MADDER 



165 



which should remain white are found to have a yellowish colour. Hence it is of im- 

 portance to the dyer that their effect should be counteracted as much as possible, by 

 preventing them either from dissolving in the dye-bath or from attaching themselves 

 to the fabric. 



The other constituents of madder possess no interest in themselves, but may be- 

 come of importance in consequence of the effects which they produce during the pro- 

 cess of dyeing. The pectine, in the state in which it exists in the root, is probably 

 an indifferent substance, but in consequence of the ease and rapidity with which it 

 passes into pectie acid, it may in dyeing act very prejudicially by combining 

 with the mordants and preventing them taking up colouring matter. The extrac- 

 tive matter of madder, when in an unaltered state, produces no injurious effects 

 directly ; but by (he action of oxygen, especially at an elevated temperature, it ac- 

 quires a brown colour and then contributes, together with the rubiacine and the 

 resinous colouring matter, in deteriorating the colours and sullying the white parts 

 of the fabric. The extractive matter, when in a state of purity, has the appearance 

 of a yellow syrup like honey, which is easily soluble in water and alcohol. When 

 pure it is not precipitated from its watery solution by an earthy or metallic salt, 

 but if the solution be evaporated in contact with the air, it gradually becomes brown, 

 and then gives an abundant brown precipitate with sugar of lead. When its watery 

 solution is mixed with muriatic or sulphuric acid and boiled, it becomes green and 

 deposits a dark green powder. Hence this extractive matter has, for the sake of dis- 

 tinction, been called Chlorogenine, and Rubickloric Acid. The bitter principle of madder 

 will be referred to presently. The Xanthine of Kuhlmann, and the madder-yellow of 

 Runge are mixtures of the extractive matter and the bitter principle. The sugar 

 contained in madder is probably grape-sugar. It has not hitherto been obtained in a 

 crystallised state, but it yields by fermentation alcohol and carbonic acid, like ordi- 

 nary sugar. The woody fibre which is left after madder has been treated with 

 various solvents until nothing more is extracted, always retain a slight reddish or 

 brownish tinge from the presence of some colouring matter which cannot be com- 

 pletely removed, and seems to adhere to it in the same way as it does to the cotton 

 fibre of unmordanted calico. 



There is a question connected with the chemical history of madder which must not 

 be passed over in silence, since it is one which possesses great interest, and may at 

 some future time become of great importance, viz. the question as to the state in which 

 the colouring matters originally exist in the root. It has long been known, that when 

 ground madder is kept tightly packed in casks f&r some time, it constantly improves 

 in quality for several years, after which it again deteriorates ; and it was always sup- 

 posed that this effect was due to some process of slow fermentation going on in the 

 interior of the mass, an opinion which seemed to be justified by the evident increase 

 in weight and volume, and the agglomeration of the particles which took place at the 

 same time. Nevertheless, the earlier chemical examinations of madder threw no light 

 whatever on this part of the subject, since the red colouring matters were found to 

 be very stable compounds, not easily decomposed except by the action of very potent 

 agents, so that when once formed it seemed improbable that they would be at at all 

 affected by any mere process of fermentation. Hence some chemists were led to the 

 conclusion that the improvement which takes place in the quality of madder on keep- 

 ing is caused by an actual formation of fresh colouring matter. A very simple ex- 

 periment may indeed suffice to prove that the whole of the colouring matter does not 

 exist ready formed, even in the article as used by the dyer. If ordinary madder be 

 extracted with cold water, the extract after being filtered has generally an acid re- 

 action, and cannot contain any of the colouring matters, since these are almost in- 

 soluble in cold water, especially when there is any acid present. Nevertheless the 

 extract when gradually heated is found capable of dyeing in the same way as madder 

 itself. If the extract be made tolerably strong, it possesses a deep yellow colour and 

 a very bitter taste ; but if it be allowed to stand in a warm place for a few hours, 

 it gelatinises, and the insoluble jelly which is formed is found to possess the whole of 

 the tinctorial power of the liquid, which has also lost its yellow colour and bitter 

 taste. Hence, it may be inferred that the substance which imparts to the extract its 

 bitter taste and yellow colour is capable also of giving rise to the formation of a certain 

 quantity of colouring matter. 



In 1837 a memoir was published by Decaisne, containing the results of an ana- 

 tomical and physiological examination of the madder plant, results which were con- 

 sidered so important that a prize was awarded to the author by the Eoyal Academy 

 cf Sciences at Brussels. This investigation led the author to the conclusion, that the 

 cells of the living plant contain no ready-formed red colouring matter, but are filled 

 with a transparent yellow juice, which, on exposure to the atmosphere, becomes reddish 

 and opaque in consequence of the formation of red colouring-matter. Hence he 



