114 ROYAL SOCIETY OF CANADA 
tions found to the law are as numerous as the agreements with it, 
but these are explained as due to incomplete dissociation, e.g., in the 
case of Ba, Sr, Ca, Mg, etc., salts. Entire agreement is only to be 
looked for at high dilution, and in the case of the Li, Na, K, and 
NH, salts. With one exception, however, the acids examined are 
possessed of a comparatively low rotatory power — never above 50°— 
and so the degree of dilution to which their change of molecular rota- 
tion can be accurately followed with any ordinary polarimeter is very 
limited — in fact, scarcely within the limits where agreement with the 
ionic theory would be expected. On this account, having prepared 
a quantity of active mandelic acid for other purposes, it seemed worth 
while to first employ it for this investigation, as it is a very active 
substance, having a molecular rotation of about 200°. 
The acid employed was the dextro modification, and it was 
obtained by fractional crystallization of the quinine salt of the inactive 
acid. It melted, sharp, at 132:5°, and had a specific rotation of 
+ 154-2° in 2 per cent solution at 17°. The salts were not prepared , 
in the free state but by neutralizing a weighed quantity of the acid 
by a standard solution of the hydroxide in the case of the sodium, 
potassium, and ammonium salts, and by the theoretical quantity of 
the pure carbonate in the others. This solution was then diluted to 
4 normal or + normal, and from these the various other concentrations 
were prepared by the use of calibrated pipettes and flasks. The results 
obtained for the molecular rotations of the various salts are contained 
in the following table. The observations were made at 15°. 










CONCENTRATION. |4N|/ 4 N/A4N/[ANIANIANIANIAN [xt N 
Metallic ion 
H. 7 a a ae & PAA) | 2S idea 77.010) Iloaas fe 220°0 | 221°5 
Li. 185°6 | 182°4 | 181°2 | 180°8 |....... 18220 PP EEERE PRE EEE 
Na. 1874]; 71} EL 2) 160; OMS eae .| 183-0 
K. 182°5 | 180°0 | 180°2 | 180°0 | 179°6 | 181°6 |....... jh... 
NH, LSU 18084 7S 018179010178 91182 0) PP PER) REP PNR EPS 
Ba: NM AIME 192:6 |) TOUR #189:01| 188;:6 || MS9IOM PEER IE CAE PIECERPR 
Sr. 1 110190211193 208101570187: TEE 189: 0.160,20) SEE 
CAN PALA RICE RAR 218°4 | 210°0 | 203 0 | 200°3 |....... 192 HA ATP aleneesters 
Mo ane al P RAS 198°0 | 194°4 | 191°0 | 190°5 |....... 0 KE) US Jol hae EN EEE 


An examination of the table shows that the molecular rotations 
of all the salts decrease with dilution, and, that in the case of Li. Na. 
