M. Linnemann on the Conversion of Sugar into Mannite. 307 



begins to distil, for only at this temperature does it unite with, 

 the sodium ; otherwise, on afterwards cooling, the two metals 

 are found quite separate. The alloy may be kept in a stoppered 

 vessel for a long time without change. 



One part of this, and 1^ parts of iodide of ethyle, are placed 

 in a flask connected with a Liebig's condenser one end of which 

 dips in niercury,°and also with a carbonic-acid apparatus. When 

 the apparatus is full of carbonic acid, the flask is gently warmed in 

 the water-bath. After a few hours the reaction is terminated, and 

 it is only necessary to distil off and rectify the zincethyle, 

 which can be done by slightly modifying the apparatus itself. 

 The product obtained is almost the theoretical quantity, although 

 gases are disengaged during the operation, which bubble through 

 the mercury. The advantages of the method consist in its cer- 

 tainty and entire freedom from danger. 



Malic acid, fumaric acid, and maleic acid, by fermentation with 

 cheese, pass^ into succinic acid : the formation of this acid from 

 malic acid depends on a withdrawal of oxygen ; the formation 

 from fumaric and maleic on an addition of hydrogen. In most 

 cases of fermentation, this addition of hydrogen or withdrawal of 

 oxygen is so frequent that these actions are well called reducing. 

 Since the reduction of malic acid to succinic by Dessaignes and by 

 Schmidt*, and the formation of this latter acid from maleic and 

 fumaric f by Kekule, no doubt can exist as to the mode of for- 

 mation of succinic acid in the above cases. Sugar bears the 

 same relation to mannite that fumaric does to succinic acid. 



Fumaric acid. Succinic acid. 



€ 4 H 4 04 + H2 = Q4 H 6 04 < 



Sugar. Mannite. 



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



And Linnemann J, adding hydrogen to sugar, has changed it 

 into mannite. For this change, cane-sugar which has been 

 modified by treatment with dilute sulphuric acid is best fitted. 

 A strong solution of this was made, free from acid, and small 

 quantities of sodium-amalgam were gradually added. As soon as 

 the liquid was alkaline, the disengagement of gas ceased ; much 

 heat was disengaged, and the vessel required to be cooled. When 

 the action was complete, the liquid was acidulated with sulphuric 

 acid, the excess of acid neutralized with chalk, the sulphate of 

 lime removed by evaporation, crystallization, and the addition of 

 alcohol to the mother-liquor. The liquid was evaporated to a 

 syrup, from which, after long standing, the mannite separated 

 in crystals, which both by analysis and by its general properties 



* Phil. Mag. vol. xx. p. 49. f Ibid. vol. xxii. p. 306. 



X Liehig' sAnnakn, July 1862. 



