INDUSTRIES DEPENDING ON PLANT PRODUCTS I6S3 



was added directly, to the second after heating to 80^ C. to kill the 3-east 

 and then coohng, and to the third after filtering to remove completely the 

 yeast. After standing for 48 hours, anahsis shewed no difference between 

 the three portions for all contained 20 mgms. of free sulphur dioxide and 

 176 mgms. of it combined. So the presence of yeast has no influence on 

 the amount of sulphur dioxide that enters into combination when the fer- 

 mentation is stopped, if the quantit}' added has been sufiicient to stop 

 fermentation at once. Nevertheless, with a view to the later preservation 

 of the wine, it is better to eUminate by a preliminary^ racking the thick 

 lees at the bottom of the cask, for this might give rise to a slow fermenta- 

 tion which would carrj- off the free sulphur dioxide. 



The different factors which cause variation in the amount of combined 

 sulphur dioxide have been examined, and the results are drawn up in 

 Table VI. 



Table VI. — Different factors that regulate the amount oi sulphur dioxide 

 that enters into chemical combination. 



' Total Combined ^d^hvde Alcohol Sugar 



History of wine ??'P?"' ^"^P^'^^ 



.»^»okv.Aj ^ -.u^ dioxide dioxide ,-x ^ ..x 



",."'' " "7."''^ per litre per cent per litre 



per litre per litre *^ *^ '^ 



tngtns. 



IFennented 200 



Fermented 196 



Without precipitation ....... 182 



g \ After precipitation 324 



Preserved normally 296 



i Refermented 424 



Monbazillac i After several precipitations 392 



Wine (without precipitation. . . 220 



Cfl 



The preservation of some wines of Gironde for about a year were studi- 

 ed, the amount of sulphur dioxide being kept constant by successive ad- 

 ditions. It appears that its preservation during two 5'ears can be secured 

 by a small total amount of sulphur dioxide if it is added at intervals. 



Conclusions. — The following conclusions may be drawn from these 

 experiments : 



i) Sulphurous acid added to grape must soon enters into chemi- 

 cal combination, partly or wholely. The sugar absorbs most of it, but only 

 the glucose, for the fructose is inactive. Other ingredients of the must can 

 also combine with it in measurable quantities which depend on the nature 

 of the must. In an ordinary' mu.st when the quantity of sulphur dioxide 

 added reaches lOO mgms. per litre, complete combination no longer takes 

 place, and the proportion of combined sulphur dioxide to total sulphur 

 dioxide decreases as more is added. A state of equilibrium between the free 



