168 MADDER 



of the colouring-matters wore in a free state, the resinous and yellow colouring-matters 

 would, according to Schunck, unite with the mordants, to the exclusion of the aliza- 

 rine, yielding colours of little permanency and of a disagreeable hue ; but on adding 

 lime, they combine with it, and the alizarine, being less electro-negative, then attaches 

 itself to the mordants or weaker bases. A great excess of lime would of course 

 have an injurious effect by combining also with the alizarine, and preventing it from 

 exerting its tinctorial power. In practice a little less lime is added than is sufficient 

 to take up the whole of the impurities with which the alizarine is associated, thus 

 allowing a portion of the former to go to the mordants, to be subsequently removed 

 by treatment with soap and other detergents. Lastly, it has been asserted by Kochlin 

 and Persoz that when lime is used in dyeing with madder the colours produced are 

 not simply compounds of colouring-matter with mordants, but contain also in chemical 

 combination a certain quantity of lime, which adds very much to their stability. It is 

 probable that all these causes contribute in producing the effect. The carbonates of 

 magnesia and zinc, acetate and neutral phosphate of lime, and the protoxides of lead, 

 zinc and manganese, act in a similar manner to carbonate of lime in madder-dyeing, 

 but are less efficient. 



Dambourney and Beckman have asserted that it is more advantageous to employ 

 the fresh root of madder than that which has been submitted to desiccation, especially 

 by means of stoves. But in its state of freshness its volume becomes troublesome in 

 the dye-bath, and uniform observation seems to prove that it ameliorates by age up 

 to a certain point. Besides, it must be rendered susceptible of keeping and carrying 

 easily. 



In dyeing printed calicoes with madder, the general- course of proceeding is as 

 follows : The madder having been mixed in the dye-vessel with the proper quantity 

 of water, and, if necessary, with chalk, the liquid is heated slowly by means of fire or 

 steam, and the fabric is introduced and kept constantly moving until the dyeing is 

 finished. (See CALICO-PKINTING.) The temperature should be kept low at first, and 

 should be gradually raised, without allowing it to fall, until it reaches the boiling- 

 point ; and the boiling may, if necessary, be continued for a short time. The chief 

 object of the gradual heating seems to be to allow the ferment to exert its full power 

 on the rubian or colour-producing body ; for this process, like all processes of fermen- 

 tation, is most active at a temperature of about 100 Fahr., and is arrested at 212 

 Fahr. In dyeing quickly less permanent colours are also produced, in consequence, 

 probably, of the colouring-matters combining with the more superficial portions of 

 the mordants, and not penetrating sufficiently into the interior of the vegetable fibre. 

 The fastest colours are produced by dyeing at a moderate temperature, and not allow- 

 ing the liquid to boil. By boiling the madder becomes more thoroughly exhausted, 

 and a greater depth of colour is attained, but the latter resists less perfectly the 

 action of soap and other agents, than the same shade dyed at a lower temperature. 

 The time occupied in dyeing varies according to the nature and intensity of the 

 colours to be produced ; but there is little advantage in allowing it in any case to 

 exceed 3 hours, since the gain in coloiir acquired is more than counterbalanced by the 

 loss of time and increased expenditure of fuel caused by a long-continued ebullition. 

 In dyeing ordinary madder colours, such as red, black, chocolate, and common purple, 

 which do not require much treatment after dyeing, in order to give them the desired 

 tone and intensity, strong but inferior qualities of madder may be used with advan- 

 tage ; and various other dye-stuffs, such as peach-wood, quercitron-bark, sumac, &c., 

 are often added to the madder, in order to vary the shade and depth of colour. But 

 for the finer colours, such as pink and fine purple, which after dyeing must be sub- 

 jected to a long course of treatment with soap and acids before they assume the 

 requisite beauty and delicacy of hue, it is necessary to employ the finest qualities of 

 madder; for if dyed with inferior qualities they would resist only imperfectly the 

 requisite after-treatment, and great care must be observed in regulating the tempera- 

 ture during dyeing. The addition of other dye-stuffs, in their case, would be not 

 only useless, but positively injurious. The use of different kinds and qualities of 

 madder in conjunction is often found to be attended with benefit, arising probably 

 from the circumstance of one kind supplying some material or other, such as ferment 

 or carbonate of lime, in which the other is deficient. 



The chemical processes which take place during the operation of dyeing may be 

 shortly described as follow : In the first place, the water of the dye-bath extracts 

 the more soluble constituents of the madder, such as the sugar, extractive matter, and 

 bitter principle. The latter substance is decomposed by the ferment, and the colour- 

 ing-matter thereby formed is added to that which already exists in the root. As the 

 temperature rises the less soluble constituents, such as the alizarine, purpurine, rubia- 

 cine, the resinous colouring-matters, the pectine and pectic acid, begin to dissolve, and 

 as they dissolve they combine partly with the mordants of the fabric, partly with the 



