THE IMPORTANCE OF SULPHUR. 201 



ments with fermenting wine must, though he raised the point 

 that the collaboration of reducing bacteria was not impossible. 

 In a fermenting must, seven weeks old, he found 49.4 mgrrns. 

 of S0 2 per litre; and two months later 576 mgrms. In view, 

 however, of the determinations of Pfeifer, confirmed by the ob- 

 servations of S. KLAUDI and A. SVOBODA (I.), his statement that 

 the reduction of the sulphates occurs only with thin sowings of 

 yeast and sluggish fermentation cannot be accepted. E. HOTTER 

 (I.) also found 4.5-4 8 mgrms. of S0 2 per litre in cider and 

 currant wines prepared in the laboratory, and certainly not 

 sulphured. 



These discoveries have no small importance for the fermenta- 

 tion technologist and foodstuff chemist, since, until recently, it 

 was usual to consider that beer found to contain sulphur dioxide 

 must have been made from strongly sulphured hops, or else 

 treated with calcium sulphite as a preservative. Similar con- 

 clusions (cask sulphuring or washing with calcium bisulphite) 

 were also formed with regard to wines found to contain sulphur, 

 more especially since L. ROESLER (I.) in 1885 stated that he had 

 never succeeded in detecting sulphur dioxide in wine prepared 

 in the laboratory so as to preclude these sources of sulphur. The 

 present state of our knowledge shows that the matter is different 

 and that great care must be exercised, in this direction also, in 

 judging the results of analysis, a schooling in fermentation 

 physiology being moreover indispensable. Both the sulphur 

 dioxide produced during fermentation and that originating in 

 the sulphuring of the casks is almost entirely converted into a 

 state of combination during the storage of the wine ( 79), so 

 that, as was confirmed by M. RIPPER (I.) and R. KAYSER (L), 

 only extremely minute quantities of free S0 2 , mostly inferior to 2 

 mgrms. per 100 c.c., are present in wine that is ready for 

 bottling. This free dioxide alone comes under consideration in 

 judging wine from the medico-physiological standpoint, and not 

 that present as aldehydic sulphur dioxide, which is not merely 

 innocuous to health according to the researches of J. MARISCHLER 

 (I.) but really essential to the bouquet of the wine. In con- 

 sequence of the reducing power of the dioxide, the presence of 

 larger quantities in beer or wine affects the results of sugar 

 determinations with Fehling's solution, causing, as was first 

 pointed out by Jos. HERZ (I.), the sugar values to come out in 

 excess of the truth. 



In certain circumstances the reduction of the sulphates in the 

 nutrient solution by the activity of yeast may proceed a stage 

 further than the formation of the dioxide, namely, to the pro- 

 duction of sulphuretted hydrogen. However, the first report on 

 this point, as made by CROUZEL (I.), was found inaccurate when 

 tested by F. GAY (I.), though confirmed by the researches of 

 NASTUKOFF (I.) with pure cultures. A solution of 10 per cent, of 



