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VII. On the Colouring Matters of Madder. 

 By Dr. Schunck*. 



THE organic colouring matters present such a wide field for in- 

 quiry, that it would require the labour of years to enable one 

 person fully to elucidate their properties, or even to bring this depart- 

 ment of organic chemistry into a state of development proportionate 

 to the present condition of the science. The substances included under 

 the name of colouring matters by no means agree in their chemical 

 characteristics ; they merely coincide in being possessed of certain 

 vivid colours, or in giving rise to coloured compounds. Strictly con- 

 sidered, some of them ought to be classed among the resins and others 

 among the extractive matters ; and on the other hand, if we attempt 

 a definition of the class according to their chemical characteristics, 

 we shall find it impossible to exclude a large number of bodies, which, 

 like tannin and catechin, are capable of giving rise under peculiar 

 circumstances to brown substances, which in nowise differ in their 

 general properties from the bright red colouring matters of archil, 

 logwood, &c. Some colouring matters are presented to us ready 

 formed in the different parts of plants and animals ; others are pro- 

 duced artificially from colourless substances, which undergo very 

 complex changes during the process ; others arise spontaneously 

 during the first stages of oxidation or putrefaction following the ex- 

 tinction of organic life. In the investigation of substances thus 

 widely differing in properties and formation, it would be vain to 

 expect at present anything approaching to general results in regard 

 to the class as a whole. I must therefore content myself on this 

 occasion with giving a short account of the results of some ex- 

 periments which I have made on one branch of the subject, at the 

 same time apologising for their present vague and undefined nature. 



I have directed my attention in the first instance to madder, partly 

 because the colouring matters contained in it are almost unknown, 

 or rather worse than unknown, viz. known in such a manner as 

 merely to mislead those who wish to inform themselves by the ac- 

 counts given of them, and partly because madder is an article of such 

 an immense importance in the art of dyeing that every discovery in 

 relation to it acquires immediately a practical bearing. 



It will be unnecessary for me to allude to the former numerous 

 investigations of madder, except so far as to mention that Robiquet 

 discovered in it a crystallized volatile colouring matter, which he 

 called Alizarin, and that Runge described five colouring matters 

 which he obtained from it, viz. madder purple, madder red, madder 

 orange, madder yellow and madder broivn. I may here state as one 

 result of my investigation, that I agree with Runge in thinking that 

 there is more than one colouring matter in madder, though I am of 

 opinion that the substances which he enumerates and describes are 

 not pure. Before however entering on this part of the subject, I 

 shall first give the results at which I have arrived in regard to ali- 



* From Report of British Association for 1846, 



