Dr. Scliunck on Rubian and its Products of Decomposition. 497 



again filtered left on evaporation a quantity of sugar mixed with 

 sulphate of soda. The mixture of ferment with the products of 

 decomposition yielded to boiling alcohol a large amount of 

 rubiafine, rather more than the average quantity of alizarine, 

 and a moderate quantity of rubiretine and verantine, but no 

 rubiagine. I repeated this experiment^ using caustic soda instead 

 of carbonate of soda; but having employed rather too large a 

 quantity of alkali, I found that the action of the ferment was 

 very much retarded, so much so that after standing for sOme 

 days there was still a quantity of undecomposed rubian present ; 

 and among the products of decomposition formed there was little 

 or no alizarine, rubiafine or rubiagine, but a large quantity of 

 rubiretine and verantine. The addition of lime water produced 

 a similar effect to that of carbonate of soda, though of not quite 

 so marked a character. 



Having mixed a solution of rubian with ferment in the usual 

 manner, I added a small quantity of sugar of lead. The ferment, 

 which had been previously diffused through the liquid, was im- 

 mediately precipitated by the lead salt in brown flocks, leaving a 

 clear yellow solution floating above it. After standing however 

 for some days the colour of the solution became gradually paler, 

 and at length almost disappeared. After filtration and evaporation 

 it left a small quantity of sugar. The mass left on the filter was 

 purple, and contained oxide of lead. It was treated with cold 

 sulphuric acid, which turned it red. The acid liquid after filtra- 

 tion was neutralized with carbonate of lead, and again filtered, 

 when it appeared colourless, and produced no precipitate with 

 basic acetate of lead, a proof that it contained no rubian. The 

 mass which had been treated with cold sulphuric acid, was then 

 treated with boiling alcohol, which on being filtered and allowed 

 to cool deposited some crystallized rubiafine, and was found to 

 contain a trace of alizarine and a large quantity of rubiretine 

 and verantine. It appears therefore that even sugar of lead, 

 which produces an insoluble compound with the ferment, is 

 incapable of arresting the action of the latter on rubian. 



The same experiment was made, using corrosive sublimate 

 instead of sugar of lead. The action of the ferment was in this 

 case considerably retarded, for the yellow colour of the liquid 

 did not entirely disappear, even after several days. The filtered 

 liquid left on evaporation some corrosive sublimate with a little 

 rubian, but no sugar. The mass on the filter was treated with 

 boiling alcohol, which was then found to contain no alizarine, 

 rubiafine or rubiagine, but a considerable quantity of rubiretine 

 and verantine. 



Arsenious acid had a very similar effect to sugar of lead and 

 corrosive sublimate, that is to say, it retarded the action of the 



