192 



MINERAL FOODSTUFFS. 



similar conditions, to only 52.2 and 48.9 per cent, respectively. 

 Hence the increased potassium content of the wort resulted in a 

 reduced attenuation. In tests carried out by R. KUSSEROW (I.), 

 the addition of dipotassium phosphate (K 2 HP0 4 ) had no apparent 

 influence on the fermentation of the wort ; but here the effect of 

 the potassium alone could not be judged, owing to the simultaneous 

 presence of the phosphoric acid of the salt. According to the 

 observations of C. G. MATTHEWS (II.), potassium is more readily 

 assimilated when a portion is present in the condition of sulphate 

 than when the phosphate alone is used. Compare also the state- 

 ment of A. MAYER (I.) on this point. 



Before proceeding to discuss the importance of the aforesaid 

 three elements in connection with the life and action of yeast, it 

 will be necessary to deal with two points of special interest to the 

 chemist and fermentation technologist, namely, the percentage 

 and the quantitative and qualitative composition of the ash con- 

 stituents of yeast. 



With regard to the ash content, numerous determinations are 

 available, a few of which, referred to the dry matter of the yeast, 

 are given below : 



PERCENTAGE OF ASH IN YEAST. 



Top fermentation 



Yeast . 

 Analyst 



Bottom Yeast 

 Analyst- 



Bottom Yeast (cont.) 

 Analyst 



7.61 8.76 7.7 10.1 



C. Lintner, Seyffert, BCHAMP Hessen- 

 Weihenste- St. Peters- (VI.) land, 

 phan. burg. 



These figures are not all equally reliable. For instance, the 

 remarkably low figures given by Liebig's pupil, J. SCHLOSS- 

 BERGER (I.) are due to the fact that the yeast samples were not 

 only washed very clean with plenty of water, before drying and 

 incinerating, but were also " purified " with cold and hot water, 

 and with ether, as though dealing with a precipitate of the cha- 

 racter of ferric hydroxide, instead of delicate cells with permeable 

 walls. Other workers, though proceeding with greater care, have 

 mostly overlooked the fact that the sedimental yeast they obtained 

 from the brewery for the purposes of their experiments does not 

 consist exclusively of yeast cells, but contains all sorts of other 

 matters ( 245, 254, 255), only a few of which are removed by 

 washing and sifting, so that a considerable difference exists 

 between the ash of yeast, per se t and that of ordinary eedimental 

 yeast* 



