INDUSTRIES DEPENDING ON PLANT PRODUCTS 



1677 



the same difference between the two states as regards harmful properties 

 when imbibed, and the regulations concerning the addition of sulphurous 

 acid to fermented drinks have been made with this in mind. 



All compounds formed by sulphurous acid in grape must or wine are 

 unstable. They can be destro^'ed, and the sulphur dioxide completely 

 expelled by heating the liquids to boiling. 



The following points have been examined: 



I. — The chemical combination of sulphurous acid when added 

 TO grape MUST. — The most important ingredient of musts which com- 

 bines with sulphurous acid is the sugar, a mixture of glucose and fructose. 

 X. RoCQUES shewed some time ago that though saccharose does not 

 combine with sulphurous acid, yet invert sugar combines very easily with 

 it in aqueous solution, i gm. of sugar absorbing about i mgm. of it. This 

 proportion is low, but can vary considerably. 



Glucose and fructose were compared as regards their power of com- 

 bining with sulphurous acid. Two solutions of 100 and 200 gms. per litre 

 of invert sugar and a 10 per cent solution of glucose were prepared by 

 allowing invertase from yeast juice to act at a temperature of 40° C. on 

 solutions of saccharose. Other 10 per cent and 20 per cent solutions of in- 

 vert sugar and 10 per cent solution of glucose were also made by dissolving 

 saccharose in a 0.3 per cent solution of hydrochloric acid at a temperature 

 of 80° C. On all these solution^ obtained by two methods, the effect was 

 tried of adding i mgm. and 2 mgms of sulphur dioxide. 



The results obtained after letting the solutions stand for 48 hours, 



all air being excluded, are given in Table I. 



i 



Table I. — Combination of sulphur dioxide with glucose 

 and invert sugar. 



From this experiment the following conclusions may be deduced ^ 

 Solutions of invert sugar and solutions of glucose prepared by yeast 

 juice combine with rhucji the same amount of sulphurous acid when they 

 each contain the same amount of glucose. But invert sugar obtained by 

 the action of hydrochloric acid and heat has a power of absorption double 

 that of gluco.se, for in this case the fructose acts too. 



