Power of Solutions of Quinine to rotate Polarized Light. 45 



In the 1st solution (6)^=1 • •v=bQ - -1 = 220 ■ ■ a=-5'5S° at 29° C. 

 In the 2d solution {1)p= 1 • • -y^lOO • • A=220 • • a=L~2-40° at 31° C. 

 In the3dsolution(8)j?>=il . •wi=200. ./^=220- .a=- I-IV" at35° C. 



By the formula [a]y==^-XlOO we have 



For (6) Mi =— 22^°^ X 100— 126-82° at 29° C. 

 For (7) M j - ^^o°^i— X 100= -109-09^ at 31° C. 

 For (8) Mi = =^^-^y^\l00=^ at 35° C. 



Here again we perceive that the effect of dilution is to 

 diminish the power of rotation, and to about the same extent 

 and in the same manner as in my series of observations. It is 

 therefore evident, that to secure results suitable for a reliable 

 comparison, the solutions of quinine employed should be as 

 nearly as possible of the same strength. The" proportion which 

 according to my experience it is most desirable to use is that 

 of about one gram of alkaloid to 50 cubic centimeters of 

 alcoholic solution. While a greater strength than this does not 

 present any advantage in a tube of 220 millimeters, it is objec- 

 tionable on account of its obstructing the passage of the light. 



Quinine combined with Sulphuric Acid. — For the examina- 

 this compound of quinine I prepared a solution 

 which held the^ same proportion of quinine alkaloid in a 

 that contained in the alco- 

 made by taking one gram 

 of dried quinine, dropping it into about 30 cubic centimeters 

 of distilled water, and adding just sufficient sulphuric acid 

 to dissolve it* The quantitv was then made up to 50 

 centimeters with distilled water, and the 220 millimeter tube 

 filled therewith. 



At a temperature of 21° C. the average rotation as deter- 

 mined by 100 observations was —11-36°. By the formula 



(9) [«]y = -^^^^XlOO=-258-18° at 21° C. 



The temperature of the solution in the tube was then raised 

 bv means of the water jacket, and the average of 100 observa- 

 tions was «=- 10-73° at 43° C. By the formula 



(10) Wy^3J^l^A<>xioo=-- 243-86° at 43° C. 



* Tliia solution was employed as being similar to that used by physicians. 



which held the same pro] 

 given portion of the soluti 

 holic solution. The soluti 



