THEORY OF FERMENTATION 377 



found that whilst saccharomyces pastorianus effected a 

 complete fermentation of the sugar, the caseous ferment 

 did not decompose more than two-thirds, and the ferment 

 we have designated new " high " ferment not more than 

 one-fifth : and keeping the flasks for a longer time in the 

 oven had no effect in increasing the proportions of sugar 

 fermented in these two last cases. 



We conducted a great number of fermentations in 

 mineral media, in consequence of a circumstance which it 

 may be interesting to mention here. A person who was 

 working in our laboratory asserted that the success of our 

 experiments depended upon the impurity of the sugar- 

 candy which we employed, and that if this sugar had been 

 pure much purer than was the ordinary, white, commer- 

 cial sugar-candy, which up to that time we had always 

 used the ferment could not have multiplied. The per- 

 sistent objections of our friend, and our desire to con- 

 vince him, caused us to repeat all our previous experi- 

 ments on the subject, using sugar of great purity, which 

 had been specially prepared for us, with the utmost care, 

 by a skilful confectioner, Seugnot. The result only con- 

 firmed our former conclusions. Even this did not satisfy 

 our obstinate friend, who went to the trouble of preparing 

 some pure sugar for himself, in little crystals, by repeated 

 crystallizations of carefully selected commercial sugar- 

 candy; he then repeated our experiments himself. This 

 time his doubts were overcome. It even happened that the 

 fermentations with the perfectly pure sugar instead of being 

 slow were very active, when compared with those which we 

 had conducted with the commercial sugar-candy. 



position of such a medium. It is this that we call here " Raulin's liquid " 



for abbreviation. 



Water 1,500 



Sugar candy 70 



Tartaric acid 4 



Nitrate of ammonia 4 



Phosphate of ammonia 0.6 



Carbonate of potassium 0.6 



Carbonate of magnesia 0.4 



Sulphate of ammonia 0.35 



Sulphate of zinc 0.07 



Sulphate of iron 0.07 



Silicate of potassium 0.07 



J. Raulin, Paris, Victor Masson, 1870, TMtt four Ic doctoral. 



