on the other of diazotised bases generally of a more complex character than,those formerly in use. much which is claimed for these new colours is correct, and the progress of their technical application both in dyeing and calico printing will be awaited with interest artificial silks —the so-called “ artificial silks ” (g.v.) which have come into increasing prominence during recent years are all obtained from cotton, wood-pulp or some other form of cellu- lose (q.v.), and until recently all the varieties on the market con- sisted in their essence of cellulose itself. the processes applicable for dyeing these materials are gen- erally identical with those available for cotton, though owing to their more fragile nature and a liability for the production of uneven shades, the operation requires special care. shortly after the conclusion of the war, a new variety, known as “acetyl silk ” or “ celanese silk,” came on to the market, which differs in a very interesting manner from other artificial silks in regard to its affinity for dyestuffs. it consists of cotton which has been partially acetylated by means of acetic anhydride, and thus contains acetyl groups which render it more acidic than cotton itself. as a result, it possesses, especially in the presence of certain inorganic salts, a marked attraction for basic dyestuffs, a group of colouring matters to which cotton is practically inert, but on the other hand has littie or no affinity for the direct cotton colouring matters. the most important of the methods proposed to overcome this latter difficulty at the time was a conversion of the surface of the fibre into cellulose by the hydrolysing action of alkali (g. i*. briggs, jozr. soc. dycrs and colourists, p. 287, 1921). when cautiously treated in this manner, the lustre of the silk was not specially impaired but among other difficulties a loss in weight and in strength is liable to occur. a second method is the use of ammonium thiocyanate (l. g. lawrie, tbid., vol. ii, p. 69, 1924), which renders the celanese silk capable of dyeing with cotton colouring matters. much more valuable has been the discovery of dyestuffs and dye prepara- tions especially adapted to the peculiarities of this fibre. acetyl silk possesses an attraction for insoluble colouring mat- ters, generally of a basic character, in case these are in a highly dispersed or colloidal condition (g. h. ellis, zbid., p. 285, 1924) and the so-called sulpho-ricinoleic acid colours are, at least in part, solutions of simple amino-azo compounds in sulpho- ricinoleic acid. the duranol, dispersol and celatene colours again are dye preparations of a similar type (lawrie, /oc. cit.). the dyeing of the acetyl silk with these colours merely consists in immersion of the material in the dyebath at a temperature not exceeding 80°c, ‘ the ionamines of a. g. green and k. h. saunders (jour. soc. dyers and colourists, p. 10, 1923; p. 138, 1924), in their essence consist of insoluble basic compounds rendered soluble by a chemical addition of the (ch2oh-so3h) group. these (omega sulphonic acid) compounds, though zomparatively stable in neutral solution, are readily converted (hydrolysed) by acids and alkalis with regeneration of the insoluble colouring matter, a reaction which accounts for their behaviour as dyestuffs. thus in the dyeing operation, which is carried out at 65-75°c. in the presence of a little formic or sulphuric acid, the soluble ionamine, at first attracted by the acetate silk, is there decomposed, with deposition of the colouring matter on and in the fibre. the dyed colouring matters are basic, that is, contain a free amino group, and by diazotisation and coupling in the usual manner with a phenolic developer, such as beta-naphthol, beta-naphthoic acid anilide (naphthol a.s.) or resorcin, various shades can be obtained. ‘for a detailed description of these compounds, the papers of f.m. rowe and e. levin (jour. soc. dyers and colourists, p. 204, 1921, and pp. 218, 230, 1924) should be consulted. dynamo-electric machines though acetyl silk has little affinity for soluble dyes of the sulphonic acid class, the british dyestuffs corporation, ltd. (british pat. 202,157, 1922), discovered that amino-azo and other insoluble basic dyes, on conversion into carboxylic acids, give soluble products suitable for dyeing acctate silk, and that these again can be converted into a new dye on the fibre by the diazotisation and coupling process. excellent shades of indigo blue can be dyed on acetyl silk by employing a vat containing a solution of indigo white, sodium hydrosulphite and ammonia together with a little glue. there is no real difficulty in dyeing mixtures of acetyl! silk and cotton, as two distinct colours can be employed in the same bath, each having an affinity for one or other of these fibres. with mixtures of wool and acetyl silk the difficulties are greater, but by first dyeing the latter with a colloidal dye preparation, and subse- quently the wool with suitable acid dyestuff, these can be avoided. the cotton material known as “ immunised cotton,” altered by the action of sulphonic chlorides (sandoz, basle) (g. tagliani, jour. soc. dyers and colourists, p. 163, 1925), resembles acetyl silk in dyeing property, in that it has no attraction for direct cotton colours, though a great affinity for basic dyes. as this ‘immunisation ” of cotton can be carried out locally on either yarn or piece goods, many varied colour contrasts can be ob- tained by its use both in dyeing and calico printing. vat dyes.—this group contains, in addition to indigo and its derivatives, numerous colours derived from anthraquinone, among which are the fastest dyes known. the use of many of these latter has until recently been mainly confined to cotton, because their usual method of application entails an amount of alkali in the dyebath (vat) which is injurious to wool. wool, again, according to h. kammerer (jour. soc. dyers and colour- ists, p. 68, 1913), shows much less affinity for these colouring matters as leuco-compounds than cotton, and dyeing as a rule with this fibre does not commence below 70° centigrade. em- ployment of the minimum of alkali, and the addition also of glue to the vat hinders the injurious action of the alkali on the wool, and satisfactory resulis are thus possible. a new method for the application of vat dyes to acetyl silk in admixture with cotton (british celanese co.) consists in replacing the harmful alkali of the hydrosulphite vat by sodium phenate (carbolate) and is more specially applicable to those colours which require but small amounts of alkali in the dycing process. the vat may be set in the usual manner with alkali, and the excess of the latter may be neutralised with phenol (carbolic acid). indigo is prepared by the colourmakers in an easily soluble reduced form, and similar preparations of certain other of these vat dyes are on the market. these termed “ anthre dyestuffs ” are recommended as serviceable for wool dyeing, employing in the vat sodium hydrosulphite, ammonia and glue solution. for protecting wool from the action of the alkali (actien g. f, anilin- fabrikation) sulphite cellulose liquor, obtained in the manufacture of wood-pulp, is recommended, and a preparation termed “ pro-~- tectol,” probably contains this (a. exge, jour. soc. dyers and colourists, vol. 38, p. 136, 1922). according to kollmann (jour, textile institute, vol. 13, p. 16, 1922), vat colours can be dyed on wool from a bath containing hydrosulphite of soda and ground chalk or zinc oxide. ‘‘ indigosol’’ (colour index no. 1178) is a product prepared from indigo, which by acid oxidation is readily reconverted into this colouring matter (hlugenin) (jour. sec. dyers and colourtsts, p. 340, 1925). this, which is a sodium compound of the disulphonic ester of indigo white, is readily soluble in water and thus can be used for the dyeing or printing of indigo on cotton, wool or silk. woollen goods may be immersed in a bath of indigosol containing sodium sulphate, together with a little acetic and formic acids. after washing, the blue is developed by steeping the material in dilute nitrous acid (sodium nitrite and dilute sulphuric acid) (durand and hugenin). cotton can be dyed by a similar process, em- ploying in the same way a mild oxidising agent, such as ferric chloride, acidified bichromate or nitrous acid. another product of a similar type, “ soledon jade green,” derived from an anthraquinone vat dyestuli (scottish dyes, s8q ltd.}, can be applied to fabrics in a similar way to indigosol. other anthraquinone dyestulls of this type have been prepared, and a new process is thus now available for the use of these fast dyes on wool and silk, simple in its application, and avoiding the harmful use of alkali in the dyebath. basic colours.—as these dyes possess little or no affinity for cotton, a tannin antimony, lake or mordant is usually first pre- cipitated on the fibre by steeping the undyed material in a tannin solution and then in a bath of tartar emetic. new so-called mor- dants for this purpose (bayer & co.) consist of phenolic com- pounds containing sulphur and a preparation of this kind, termed “ katanol o,” is on the market (colour index, 357 (jour. soc. chen. dnd. 136a, 1922). the operation of mordanting cotton with this preparation is much simpler than by the tannin method, and again the shades obtained are purer and of greater fastness to washing. the cotton is merely immersed in an alkaline solution of the katanol con- taining common salt, and after rinsing is ready for the dyeing operation (see also r. fischer, textile berichic, p. 119, 1924). a second preparation, termed “‘ katanol w,” removes the affinity of the animal fibres for certain of the direct cotton colours. by its use in the case of mixed fabrics the cotton may be dyed a full shade, whereas the animal fibre remains unaffected. mordant dyes yield coloured lakes with metallic oxides. the method of first mordanting the material and dyeing in a sepa- rate bath is still in vogue with certain of the phenolic dyestuffs, such as the alizarines, logwood, etc. the more simple procedure of mordanting during the dyeing operation, or at its close, in the same bath, with copper or chromium salts, employing acid mor- dant dyes largely of the azo class, is now far more gencrally em- ployed. in addition to the older mordants employed in this one bath method, chromium oxalate or ‘“ chromosul”’ mordant (sandoz) finds some service. the dycing operation is again sim- plified by the use of colouring matters soluble in water and con- taining copper or chromium in combination, which, in the dyeing or printing operation, are fixed on the fibre as insoluble metallic lakes, such as the neolan colours (society of chemical industry, basle) (i. whitworth, jour. soc. dyers and colourists, vol. 40, p. 256, 1924), which are applied in the presence of sulphuric acid. the chemical nature of the lakes contained by the combina- tion of dyes with metallic mordants has been investigated from the point of view of the co-ordination theory of valency by g. t. morgan and his pupils (see jour. soc. dyers and coleourists, vol. 37, p. 43, 1921). | theories of dveing—numerous theories have been proposed in the past to explain the dyeing operation, namely, the “ mechanical,” “solid solution,” ‘‘ absorption,” ‘‘ colloidal” and ‘‘ electrical ”’ theorics, the latter being of the most recent date. in regard to these theories of the dyeing process, it begins to be clear, as w. ostwald himself indicated (oxilines of general chemistry, p. 295, 1912), that no single theory can account for all dyeing proc- esses. in any case, it seems probable that two stages occur, the first being due, it may be, to either adsorption or electrical attrac- tion. this is then followed by fixation of the dye in or on the fibre by solid solution, colloid aggregation, or by chemical interaction, and these may come into play according to the nature of the fibre, the process and the character of the dyestuff involved. brpryograrny.—e. knecht, c. rawson and r. loewenthal, manual of dycing (1910); j. lliibner, the bleaching and dyeing of fegetable fibrous materials (1912); h. t. bucherer, lehrbuch der farbenchemte (1914); c. m. whittaker, the application of ihe coal tar dyestuffs (1918); j. m. matthews, application of dyestuffs (1920); f. a. mason, g. o. georgievics and e. grandmougin, a text book of dye chemistry (1921); e. knecht and j. b. fothergill, the principles and practice of textile printing, 2nd j-d. (1924); 5s. r. & fe. r. trotman, the bleaching, dyeing and chemical technology of textile fibres (1925). (awge pi) dynamo-electric machines (sce 8.764).—-the term