Dr. Schunck on Rubian and its Products of Decomposition. 365 



II. 03785 grm. of the same preparation as the last, heated to 

 the melting-point, gave 0*9465 carbonic acid and 0-1730 water. 



III. 0*4815 grm. obtained directly from madder, dried at 

 100° C, gave 1-2130 carbonic acid and 0-2335 water. 



IV. 0-4290 grm. of the same preparation as the last, heated 

 to the melting-point, gave 1*0735 carbonic acid and 0*2050 

 water. 



V. 0-3120 grm. of another preparation obtained directly from 

 madder, gave 0-7855 carbonic acid and 0-1460 water. 



VI. 0*2350 grm. of the same preparation as the last, gave 

 0*5865 carbonic acid and 0*1065 water. 



In 100 parts it therefore contains — 



Carbon . 

 Hydrogen 

 Oxygen . 



I endeavoured in vain to determine the atomic weight of this 

 substance. Neither the lead nor the baryta compound gave 

 results which harmonized either with one another or with the 

 analyses of the substance itself. There is however only one for- 

 mula which is in accordance with the analyses, and at the same 

 time satisfactorily explains its formation. This formula is 

 C 14 H 6 4 , which requires in 100 parts — 



Carbon .... 68*85 

 Hydrogen . . . 4*91 

 Oxygen .... 26*24 



It may be remarked that this is also the composition of ben- 

 zoic acid • and even if the formula of rubiretine should not be 

 exactly that given above, but perhaps the double or triple of it, it 

 still remains remarkable that two such very different substances 

 should have the same percentage composition. 



The formation of rubiretine from rubian can only be explained 

 in connection with that of vcrantine. If 2 equivs. of verantine, 

 2 equivs. of rubiretine and 12 equivs. of water be added toge- 

 ther, the sum will be equal to 1 equiv. of rubian, as follows : — 



2 equivs. of Verantine =C 28 H 10 O 10 



2 equivs. of Rubiretine = C 28 H 12 O 8 



12 equivs. of Water = H 12 O 12 



1 equiv. of Rubian =C 56 H M O 30 



If this be the correct representation, it follows that verantine 

 and rubiretine stand in an intimate relation to one another, 

 that the formation of one always indicates that of the other. In 

 confirmation of this view, I may state that I have never seen 

 the formation of one of these substances taking place without it 

 being possible to detect the presence of the other. 



