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INDUSTRIES DEPENDING ON PLANT PRODUCTS 



under certain conditions the contrary is the case, especially when ferment- 

 ing must or re-fermenting sweet wine contains a high proportion of com- 

 bined sulphurous acid. 



One experiment shews clearly the influence of the sulphurous acid 

 on the selective aflfinity of the yeast. But it is impossible to say whether 

 this is due to a temporary modification of the protoplasm or to a survival 

 of the fittest among the yeasts. 



IV. — The chemical combination of sulphurous acid in wines. 

 Wine and must made from healthy grape and from grape infected by Bo- 

 trytis cinerea were compared, and the results shewn in Table V. were ob- 

 tained. 



Table V. — .4 comparison of must with wine. 



Free sulphur dioxide 

 Combined ...... 



Total . 



In both cases the power of wine for combining with sulphurous acid 

 was ver\' little different from that of the must; it was slightly higher because 

 of the existence of traces • of aldehyde in the former. 



Experiments were also made on the capacity* for combining with sul- 

 phur dioxide of wines which have fermented in the presence of sulphur 

 dioxide. From the same must two specimens of wine were prepared, N" i, 

 a control specimen, and Xo 2, which had been allowed to ferment in the pre- 

 sence of sulphur dioxide and which contained 296 mgms. sulphur dioxide 

 and 220 mgms. aldehyde per litre. To both wines about 2 mgms. sulphur 

 dioxide was added, and after 48 hours they proved to have the following 

 amounts of sulphur dioxide. 



184) 



Total sulphur dioxide . 



188 



496 



This shews that X© 2 has in a combined state only a little more of 

 the sulphur dioxide subsequently added than has X^ i. 



The checking of fermentation. — A Utre of fermenting wine contain- 

 ing still 80 gms. of sugar per litre was divided into three parts, and to 

 each part was added 66 mgms. of sulphui dioxide. To the first portion this 



