24 THE ROYAL SOCIETY OF CANADA 
mined by his own experiments. This table shows a steady fall in 
the amount of nicotine corresponding to one minute of angular 
rotation, the determination being made upon solutions ranging in 
strength from 4-00% to 0-25%. 
Pribram (Ber. deut. Chem. Ges. 20-1840) states that the diminu- 
tion in the rotatory power of aqueous nicotine solutions is irregular, 
and does not decrease in proportion to the dilution. The irregularity 
seems most marked, according to his statements, at concentrations 
between 4% and 0-8%. 
On the other hand J. A. Emery (Jour. Amer. Chem. Soc. 26-1113) 
found the rotatory power of aqueous nicotine solutions to be propor- 
tional to the concentration between 1-2% and 0-4%, but his state- 
ment rests on only two determinations. 
We consider that our own experiments show that, within the 
range of accuracy of our instrument and for concentrations between 
4-0% and 0-37%, the rotatory power of an aqueous solution of nico- 
tine is strictly proportional to its concentration. 
We thus find ourselves in agreement with J. A. Emery, who 
appears to have used the same type of instrument that we did. It 
is possible, though hardly likely, that the irregularities found by 
Pribram and Popovici are connected with the wave length of the light 
used. The last mentioned observer gives no clue to the method 
he employed for determining the nicotine concentration of his solutions. 
If this was done by titration the results would necessarily be inexact. 
Our experiments also show, as we anticipated would be the 
case, that repeated evaporation with sulphuric acid in small excess does 
not cause any change in the rotatory power of nicotine. The rotatory 
‘power of aqueous nicotine solutions is not affected by the presence 
of free caustic alkali or salts of the alkali metals. 
; We find that the rotatory power of nicotine in water is such 
that, examined in a 2 d.m. tube, 1 gramme of nicotine in 100 cb.c. 
of solution would give a negative rotation of 4-5 divisions on the 
Ventzke sugar scale for ‘‘j’’ light, or conversely, a negative rotation 
1 division corresponds to 0-2198 gramme of nicotine in 100 cb.c. 
According to Emery’s determination (Joc. cit.) of the same factor, 
rotation of 1 division =0-224 gramme of nicotine in 100 cb.c. In 
criticism of this figure it may be pointed out that it rests on only 
two determinations and that these, while based on the same principle 
as our own, were made on very much more dilute solutions (1-233% 
and 0-404%) than we employed. While Emery increases the probable 
accuracy of his polarimeter reading by using a 4 d.m. tube, this 
increase does not fully compensate for the diluteness of his solutions. » 
