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



or 



1 eq. Sugar . = C 12 H 12 12 \ _ TC^H^O 30 ^ eq. Rubian. 

 1 eq. Rubianine = C^H^O 20 J ~ \ H 2 O 2 = 2 eqs. Water. 



C56 H 36Q32 C 56 H 36Q32 



The formula C 44 H 24 O 20 seems to me the more probable of 

 the two. It agrees best with the results of analysis, and the 

 high atomic weight of rubianine which follows from it explains 

 the very neutral character of that substance. Hence it appears 

 that rubianine stands in the same relation to the sugar as rubi- 

 retine does to verantine. When added together they contain 

 the elements of rubian plus the elements of water, while rubire- 

 tine and verantine added together contain the elements of rubian 

 minus the elements of water. 



On the whole, it appears that the action of acids on rubian is 

 not of so complicated a nature as might at first sight be sup- 

 posed. The number of substances produced by this action is 

 five. Nevertheless it does not follow that these five substances 

 are all formed together, or in other words, that one atom of ru- 

 bian by its decomposition gives rise to all five at the same time. 

 From the composition of these substances, as compared with that 

 of rubian, it follows that the latter by the action of acids under- 

 goes decomposition in three different directions, or more correctly 

 speaking, that the decomposition affects three separate atoms of 

 rubian. One of these atoms loses 14 atoms of water, and is 

 converted into alizarine. The second loses 12 atoms of water, 

 and then splits up into verantine and rubiretine. The third 

 takes up the elements of water, and then splits up into rubianine 

 and sugar. What the circumstances are under which either one 

 or the other of these three processes takes place I am unable to 

 say. That the loss of a greater or smaller proportion of water or 

 the addition, on the contrary, of the elements of water to those of 

 rubian, are the immediate efficient causes of one or the other of 

 the three processes taking place is very probable ; but what again 

 determines the elimination of more or less water from rubian, 

 or, on the other hand, its combination with more water, remains 

 uncertain. It is not unlikely however that the degree of tem- 

 perature at which the decomposition is effected may have some- 

 thing to do with it. It is probable that the lower the tempera- 

 rature at which the acid acts on the rubian, the more rubianine and 

 sugar are formed, and that at a higher temperature more aliza- 

 rine, verantine and rubiretine arc produced. In all experiments 

 hitherto mentioned I have always obtained all five products of 

 decomposition, though by no means in equal proportions, the 

 alizarine being formed in the smallest quantity, the amount of 

 rubiretine and verantine being somewhat greater, and the rubia- 



