DEXTROSE. 207 



MOORE'S Test. If a dextrose solution is treated with about one 

 quarter of its volume of caustic potash or soda and warmed, the solution 

 becomes first yellow, then orange, yellowish brown, and lastly dark brown. 

 It has at the same time a faint odor of caramel, and this odor is more 

 pronounced on acidification. 1 



Dextrose forms several crystallizable combinations with NaCl, of 

 which the easiest to obtain is (C6Hi 2 O6) 2 .NaCl-f-H 2 O, which forms large 

 colorless six-sided double pyramids or rhomboids with 13.52 per cent 

 NaCl. 



Dextrose in neutral or very faintly acid (organic acid) solution under- 

 goes alcoholic fermentation with beer-yeast : C 6 H 12 O6 = 2C2H 5 .OH -f 2CO 2 . 

 In the presence of acid milk or cheese the dextrose undergoes lac tic - 

 acid fermentation, especially in the presence of a base such as ZnO or 

 CaCOs. The lactic acid may then further undergo butyric-acid fermenta- 

 tion: 2C 3 H 6 O3 = C 4 H 8 O 2 -f-2CO 2 + 4H. 



Dextrose reduces several metallic oxides, such as copper, bismuth, 

 and mercuric oxide, in alkaline solutions, and the most important 

 reactions for sugar are based on this fact. 2 



TROMMER'S test is based on the property that dextrose possesses of 

 reducing cupric hydroxide in alkaline solution into cuprous oxide. Treat 

 the dextrose solution with about -JJ vol. caustic soda and then carefully 

 add a dilute copper-sulphate solution. The (fupric hydroxide is thereby 

 dissolved, forming a beautiful blue solution, and the addition of copper 

 sulphate is continued until a very small amount of hydroxide remains 

 undissolved in the liquid. This is now warmed, and a yellow hydrated 

 suboxide or red suboxide separates even below the boiling temperature. 

 If too little copper salt has been added, the test will be yellowish brown 

 in color, as in MOORE'S test; but if an excess of copper salt has been added, 

 the excess of hydroxide is converted on boiling into a dark-brown hydrate 

 which interferes with the test. To prevent these difficulties the so- 

 called FEHLING'S solution may be employed. This solution is obtained 

 by mixing just before use equal volumes of an alkaline solution of Rochelle 

 salt and a copper-sulphate solution (173 grams Rochelle salt and about 

 50-60 grams NaOH per liter and 34.65 grams crystalline copper sulphate 

 per liter.) This solution is not reduced or noticeably changed by boiling. 

 The tartrate holds the excess of cupric hydroxide in solution, and an excess 

 of the reagent does not interfere in the performance of the test. In 

 the presence of sugar this solution is reduced. 



1 In regard to the products formed in this reaction, see Framm, Pfliiger's Arch., 64; 

 Neff, Annal. d. Chem. u. Pharm., 357; Buchner and Meissenheimer, Ber. d. d. chem. 

 Gesellsch., 39; Meissenheimer, ibid., 41. 



2 In regard to the products produced see Neff, Annal. d. Chem. u. Pharm., 357. 



