the Ferment of Madder on Suffar. 169 



the lead was precipitated, and then filtered and evaporated. A 

 sweet brown syrup was left, consisting apparently of undecom- 

 posed sugar, which, though allowed to stand for a length of time, 

 yielded no trace of anything crystalline. Part of this syrup 

 being redissolved in water, and the solution being again evapo- 

 rated with the addition of acetate of zinc, no crystals were formed, 

 and the residue left after evaporation was completely soluble in 

 alcohol — a proof of the absence of lactic acid. 



The products resulting from this process of decomposition are 

 therefore the following: — carbonic acid, hydrogen, alcohol, 

 acetic acid, and succinic acid. Of these the last-named is the 

 most remarkable ; and its formation, though it has been observed 

 in other processes of fermentation, is still so uncommon as to 

 call for some further observation. 



I have discovered that on allowing grape-sugar, or sugar of 

 milk, to ferment together with erythrozym and lime-water in the 

 same way as cane-sugar, succinic acid is also formed. Indeed, 

 from sugar of milk I obtained in one experiment more than 

 three times as much of this acid as was ever afforded under the 

 most favourable circumstances by the same quantity of cane- 

 sugar. From 1 lb. of cane-sugar I never obtained more than 

 3| grs. of acid. In the experiment just referred to, I obtained 

 from -^ lb. of sugar of milk nearly 6 grs. of acid. The quanti- 

 ties formed, even under apparently the same circumstances, were, 

 however, very variable. Large quantities of cane-sugar some- 

 times yielded only traces of acid, while smaller quantities gave 

 proportionally a large amount. It is during the later stages of 

 the fermentation, I imagine, that the acid is chiefly formed. At 

 least, I have always found that its amount was greater after the 

 fermenting liquid had stood for several weeks or months than 

 during the first period of the fermentation, when the disengage- 

 ment of gas was most active. Whether the access of atmospheric 

 air is necessary for, or promotes the formation of, the succinic 

 acid, I am unable to say. I may mention, that the phsenomena 

 attending the fermentation of grape-sugar and sugar of milk are 

 apparently the same as when cane-sugar is employed. 



In order to be quite sure that the formation of the succinic 

 acid and the other products was due to the action of the ferment 

 on the sugar, and not to the decomposition of the ferment itself, 

 I have repeatedly allowed mixtures of the ferment and lime-water, 

 without the addition of sugar, to stand exposed to a warm tem- 

 perature and under the same conditions under which the fer- 

 mentation was usually conducted. In this case little or no gas 

 was disengaged, the liquid never became acid, and the ferment 

 remained purple and sank to the bottom of the vessel. After 

 standing for several weeks, the filtered liquid gave with sugar of 



