Dr. Schunck on Rubian and its Products of Decomposition. 499 



These experiments also confirm the view derived from analyti- 

 cal results, that there is a mutual relation and interdependence 

 on the one hand between rubiretine and verantine, and on the 

 other between rubiafine and rubiagine and the sugar, whereas 

 alizarine occupies an independent position; for rubiretine is 

 never found among the products of decomposition by fermen- 

 tation without an accompaniment of verantine, though both 

 may be present to the exclusion of all other products ; and the 

 formation of sugar always indicates that of rubiafine or rubiagine, 

 whereas all these substances may be present without a trace of 

 alizarine being at the same time produced. 



The deleterious eficct resulting from the presence of acids in 

 the dye-bath during the process of madder dyeing hereby finds 

 an additional explanation. Not only do acids act injuriously by 

 seizing hold of the mordants with which the colouring matter 

 ought to combine, not only do they allow the constituents of the 

 root which are injurious in the process to have full scope by de- 

 priving them of the alkalies or alkaline earths with which they 

 would otherwise unite, but they also retard the peculiar process 

 by which the alizarine is formed, and even lead to the formation of 

 deleterious substances at the expense of the colouring matter itself. 

 In order to place in a more striking light the influence exerted 

 respectively by acids and alkalies during the process of the fer- 

 mentation of rubian, I will here give the results of an experiment 

 to ascertain quantitatively the amount of the various products of 

 decomposition formed on the addition of either during the pro- 

 cess. For this purpose I took 5'59 grms. rubian, dissolved it 

 in water, added to the solution a quantity of ferment, and mixed 

 both together very well. I then divided the mixture into two 

 equal parts, and added to one half a small quantity of carbonate 

 of soda, to the other a little sulphuric acid. Both were allowed 

 to ferment for a length of time, and the portion insoluble in 

 water was treated in both cases with boiling alcohol. The alcohol 

 deposited on being filtered boiling hot a quantity of rubiafine, 

 which was collected on a filter and weighed. To the alcoholic 

 liquid I added acetate of alumina. The precipitate thereby occa- 

 sioned was separated by filtration, washed with alcohol and 

 decomposed with boiling muriatic acid. The red flocks thus 

 obtained were collected on a filter, washed, dried and weighed. 

 They consisted of alizarine, verantine and rubiafine. After being 

 weighed, they were treated with boiling dilute nitric acid, which 

 destroyed the alizarine, leaving the two other substances behind 

 in the shape of a yellow powder, which was filtered, washed, 

 dried and weighed. By deducting its weight from the total 

 weight of the three, the weight of the alizarine was ascertained. 

 The liquid filtered from the alumina precipitate deposited on the 



