the Ferment of Madder on Sugar. 163 



water to the solutions to be fermented, as I found that the fer- 

 mentation was much promoted by this addition. 



Most of my experiments were made with cane-sugar, but I 

 have also subjected grape- and milk-sugar to the same process 

 of decomposition. In operating on cane-sugar I proceeded 

 in the following manner. The sugar having been dissolved in 

 water, I added to the solution for every pound of sugar taken 

 about four quarts of the brown pulp, prepared as just described, 

 and a sufficient quantity of lime-water to change the colour of 

 the ferment from brown to dark purple, and to cause a slight 

 alkaline reaction in the liquid. The whole having been well 

 mixed, was left to itself. The vessels which I employed for 

 conducting the operation in, were large earthenware mugs. In 

 warm summer weather, provided the quantity of materials taken 

 was not too small, the fermentation generally commenced on the 

 succeeding day. A copious disengagement of gas took place, 

 and continued for a number of days. The bubbles of gas, in 

 rising, formed, together with particles of ferment carried up by 

 them, a thick scum on the surface of the liquid, resembling the 

 froth on the surface of fermenting beer. As far as the evolu- 

 tion of gas, however, was concerned, the action did not seem 

 to be quite as energetic as would have been produced by the 

 action of ordinary yeast on sugar. During this stage of the 

 fermentation a slight vinous odour might be perceived near the 

 surface of the liquor. After a few days the liquid began to 

 acquire a decided acid reaction, which was first indicated by the 

 colour of the ferment changing from purple to brown. Very 

 soon litmus paper began to be strongly reddened by it. After 

 some time the disengagement of gas ceased, and the particles of 

 ferment all sank to the bottom, leaving a clear, yellowish, super- 

 natant liquid. The latter, however, on standing exposed to the 

 atmosphere, seemed constantly to acquire more and more acid pro-* 

 perties ; and after several weeks' exposure, it was generally found 

 to have a strongly acid taste, and smell like that of sour beer. 

 I have generally allowed the mixture to stand for several months, 

 usually from summer to winter, as I imagined that long stand- 

 ing promoted the formation of one of the acid products, whose 

 properties I shall presently describe. Nevertheless, during this 

 lapse of time little or no mould was formed on the surface of 

 the liquor, no decidedly putrid smell was emitted, nor did the 

 mass ever seem to be particularly attractive to insects, or to 

 breed worms or larvae, at least none that were visible to the 

 naked eye. 



Now the products of this process of fermentation are of three 

 kinds; gaseous, liquid, and solid. I shall describe them in the 

 order mentioned. For the purpose of examining the gaseous 



M2 



