192 Dr. Schunck on the Constitution of 



existence of this colouring matter, that by acting on it with 

 nitric acid no rubiretine is formed, but that the second product 

 of decomposition, which is obtained as an insoluble yellow powder, 

 consists of verantine only. 



From the circumstance that rubian as well as alizarine, when 

 decomposed by nitric acid, yield no other solid product but 

 phtalic acid, and considering that alizarine is in every case a 

 derivative of rubian, I inferred that it would be possible, if not 

 experimentally at least theoretically, to convert rubian entirely 

 into alizarine ; that by this conversion none of the carbon of the 

 rubian is eliminated ; that the whole of this element enters into 

 the composition of the alizarine formed, and that, in fact, the 

 two bodies differ from one another merely by the elements of 

 water. This conclusion, which I consider to be the most import- 

 ant result of my investigation, derives confirmation from the 

 experiments made by me on the action of ferments on rubian. 

 I have found that, by the action of emulsine on rubian, though 

 only a portion of the latter is decomposed, still that portion yields 

 almost pure alizarine. Again, when the action of erythrozym 

 on rubian is retarded by the addition of some antiseptic substance, 

 such as corrosive sublimate or alcohol, the rubian is entirely 

 decomposed, though much more slowly than without such addi- 

 tion. In its results, however, the action is very different. If 

 the retardation was very great, then the only products of decom- 

 position formed are rubiretine and verantine, without a trace of 

 alizarine, sugar, or any other body. If the action was mode- 

 rately retarded, then besides rubiretine and verantine, sugar and 

 rubiafine or rubiagine are found among the products of decom- 

 position ; but in no case can more than a trace of alizarine be 

 discovered. By the addition, however, of a small quantity of 

 alkali during the process of fermentation, the quantity of aliza- 

 rine formed is very much increased. From these experiments 

 it must be inferred that the quantity of each product of decom- 

 position which rubian is capable of forming is by no means con- 

 stant ; that rubian may yield, according to circumstances, either 

 alizarine alone, or rubiretine and verantine alone, or rubiafine and 

 sugar alone. The decomposition of rubian, therefore, cannot be 

 represented by one equation, it must be represented by three equa- 

 tions. In one of these equations the rubiafine may be replaced by 

 rubiagine, which is an occasional product of the fermentation of ru- 

 bian, or by rubiadine when an alkali is the decomposing agent, or 

 by rubianine when the decomposition is effected by acids; for these 

 bodies differ from one another in composition merely by the ele- 

 ments of water ; and they are so similar in their properties, that 

 it is evident they must belong to the same class of compounds. 

 To represent the decomposition by one equation, as M. Laurent 



