418 Dr. Schunck on Rubian and its Products of Decomposition. 

 These formulae require respectively in 100 parts — 



Carbon .... 71*64 71-93 



Hydrogen . . . 4*47 4-08 



Oxygen • . . . 23-89 23*99 



If the first formula be the correct one, then the formation of 

 rubiadine is due to the splitting up of 1 equiv. of rubian, after 

 the assimilation of 2 equivs. of water, into 1 equiv. of rubiadine 

 and 2 equivs. of sugar, as will be seen by the following equa- 



xcq. of Rubian. 

 2eqs.ofWater. 



tion : — 



2eqs.ofSugar rrrC^^H^^O^n _ rc5«H**03o=l 



leq.ofRubiadine=C32Hi«0 ' J "" \ H ^0 ^=2 



If the formula of rubianine be C^* H^^ 0^^, rubiadine will diflfer 

 from it by containing the elements of 7 equivs. of water less. 

 If the formula of rubiadine be C^^H^^O'^, then its formation 

 would presuppose the splitting up of 1 equiv. of rubian into 

 1 equiv. of rubiadine, 1 equiv. of sugar and 7 equivs. of water, 

 for 



C44Hi5on4.Ci2Hi2 0i2 + 7HO = C^H34 0«>. 



It appears therefore that the action of alkalies on rubian differs 

 in its results from the action of acids only in one respect, that 

 alkalies as well as acids give rise to the formation of live distinct 

 products of decomposition, that four of these are in both cases 

 perfectly identical, and that the fifth substance produced by the 

 action of acids is replaced in the case of alkalies by another, which, 

 though perfectly distinct, is so similar both in properties and 

 composition, that it may be considered as in every respect its 

 equivalent. 



Action of Ferments on Rubian. — It has long been suspected 

 by chemists that the colouring matter of madder owes its forma- 

 tion to some process of fermentation, but the exact nature of the 

 process has hitjierto remained unknown. Mr. Higgin first 

 pointed out the fact, that a formation of colouring matter takes 

 place even during the short period occupied in the process of 

 dyeing, and he attributes it to the action of some albuminous 

 substance contained in madder on xanthine. That some process 

 of decomposition takes place on extracting madder with cold or 

 tepid water and exposing the extract to a moderate temperature, 

 is proved by the fact that the extract, if concentrated, becomes 

 after some time thick and gelatinous; and that the process 

 of decomposition takes effect chiefly on the rubian is apparent, 

 since the extract, after it has become gelatinous, is found to have 

 lost its bitter taste and the greater part of its yellow colour. 



