CHANGES IN EXPRESSED YEAST JUICE. 469 



Although the yeast juice of itself, and particularly in view of 

 the large proportion of added sugar, is bound to restrict the 

 development of micro-organisms, it has been considered advisable 

 to add some antiseptic in carrying on fermentations with the 

 juice. According to BUCHNER (X.), corrosive sublimate renders 

 yeast juice very turbid and destroys the fermentative power ; and 

 it is stated by BUCHNER and ANTONI (I.) that the same effect is 

 produced by even a 0.55 per cent, solution of ammonium fluoride 

 or sodium fluoride. Sodium azoimicle (dose 0.36-0.71 per cent.) 

 diminishes the fermentative power, whereas the converse result 

 is reported of a 0.5 per cent, solution of quinine sulphate 

 by PALLADIN (I.), GROMOW and GRIGORIEW (I.) and also by 

 BUCHNER and ANTONI (I.). 



It is well known that hydrocyanic acid temporarily arrests the 

 activity of most enzymes completely, the effect passing off when 

 the volatile acid has been expelled by passing a current of air 

 through the liquid. This behaviour has also been observed by 

 BUCHNER and RAPP (I.) with the enzymes of alcoholic fermenta- 

 tion. In the earlier experiments of these workers (1-4), in yeast 

 juice fermentations, extensive use was made of arsenites (see 

 p. 244, vol. ii.) as antiseptics, but these were afterwards abandoned. 

 In this connection, Abeles has pointed out that substances entering 

 into direct combination with the proteids of yeast juice an 

 observation previously made by BIERNACKI (I.) lose their toxic 

 properties toward micro-organisms, and that 2 per cent, of sodium 

 arsenite is incapable of restricting either the growth or the 

 fermentative power of the cells, a portion of the latter being still 

 active after the fixation of the arsenite. In consequence of this 

 observation the use of arsenites was abandoned, more particularly 

 because of their irregular action on fermentation under certain 

 conditions. For instance, an addition of 2 per cent, of arsenite 

 prevented fermentation by yeast juice when the yeast had been 

 stored, or the juice had been dialysed or diluted, or finally when 

 dried juice (prepared at 35 C.) was used. BUCHNER and 

 RAPP (VII.) attribute this peculiar behaviour to the disappear- 

 ance or diminution of the high molecular proteids, so that 

 proteids afford a certain amount of protection against the in- 

 jurious action of arsenite, the same effect being produced by sugar 

 when added in considerable quantity with, or directly after, the 

 arsenite. The addition of 5 per cent, of arsenite completely 

 arrests the fermentative power of the juice. 



The influence of formaldehyde was investigated by WROB- 

 LEWSKI (IV.), who found that an addition of 0.05 per cent, 

 reduced the fermentative action to a very low level, whereas 

 MACFADYEN, MORRIS and ROWLAND (I.) observed a favourable 

 effect with an addition of 0.0005 per cent. BUCHNER and 

 ANTONI (I.) found that the fermentative power was reduced to 

 one-fifth by 0.12 per cent., and to between one-third and three- 



