173 
1906-7.] Mixed Solutions of Optically-Active Substances. 
antipodes possessing different solubilities in optically-active media ; no such 
difference has yet been observed. Tolloczko * * * § shook up aqueous solution 
of racemic acid with active amyl alcohol, which is almost insoluble 
in water ; he observed no selective extraction of the one or other 
stereoisomer. Goldschmidt and Cooper j- determined the solubility of 
d- and of £-carvoxim in active limonen at various temperatures, and found 
identity of solubility in the two cases. Cooper f further determined the 
solubility of the ^-sodium hydrogen d- and ^-tartrates in c^-glucose solu- 
tions and found no differences in solubility. Quite recently H. 0. Jones § 
found that the solubilities of d- and of Gcamphor, and of d- and 
£-camphoroximes in purified turpentine (d-pinene) and in £-amyl bromide, 
were identical. 
Then, again, Emil Fischer l| was unable to detect any difference in the 
rate of inversion of cane sugar by d- and ^-camphoric acids. Caldwell f 
very carefully measured the rates of inversion of cane sugar by the 
/3-sulphonic acids of d- and ^-camphor, and found them to be the same. 
Unpublished measurements, made by one of us in conjunction with Mr T. 
Rettie, on the inversion of cane sugar by the tartaric acids lead to the same 
conclusion. 
In these instances it will be generally conceded that there is no definite 
chemical combination between the two . optically-active substances ; if it 
does exist, it is almost certainly not of the same character as that obtaining 
in the systems of the other class. 
There still remain two cases of special interest, as they do not belong 
with certainty to either of the two classes discussed above. Pasteur ** found 
that ammonium hydrogen c£-tartrate formed a well-defined crystalline 
substance with ammonium hydrogen £-malate, whereas ammonium hydrogen 
Gtartrate forms no such crystalline substance with ammonium hydrogen 
Gmalate. Other similar differences are also known in the case of 
derivatives of tartaric acid and malic acid. Whether this crystalline 
substance can be regarded as a chemical compound is doubtful, and it 
has been recently stated by Brunitt not to be a double salt but an 
isomorphous mixture. 
* Zeit. Phys. Ghem., 20, p. 412, 1896. 
t Zeit. Phys. Ghem ., 26, p. 711, 1898. 
J Amer. Ghem. Jour., 23, p. 253, 1900. 
§ Proc. Gam. Phil. Soc., 14, p. 27, 1907. 
|| Zeit. Physiol. Ghem., 26, p. 83, 1898. 
IT Proc. Roy. Soc., 74, p. 184, 1904. 
** Ann. Ghem. Phys. (3), 38, p. 461 1853. 
ft See MeyerhofFer, Gleichgewichte der Stereomeren , 1906, p. 62. 
