346 Mr. J. Dewar on Inverted Suga?\ 



the views entertained by the different parties to this discussion, 

 the author has thought some observations on the same subject 

 might not be unworthy of notice at the present time. 



Linneman, many years ago, applied the process of hydrogena- 

 tion to the sugars that had been found so successful in treating 

 the simpler organic substances. In this way he obtained man- 

 nite from inverted sugar, the following reaction taking place : — 



C 6 H 12 6 +H 2 = C 6 H 14 6 . 



Mannite had long been known to be the product of certain kinds 

 of fermentation, and to occur as a secondary product in the 

 vinous fermentation ; but it was this elegant synthesis of Linne- 

 man that first clearly showed the connexion. But although 

 inverted sugar can be changed into mannite, the next point that 

 demands a solution is, supposing the inverted sugar to be 

 composed of equal quantities of dextrose and lsevulose, are they 

 both transformed by hydrogenation into mannite ? or is only one 

 of them, and which ? Linneman seems to have directed his 

 attention to the solution of this question. He states that it is 

 only the lsevulose that is so affected. The reason why he 

 entertains the above view is not given. In all likelihood he 

 thought that, just as Berthelot had changed mannite by a pecu- 

 liar fermentation into lsevo-glucose, so would the lsevo-glucose in 

 inverted sugar be hydrogenized into mannite. 



In repeating the action of sodium-amalgam on inverted sugar, 

 I have not seen any reason why the one sugar any more than the 

 other should be supposed to generate the mannite. The follow- 

 ing is a description of the mode by which the sugar was inverted 

 and hydrogenized : — 20 grms. of cane-sugar were dissolved in 

 150 grms. of water, and inverted through the action of 2 grms. 

 of sulphuric acid, keeping the solution at the temperature of 

 70° C, afterwards adding pure carbonate of barium, filtering, 

 and then adding 12 grms. of sodium in the form of a weak amal- 

 gam. The action took place without any evolution of hydrogen. 

 If the amalgam was impure, from the presence of other metals, 

 it evolved hydrogen at once, and the solution became brown ; 

 otherwise it remained perfectly clear. After one month the so- 

 lution gave no trace of sugar with the alkaline copper solution. 

 It was then carefully neutralized with dilute sulphuric acid, eva- 

 porated on the water-bath, the greater part of the sulphate of 

 sodium separated by crystallization, and the residue treated with 

 boiling 70-per-cent. alcohol, the solution filtered and allowed to 

 crystallize. Sometimes the mannite did not crystallize until all 

 the alcohol had evaporated, leaving a syrup that slowly assumed 

 the crystalline form. The product had no rotatory power. In 

 no case was the sugar entirely changed into mannite; a gummy 



