Dr. Schunck on Rubian and its Products of Decomposition. 423 



0*2500 grm. of the dry substance gave 0*6380 carbonic acid 

 and 0*0960 water. 



II. 0*4220 grm., obtained by allowing an extract of madder 

 with tepid water to ferment, lost, on being heated, 0*0750 water 

 = 17*77 per cent. 



0*3225 grm. of the dry substance gave 0*8230 carbonic acid 

 and 0-1170 water. 



These numbers correspond in 100 parts to — 



T. II. 



Carbon .... 69*59 69*59 



Hydrogen . . . 4*26 4*03 



Oxygen .... 26*15 26*38 



The quantity of rubiretine and verantine formed by the fer- 

 mentation of rubian does not seem to be so large as it is, when 

 acids or alkalies are employed for its decomposition, and as the 

 process of separating and purifying the products of fermenta- 

 tion is, on account of the number of products formed, rather 

 more complicated, the quantity of each substance obtained in a 

 pure state is but small. The following analyses of these two 

 substances were made with specimens obtained by the fermenta- 

 tion of an extract of madder ; and even by preparing them in 

 this manner I had some difficulty in procuring a sufficient 

 quantity for examination, because the rubiretine formed by 

 fermentation is always found mixed with rubiadipine, from 

 which it is with difficulty freed ; and the verantine is for the 

 most part obtained in combination with oxide of tin, from which 

 I have found it impossible to separate it. 



0*3445 grm. rubiretine gave 0*8580 carbonic acid and 0*1695 

 water. 



This gives in 100 parts — 



Carbon 67*92 



Hydrogen 5*46 



Oxygen 26*62 



0*3705 grm. verantine gave 0*9010 carbonic acid and 0*1420 

 water. 



In 100 parts- 

 Carbon ...... 66*32 



Hydrogen 4*25 



Oxygen 29*43 



The great excess of carbon in this analysis indicates an ad- 

 mixture of alizarine. This proceeds from the circumstance that 

 the method of separating verantine and alizarine, by means of 

 acetate of copper, is not absolute. When these two substances 

 are present together in solution, acetate of copper precipitates a 

 portion of the alizarine together with the verantine, and the latter 



