Power of Solutions of Quinine to rotate Polarized Light 43 



any appreciable effect upon the indications of the instrumem 

 itself, 1 proceeded to the determination of the rotation power oJ 

 the purest sample of quinine I could procure. 



Bearing in mind the statement quoted above, that the con 

 centration, solvent and chemical combination have their in 

 fluenceon the amount of rotation, I assumed specific conditions 

 for the preparation of the experimental solutions which migh: 

 be easily reproduced. They were, 1st, the use of the uncom 

 bined alkaloid quinine, carefully dried over strong sulphuric 

 acid, 2d, ninety-seven per cent alcohol as the solvent and a 

 concentration proportion of one gram of quinine, to fifty cubic 

 centimeters of the alcoholic solution. For the sake ol' con- 

 venience the factors required in calculating the results are 

 presented in the following tabular arrangement, viz : 



V. volume of 97 p. c. alcoholic solution=50 cubic centimeters. 



p. weight of quinine = 1 gram. 



A. length of tube =220 millimeters. 



«= angle of rotation observed with sodium flame. 



The formula being [a-] y =^—^X 100 and the average of 200 

 observations on four solutions at a temperature ol 25° C. 

 being «= —6 -789° we have 



(1) 220X1 



[a]y = -154-30°at26°C. 

 Raising the temperature to 47° C. the average of 200 

 observations on the same solutions as before was «= —6 245° 

 from which by the formula we have 

 -6245°X50 ^ 

 ^2) ^""^^^ 220X1 ^^^^^' 

 [«]y=._141-93°at47°C. 

 The difference of temperature in (1) and (2) being 22° C. 

 and the difference in the angle of rotation 12 37°, it follows that 

 1° C.= -562° difference. 



That is, in a solution of quinine of the strength in question, 

 viz : 20 milligrams of alkaloid to one cubic centimeter of 

 alcoholic solution, for each additional degree Centigrade of 

 temperature the angle of rotation diminishes -562 of a degree. 



To ensure the correctness of these figures I caused my assis- 

 tant, Mr. Ivan Sickels, also to carry out a series of exjieriments, 

 and the result of seven hundred observations at temperatures 

 between 25° C. and 47° C. gave figures which only difiered in 

 the third decimal place. We are therefore justified in employ- 

 ing the correction in question for values in the vicinity of 25° 



