184 Proceedings of Royal Society of Edinburgh. [sess. 
crease of the k of -COOH by its change into -COOM brings it 
above the k of -CH 3 , and changes the order of the radicals. If this 
H H 0 
i i 11 
be so, then of the three radicals — C — H , — C — 0 — H , — C — OH , 
H H 
the k is greatest in the second and least in the third, so that the re- 
placement of H by OH raises the value of k, the replacement of 
H 2 by O lowers it, and lowers it more than the replacement of H by 
OH raises it. 
There is one set of cases to which we cannot as yet apply the 
method ; viz., where the asymmetric carbon atom forms part of a 
ring, as in diacetyl-tartaric anhydride, asparagine (if we regard it as 
a salt with twice the formula given above), camphor, &c. 
Of course we cannot as yet even approximate to a formula for the 
amount of rotation in terms of the four k’s and temperature, but as 
the rotation becomes zero when any two k’s become equal we may 
presume that it contains the product of the differences of the k’s. 
The first thing to be done with this speculation is to find whether 
k is really a function of the composition and constitution of the 
radical and of the temperature of the substance, or varies with the 
character of the other three radicals. This will require the prepara- 
tion and careful examination of many active substances and their 
derivatives. 
June 21 , 1890 . 
■ 
Since the paper of which the above is an abstract was read to the 
Society I have seen a note on the same subject by Mr Philippe A. 
Guye, published in the Comptes Rendus for March 31st of this year. 
There is a good deal common to Mr Guye’s view and mine, and I 
take this opportunity of acknowledging his priority in the points 
which are common. 
The chief difference is that Mr Guye regards the mass of each 
radical and the distance of its centre of gravity from the centre of 
figure of the tetrahedron as all that has to be considered as deter- 
mining the amount of asymmetry, whereas I suppose k to be a 
function of the composition and constitution of the radical, not 
necessarily proportional to the mass and the distance of the centre 
of gravity from the centre of the tetrahedron, so that, for example, 
