J. C. Draper — Effect of Temperature on the 



Art. lY.— Effect of Temperature on the Power of Solutions of 

 Quinine to rotate Polarized Light. The corrections to he applied 

 for the same. Suggestions regarding the preparation to he used 

 when Quinine is employed as a Medicine; by JoHN C. 

 Draper, Professor of Natural History, College of tiie City 

 of New York. 



Lsr an admirable article on " The Action of the Solution of 

 certain Substances on Polarized Light," by 0. Hesse, in the 

 Annalen der Ohemie for 1875, the writer after dealing at length 

 with the varying action of the alkaloids on a beam of polarized 

 light says : " If we now take into consideration the fact that 

 transparent bodies, as water and alcohol, are able, under the 

 influence of electro-magnetism to deflect the plane of polarized 

 light, although this property does not otherwise belong to them; 

 and that the optical powers of a substance can be influenced by 

 mere mechanical means, as Scheibler has proved in certain 

 kinds of glass ; we must admit, that ' There is no real relat>on 

 between the rotating power of a substance and its molecules.' " He 

 then adds, " The rotating power of a substance is simply the 

 result of the variable action of its factors, viz: the arrangement 

 of the molecules as regards the volume, the solvent, the 

 temperature, the concentration, the chemical combination, the 

 dissociation and other things." 



The importance of utilizing the rotation power of quinine 

 for the practical purposes of analysis has induced me to en- 

 deavor to determine, as far as possible, the corrections to be 



pplied for the variations in question, and especially for those 

 dependent on temperature. Concerning this, A. Bouchardat 

 says, " variation in temperature causes variation in the rotation 

 power of quinine." In the paper mentioned above, O. Hesse 

 says, " in the case of Thebaine and Quinine the rotation dimin- 

 ishes under an increase of temperature;" but he afterward adds, 

 "I found that the variation between 15° C. and 25° C. was 

 insignificant." 



In my experiments the polariscope employed belonged to my 

 friend, Dr. K. A. Witthaus. It was made by Laurent, of Paris, 

 and read by verniers to two minutes. The tube was of glass 

 220 millimeters in length, with a lateral aperture near the cen- 

 ter, through which a thermometer was introduced for the deter- 

 mination of temperature. Around this tube I placed a water 

 jacket, the temperature of which was easily raised to and kept 

 at any required degree, by the injection of steam through a pipe 

 which passed to the bottom of the jacket. Having satisfied 

 myself by a series of experiments that extreme variations of 

 temperature in the water of the jacket, or bath, did not produce 



