§ 208. ESTIMATION BY POLARIZATION. 221 



is about the same as that of invert-sugar, so that after inversion 

 10 cc. of Fehling indicate about 0'0475 gram milk-sugar. i 



To Maltose, produced together with dextrin by the action of 

 diastase on starch, Schulze^ assigns the formula Gi2H220i^-|-H20. 

 It resembles milk-sugar in its behaviour to alkahne copper solution. 

 Boiling with dilute acids converts it entirely into dextrose, and, as 

 with milk-sugar, it is advisable to invert maltose before estimating 

 it with Fehling's solution. Its rotatory power is greater than 

 than that of dextrose ; {a)o - 149-5 - 150-6°. Maltose is said to be 

 (? directly) fermentable. With nitric acid it yields no mucic acid. 



MelUose crystallizes in needles containing 3 molecules of water. 

 It is soluble in 9 parts of cold water, and is dextro-rotatory 

 (-1-102°). Boiling with dilute acids converts it into glucpse and 

 eucalyn, the latter of which is not fermentable. Yeast also acts 

 in a 'similar manner (§ 206), in which case the glucose produced 

 ferments. With nitric acid melitose jrields abundance of mucic acid. 



Melezitose crystallizes in rhombic prisms with 1 molecule of 

 wajter of crystallization. It is freely soluble in water, insoluble 

 in alcohol and in ether. An aqueous solution is dextro-rotatory 

 (94-48°), and indifferent to Fehling's solution ; it is converted into 

 glucose when boiled with a dilute ac^d ; yields with nitric acid 

 no mucic acid, and is slowly decomposed by yeast. 



Mycose {trehalose) forms rhombic prisms containing 2 molecules 

 of water. Boiling spirit dissolves it tolerably freely ; in aqueous 

 solution it is powerfully dextro-rotatory (-f-220°), only slowly 

 and incompletely fermented by yeast, and converted into dextrose 

 when boiled with dilute acid for several hours. It does not 

 reduce copper solution, and yields no mucic acid with nitric acid. 



§ 208. Estimation by Folarization. — This is possible when the 

 glucose or saccharose is not accompanied by- any other similar 

 fcarbohydrate, and when the. solution contains no other substance 

 (asparagine, etc.) that has an action on polarized light, or when 

 all such substances present can be completely removed, either by 

 boiling (as albumen), or by precipitation with basic acetate of 

 lead (organic acids, gum, etc.) '(§ 210). Of course the rotation- 



1 Compare Eodewald and Tollens, Ber. d. d. chem. Ges. xi. 2076, 1878 

 (Year-book Phann. 77, 1879). 



2 Ber. d. d. chem. Ges. vii. 1047, 1874 (Year-book Pharm. 85, 1875), and 

 Jonm. f. Landwirthschaft, xxvi. 67, 1878. Seealso O'SuUivan, Monitear scient. 

 March, 1874 ; and Ber. d. d. chem. Ges. ix. 281, 1876 (Joum. Chem. Soc). 



