DYES 



phenol, naphthalene, and anthra- 

 cene. These are all (except phe- 

 nol) hydrocarbons, i.e. compounds 

 of carbon and hydrogen. Phenol 

 contains oxygen as well, and is 

 commonly called carbolic acid. 

 These substances are the primary 

 raw materials for the production of 

 all artificial dyestuSs. 



Before the actual formation of 

 a dyestuff can take place, the 

 substances mentioned must be 

 converted into what are called in- 

 termediate products, and some- 

 times more than one intermediate 

 takes part in the formation of a 

 dyestuff. The formation of an in- 

 termediate or its practical manu- 

 facture is often more difficult than 

 the actual production of the 

 final dye product, it being fre- 

 quently essential that the inter- 

 mediate should be pure, otherwise 

 the resulting shade of the actual 

 dyestuff is impaired. Sometimes 

 these intermediates are coloured 

 and give coloured solutions, but 

 do not possess the property of 

 dyeing. It will thus be seen that 

 for the actual manufacture of 

 dyestuffs, the production of large 

 quantities of pure intermediates is 

 of primary importance. The for- 

 mation of intermediates from the 

 primary raw materials is carried 

 out by the action of various agents, 

 such as sulphuric acid (oleum), 

 nitric acid, chlorine, bromine, etc., 

 and these processes are called sul- 

 phonation, nitration, chlorination, 

 reduction, etc. 



DYESTUFFS FROM BENZENE 

 Starting from benzene (C 6 H 6 ) by 

 nitration we obtain nitrobenzene ; 

 by reduction, under various con- 

 ditions, this passes into aniline 

 and benzidine. From aniline are 

 obtained, among others, most im- 

 portant basic dyestuffs ; from 

 benzidine by certain other pro- 

 cesses, cotton colours of the direct 

 type are produced. The first cot- 

 ton colour dyeing cotton directly 

 was obtained from benzidine. By 

 introducing chlorine as well as 

 nitric acid into benzene, a com- 

 pound is obtained which forms the 

 raw material for the preparation 

 of the important sulphide blacks. 

 Diagrammatically, the processes 

 may be represented thus : 



Benzene 



I 



obcnz 



Nitrobenzene 

 I 



Aniline 

 Basic Dyes 



Dinitro 

 Cblorobenzena 



Sulphide 

 Blacks 



Benzidine 

 Cotton Dyes 



DYESTUFFS FROM TOLUENE. 

 From toluene by nitration is 

 obtained nitro-toluene (further 

 nitration produces T.N.T. trini- 

 trotoluene, the well-known explo- 

 sive). Nitrotoluene on further 



reduction gives the taluidines and 

 tolidine, both important inter- 

 mediates for direct cotton colours. 

 From toluene also by further re- 

 actions benzaldehyde is obtained, 

 and this is one of the intermediates 

 for both acid and basic colours. 



T.N.T. Nitrotoluene Benzaldehyde 



I 



Tolidine Toluidine 



| | 



Cotton Dyes Acid and Basic 

 Dyes 



DYESTUFFS FROM PHENOL. 

 Phenol on nitration gives nitro- 

 phenols which, further nitrated, 

 give picric acid, and also by com- 

 plicated reactions yield dianisi- 

 dine, the intermediate also valu- 

 able for cotton dyes. Phenol, how- 

 ever, by other suitable treatments, 

 furnishes salicylic acid, which is an 

 important constituent of certain 

 mordant colours, as diamond black 

 and also certain cotton dvestuffs. 



Dianisidinc Picric acid 

 I 



Cotton dyes 



DYESTUFFS FROM NAPHTHALENE. 

 Naphthalene is a most important 

 primary product, and from it, by 

 processes of nitration, reductions, 

 sulphonation, fusion with alkalis, 

 are obtained nitronaphthalene, 

 naphthylamines, naphthols and 

 sulphonic acids of these deriva- 

 tives. The latter possess besides 

 the groups at first introduced, sul- 

 phonic acid groups, which are im- 

 portant constituents, and not only 

 make the resulting dyestuffs more 

 soluble but give them an acid 

 character. These intermediates 

 yield acid dyes, cotton dyes and 

 mordant dyes. 



Naphthalene 



Nitro Naphthalene Naphthalene 



| Sulphonic acids 



Naphthalemine and | 



its Sulphonic acids Naphthols and their 



| Sulphonic acids 

 Acid, direct cotton, and 

 Mordant dye stuffs 



Besides the above dyestuffs, 

 naphthalene forms a source of 

 manufacture of synthetic indigo. 

 By a series of chemical changes, 

 naphthalene is converted into the 

 intermediate phthalic acid, from 

 which are obtained dyestuffs of 

 most brilliant shades such as 

 rhodamine. 



DYESTUFFS FROM ANTHRACENE. 

 Anthracene furnishes the starting 

 point for a large number of most 

 important wool and cotton colours, 

 these being especially important 

 on account of their very good 

 fastness to light, wear, etc. The 



Alizarin and Acid dyestuffs Vat colours 

 other Mordant 

 dyrstuffs 



ACID DYESTUFFS. These are 

 largely used for wool and silk 

 dyeing. Among them are colours 

 which are fugitive to light, also 

 others which are extremely fast to 

 light. Their fastness to other 

 agents, washing, etc., also varies 

 considerably. They are employed 

 for woollen and worsted piece 

 goods, especially for ladies' wear. 



BASIC DYESTUFFS. To this class 

 of colours belong the most brilliant 

 of artificial dyestuffs, which, how- 

 ever, as a class are very fugitive to 

 light. They also possess the ob- 

 jectionable property of rubbing 

 off on to adjacent white material. 

 They find their chief employment 

 in calico printing, also for cotton 

 dyeing for which the cotton has 

 to be previously mordanted with 

 tannic acid and tartar emetic. 

 They can also be dyed on wool. 



Salt dyestuffs are so named 

 because they are used for dyeing 

 cotton from a bath containing 

 common salt. Used in enormous 

 quantities (especially blacks) for 

 this purpose, this group contains 

 colours of every shade, which 

 possess properties of very varying 

 degrees of fastness. Some are 

 very important for union dyeing, 

 as they dye wool equally well from 

 a salt bath. 



Mordant dyestuffs form a class 

 of extreme importance, especially 

 for wool dyeing. Used where great 

 fastness is required, especially to 

 the operation of milling, they prob- 

 ably find their greatest application 

 in loose wool dyeing, but are also 

 employed on pieces, especially for 

 men's wear. On cotton, alizarin 

 is used for the Turkey red process. 



SULPHIDE DYESTUFFS. These 

 colours are only of importance for 

 cotton dyeing, although they can 



DYES 



most striking is alizarin, produced 

 artificially at the same time by 

 Perkin and the German chemists 

 Grabe and Liebermann. Anthra- 

 cene by oxidation gives anthra- 

 quinone which on sulphonation 

 and then a subsequent fusion of 

 the product with caustic alkalis j 

 yields the most important dyestuff, 

 alizarin. Besides alizarin, other ! 

 mordant colours are obtained : 

 from anthraquinone, also very im- 

 portant acid colours such as ali- 

 zarin saphirol. Again, from an- 

 thraquinone the latest series of vat 

 colours are evolved. These vat 

 colours are solely used for cotton 

 dyeing, the vat colours dyeing wool 

 being derived from indigo. 



Anthracene 

 Anthraquinone 



