1906-7.] 
Optical Rotation of Two Salts. 
III. Discussion of the Observations. 
279 
On examining figures 1, 3, and 4 it will be seen that an increase in 
the concentration of the molybdate salt produces an increase in the density, 
conductivity, rotation, and rotation-dispersion of the \ normal tartarate 
solution. Further, it will be noted that whereas these curves are in general 
concave to the concentration axis, for a short distance in the neighbourhood 
of concentration J they are in every case convex. Such unanimity is no 
doubt significant. 
Another point of interest is as follows. The original tartarate solution 
has its rotation-dispersion governed approximately by the simple law, 
(Rotation) x (Wave-length) 2 a constant. This is brought out in the 
subjoined table. There is also given there, for the sake of comparison, the 
figures obtained in a similar way for the other solutions, and it will be 
seen that the addition of the molybdate in general causes departure from 
the above law. It will be noted, however, that whereas the value of aX 2 
decreases with increase of X in the case of solutions ■(£), (J), and (f), it 
increases for solution (1). Hence there is probably some concentration 
lying between (f) and (1) for which the law once more holds. 
A 
Solution (0). 
E A 2 . 
Solution (D- 
E A 2 . 
Solution (!)• 
E A 2 . 
666 
1111 
3088 
5097 
598*5 
1087 
3066 
5136 
550-5 
1096 
3152 
5243 
515 
1091 
3217 
5398 
487 
1103 
3276 
5589 
455 
1064 
3451 
5983 
A 
Solution (D- 
E A 2 . 
Solution (|). 
E A 2 
Solution (1). 
E A 2 . 
666 
6704 
1377 
6229 
598-5 
6670 
1407 
5308 
550-5 
6910 
1458 
4774 
515 
7137 
1514 
4424 
487 
7454 
1594 
4203 
455 
7660 
1592 
c. 4024 
As regards the rotation dispersions plotted in figure 4, the convexity of 
all the curves near concentration (J) has already been pointed out. It is 
possible that the existence of a maximum in all the curves between (f) and 
