44 J. a Draper— Effect of Temperature on the 



C. which closely approaches the temperature at which such 

 observations are made in actual practical work. 



Effect of variation in the Proportion of Alcohol in the Solution.— 

 Hesse having shown that the strength of the alcohol has a 

 marked effect on the rotating power of quinine, it followed 

 that perhaps variation in the proportion of quinine dissolved in 

 a given specimen of alcohol would also give variation in the 

 power of rotation. In the examination of this problem I em- 

 ployed a freshly prepared solution of one gram of undried 

 quinine in 50 cubic centimeters of 97 per cent alcohol. The 

 average of 100 readings of the angle of rotation at various 

 temperatures from 20° C. to 50° C. was 



(3) «=-6-05°at35°a 



To the above 60 cubic centimeter solution 50 cubic centime- 

 ters of the same alcohol were added, forming a solution of half 

 the strength of the first solution. The average of 100 read- 

 ings at similar temperatures was 



(4) «=-2-61°at36°C. 



To this second solution an equal volume of alcohol viz : 100 

 c. c. was added, giving a solution of one quarter the strength 

 of the first. The average of 100 similar readings was 



(5) «=-l-27°at36°C. 



In the first solution (3) p = i and v= 50 

 In the second solution (4)^=1 and v=100 

 In the third solution (5) /) = 1 and i;=200 



By the formula [t^]y = ^Xl00 we have 



For (3) Wi=^=^f-\l00=-137-50° at 35° C. 



For (5) [«]/ = —220")^f-X 100= -115-45° at 36° C. 



From the above experiments w 

 dilution by alcohol of the soluti^ 

 power of rotation, and as far as th 

 ducted this effect is more marked 

 than in the second. 



The repetition of these experiments bv Dr. R. A. Witthaus 

 and Mr. Sickels. on a similar series of solutions made with the 

 same alcohol and an undried specimen of quinine, gave the 

 following averages of many hunclred readings. 



