CH. V.] . SPECIFIC ROTATORY POWER. 147 



the information concerning the rotations of the sugars to 

 the mercury green. In all cases the final rotations are 

 given (see p. 103). 



WD [fl] Hg 



Glucose.. .. + 52'5 62 



Lactose hydrate .. + 52*4 61*9 



Lactose anhydride + 55*2 65*2 



Maltose . . . . + 138 163 



Sucrose . . . . + 66*5 78*5 



Fructose .. .. 93-8 - no'8 



d-Galactose .. + 81 95*7 



/-Xylose.. .. + 19 22*4 



Invert sugar .. .. 20-6 24*6 



For carbohydrates the [a] Hg can be obtained by 

 multiplying [a] D by 1*181. This relationship is not 

 necessarily true for substances whose molecular construc- 

 tion differs from that of the carbohydrates. 



F. Optical Activity and the Asymmetric Carbon Atom. 



If C be a carbon atom attached to a, b and x, different 

 atoms or groups, it is found that there exists only one 

 modification of the type Ca 2 bx. But if the structural 

 formula be written in one plane it would appear that two 

 arrangements are possible, viz. 



a a 



x a 



A B 



In A the groups a are adjacent, whilst in B they 

 apparently are separated. 



