188 Dr. Schunck on the Constitution of 



from madder, either by myself or others, may be produced from 

 rubian; and I think, therefore, I am justified in considering 

 this substance as the link which unites them all together in one 

 system. No formula can be proposed for any one of them which 

 is not in accordance with that of the parent substance. By the 

 action of sulphuric or muriatic acid rubian is decomposed into 

 alizarine, verantine, rubiretine, rubianine and sugar, in accord- 

 ance with the following equations : — 



Rubian. Alizarine. 



1. C^H 34 O 30 =:4C 14 H 5 O 4 + 14HO. 



Rubian. Verantine. Rubiretine. 



2. C^H 34 O 30 =2C 14 H 6 5 + 2C 14 H 6 O 4 + 12HO. 



Rubian. Sugar. Rubianine. 



3. C 56 H 34 O 30 +9HO = 2C 12 H 12 O 12 +C 32 H 19 O 15 . 



By decomposition with alkalies, rubian yields the same pro- 

 ducts with the exception of rubianine, which is replaced by a 

 similar body, rubiadine, differing from the former by the elements 

 of 7HO. 



Rubian. Sugar. Rubiadine. 



4. C 56 H 34 O 80 + 2HO = 2C 12 H l2 O 12 + C 32 H 12 O 8 . 



By the action of a peculiar fermentative substance contained 

 in madder, which I have called erythrozym, rubian also under- 

 goes complete decomposition. The products are in the main the 

 same, but the rubianine and rubiadine of the preceding processes 

 are replaced by two substances of very similar properties, differ- 

 ing from one another and from the two former in composition 

 by the elements of HO. These two bodies I have called rubia- 

 fine and rubiagine. 



Rubian. Sugar. Rubiafine. 



5. C % H 34 30 + 3HO=2C 12 H 12 12 + C 32 H 13 9 . 



Rubian. Sugar. Rubiagine. 



6. C 56 H 34 O 30 + 4HO = 2C 12 H 12 O 12 + C 32 H 14 O 10 . 



For rubiacine and rubiacic acid, which I have proved to be 

 derivatives of rubiafine, I have adopted the formula? C 32 H n O 10 

 and C 32 H 9 O 17 ; for rubiacate of potash, C 32 H 8 16 + KO. 



Now to these formulae M. Laurent has brought forward objec- 

 tions, and he proposes new ones. For rubian he proposes the 

 formula C 32 H 18 18 ; for alizarine, C 10 H 3 O 3 ; for rubiretine, 

 Cio H 4 3 . for rubianine, C 20 H 11 O 9 ; for verantine, C 20 H 7 O 7 ; 

 for rubiacine, C 18 H 6 6 ; for rubiacic acid, C 18 H 5 9 ; and for 

 rubiacate of potash, C 18 H 4 * 8i + £KO. The following equation 

 would explain, according to M. Laurent, the formation of aliza- 

 rine and rubiretine from rubian : — 



