§ 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.^ 



To Maltose, produced together Avith dextrin by the action of 

 diastase on starch, Schulze^ assigns the formula CjoH^oO^^-fHgO. 

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

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

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

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

 than that of dextrose ; («)d = 149-5-150 -6°. Maltose is said to be 

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



Melitose crystallizes in needles containing .3 molecules of Avater. 

 It is soluble in 9 parts of cold AA^ater, and is dextro-rotatory 

 (-fl02°). Boihng Avith dilute acids couA^erts it into glucose and 

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

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

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



Melezitose crystallizes in rhombic prisms with 1 molecule of 

 Avater 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 AA'hen boiled Avith a dilute acid ; yields Avith nitric acid 

 no mucic acid, and is slowly decomposed by yeast. 



Mycose (trehalose) forms rhombic prisms containing 2 molecules 

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

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

 and incompletely fermented by yeast, and converted into dextrose 

 AA'hen boiled Avith dilute acid for several hours. It does not 

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



§ 208. Estimation hy Polarization. — This is possible Avhen the 

 glucose or saccharose is not accompanied by any other similar 

 carbohydrate, and Avhen the solution contains no other substance 

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

 all such substances present can be completely removed, either by 

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

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



^ Compare Eodewald and ToUens, Ber. d. d. chem. Ges. xi. 2076, 1878 

 (Year-book Pharm. 77, 1879). 



- Ber. d. d. chem. Ges. vii. 1017, 1874 (Year-book Pharm. 85, 1875), and 

 Journ. f. Landwirthschaft, xxvi. 67, 1878. See also O'Sullivan, Moniteur scient. 

 March, 1871 ; and Ber. d. d. chem. Ges. ix. 281, 1876 (Journ. Chem. Soc). 



