172 ANNUAL OF SCIENTIFIC DISCOVERY. 



to produce acids, appeared to me eminently proper to fulfil one of the 

 conditions mentioned, viz., to prevent by their presence the oxygen of 

 the air from acting in producing fermentation. 



" I have no doubt but that some one more capable than myself will 

 ultimately succeed in giving a practical form to the binoxide of azote, 

 for I cannot believe but that a substance which destroys instantly 

 oxygen, and forms with it an acid proper to precipitate the fermenting 

 matters, will be one day employed in the extraction of sugar. Dis- 

 solved in the sulphate of iron, it would guarantee the juice from all 

 alteration until the end of the purification by lime, and this accom- 

 plished, the juice would retain scarcely a trace of the reagents em- 

 ployed. 



" Aldehyde, or the organic substances which resemble it, are too 

 dear. I therefore made no stop at them. 



" During all the experiments which I slightly mention, I found my- 

 self always inclined to return to the use of sulphurous acid; its effi- 

 cacy as an obstacle to fermentation is so well proved, its price is so 

 low, its production so easy, and the substances necessary to produce 

 it so universal. It is true, that sulphurous acid, which was so suc- 

 cessful in the hands of Proust when used to prevent fermentation in 

 the saccharine matter of grapes, has always presented, when applied 

 to the manufacture of beet-sugar, insurmountable objections. I was 

 not ignorant, either, that the most experienced persons had failed in 

 the attempt to use it. Nothing practical had resulted from their 

 efforts. 



" If sulphurous acid can be profitably used where the must of grapes 

 is concerned, if in preventing fermentation it has no influence on the 

 sugar, it is because it possesses at once these properties either of 

 itself, or because it is converted into sulphuric acid by the action of 

 the air' Every one knows, on the contrary, that the cane-sugar is 

 changed, and takes the nature of grape-sugar, when placed in contact 

 with acids, particularly with sulphuric acid. Thus, however inoffen- 

 sive the sulphurous acid is when applied to the must of grapes, it is 

 impossible to use it for the juice of the sugar-cane or the beet; for 

 as soon as the air absorbed by the sulphurous acid changes it into 

 sulphuric acid, the effect of this last on the juices mentioned changes 

 them into grape-sugar. Reflecting on this difficulty, I asked myself 

 if sulphurous acid used with a powerful base such as potash, soda, 

 or lime, would still present this obstacle. I found, in reality, that 

 the base, absorbing the sulphuric acid as soon as formed, left the 

 sugar intact. From this point I was led to make many experiments, 

 easy to reproduce, useless to repeat in detail, and which I will sum 

 up in a few words. 



" Dissolved sulphurous acid added to a solution of the juice of sugar- 

 cane, or beets, prevents fermentation, but destroys slowly the sugar 

 if left cold in contact with the air. If heated, the destruction is much 

 more rapid. The neutral sulphites of potash, of soda, and of lime, 

 do not prevent fermentation, but do not injure the sugar, whether 

 cold or warm. Neither of these products, then, would serve. The 

 acid sulphites, and more especially the sulphite of lime, presented, on 



