204 Proceedings of the Royal Society of Edinburgh. [Sess. 
XI. — The Optical Rotation and Cryoscopic Behaviour of Sugars 
dissolved in (a) Formamide, (6) Water. Part II. By John 
Edwin Mackenzie and Sudhamoy Ghosh, D.Sc. (Edin.). Com- 
municated by Professor J. Walker, F.R.S. 
(MS. received December 8, 1915. Read January 10, 1916.) 
Introduction. 
In a recent communication ( Proc . Roy. Soc. Edin., 1914-15, vol. xxxv, 
p. 22) measurements of the optical rotation and cryoscopic behaviour of 
the following sugars, viz. /3-Z-arabinose, /-xylose, a-cZ-glucose, a-d- 
galactose, cZ-mannose, cZ-fructose, a- and /3-lactose, dissolved in (a) 
formamide, ( b ) water, were described. The investigation has been carried 
a step further by the addition of /3-cZ-glucose, /3-cZ-galactose and maltose 
to the above list. Thus the change in rotation or mutarotation in forma- 
mide solution has now been measured, starting from both the a- and 
ft- form of d-glucose, d-galactose and lactose. As in the case of the water 
solutions of these sugars, the constant rotation shown when there is 
equilibrium between the two modifications is found to be the same whether 
the starting-point be the a- or the ^-modification. 
The phenomenon of mutarotation having been demonstrated to be of 
similar character in non -aqueous and aqueous solutions, it is obvious that 
any explanation of the mechanism of mutarotation reactions must account 
for such reactions taking place in the absence of water. The theories 
hitherto set forth by various authors are mainly concerned with the change 
of rotation in aqueous solutions. It has been shown that in aqueous solu- 
tions the presence of even traces of alkali increases to an enormous extent 
the rate of mutarotation of sugars (cf. Lowry, Chem. Soc. J., 1899, lxxv, 
212). But the presence of alkali causes an enormous increase in the 
electrical conductivity of water and it has been assumed that the increase 
in the number of hydroxide ions is responsible for the increase both of 
electrical conductivity and rate of mutarotation. 
In the course of voluminous researches, Nef and others have theorised 
upon the changes undergone by sugars in presence of alkali and have 
come to the conclusion that, in aqueous alkaline solutions, sugars exist, 
at any 7 rate to some extent, in enolic modifications, e.g. glucose as 
CH(OH) : C(Ofi) . (CHOH) 8 . CH 2 OH; but it is very doubtful if 
