180 Proceedings of the Boyal Society of Edinburgh. [Sess. 
It is curious that the viscosity of the solutions show this difference so 
much more clearly than the density or the electric conductivity. Hitherto 
the differences observed between corresponding solutions of racemic and 
dextro- or laevo-compounds have been very small, and necessitated very 
accurate work. 
For example, Perkin * found that an 8*333 per cent, solution of tartaric 
acid had the density at 15°/15° C. of T03703, whilst the density of racemic 
acid of the same concentration was P03712. Again, Marchlewski f found 
that 14018 per cent, solutions of tartaric acid and of racemic acid had the 
densities at 15°/4° of 1*06600 and 1*06623 respectively. In dilute solutions 
these small differences entirely disappear. Ostwald found that the electric 
conductivities of tartaric acid and of racemic acid were the same, but the 
solutions were all dilute. Other examples are given in Meyerhoffer’s 
Gleichgewichte der Stereomeren, p. 20. 
In none of these instances are the differences so pronounced as we have 
found to be the case with the viscosities. It is somewhat surprising that 
there does not appear, in this instance, to be any close connection between 
viscosity and electric conductivity. During the course of the investigation 
it was noticed that the viscosity was affected by small traces of impurities 
in the substances, to a much greater extent than were the density or 
electric conductivity. 
In conclusion, as the addition of an independent optically-active sub- 
stance to solutions containing optically-active stereoisomers has not caused 
any recognisable differences, it would be of special interest to know if, in 
the other class, in which chemical combination undoubtedly occurs between 
the two optically-active substances, there are recognisable differences in 
the properties of the two compounds. Nothing appears to be known with 
certainty regarding these systems beyond the fact that, in general, the two 
compounds have different solubilities, and in one or two cases that the two 
compounds can form a partially-racemic compound. 
In continuing this investigation we intend to include an examination 
of solutions of typical substances comprised in these systems. 
We desire to express our thanks to the Carnegie Trust for a grant 
towards the expenses of this research. 
* Ghem. Soc. Jour., 51, p. 362, 1887. 
t Berl. Ber ., 25, p. 1561, 1892. 
Chemical Laboratory, 
University op Edinburgh. 
( Issued separately July 19, 1907.) 
