the Ferment of Madder on Sugar. 165 



pearance of being traversed with silky bands. On filtering, 

 these scales remained on the filter, but their quantity was so 

 insignificant that they could not again be separated from the 

 paper. 



The liquid remaining in the retort after the second distillation 

 was added to that remaining after the third distillation, and 

 evaporated together with an excess of carbonate of soda until 

 the bulk was very much diminished. The liquid was then su- 

 persaturated with sulphuric acid and distilled. The distillate 

 was colourless, but had a strong acid taste and reaction. It was 

 neutralized with carbonate of soda, and then gave on evaporation 

 a crystalline mass, which was white with a brownish tinge. This 

 mass, when treated with boiling dilute sulphuric acid, evolved a 

 pungent smell like that of acetic or formic acid. Its watery 

 solution gave reactions similar to those of formiate of soda. It 

 gave, for instance, with nitrate of silver a white crystalline pre- 

 cipitate, which soon became black when left to stand, but imme- 

 diately on boiling the liquid; with protouitrate of mercury, a 

 white crystalline precipitate, which on standing was slowly re- 

 duced to gray metallic mercury ; and with corrosive sublimate it 

 produced, on boiling, a copious deposit of white crystalline scales 

 (calomel). But on adding acetate of lead, evaporating to dry- 

 ness, and treating the residue with alcohol, no crystals of for- 

 miate of lead were left undissolved. I therefore concluded that 

 the salt consisted for the most part of acetate of soda, contami- 

 nated with some impurity, which obscured the reactions proper 

 to acetic acid. Whether the acetic acid thus obtained is a pro- 

 duct of the direct action of the ferment on sugar, or whether it 

 is formed indirectly from the oxidation of the alcohol produced 

 in the first instance, is uncertain. The greater part of the acid 

 found in the fermented liquor after exposure for some time, in 

 quantities so considerable as to impart to the liquid a strong 

 acid taste and smell, is without doubt derived from the latter 

 source. 



The last product of this process of fermentation which I shall 

 have to mention is solid, and though the most interesting of 

 them all, is formed in such small quantities as to render its 

 identification difiicult. In order to obtain an appreciable quan- 

 tity of it, it is necessary to employ several pounds of sugar. The 

 solution of sugar being mixed with ferment and lime-water in 

 the proportions stated above, the mixture is allowed to ferment, 

 and to stand for several weeks at least, after the disengagement 

 of gas has ceased. The liquid is then strained through calico, 

 and the ferment which remains on the calico in an apparently 

 unchanged state, is washed with water until the percolating 

 liquid is no longer acid. The liquid is then rendered alkahne 



