267 



aid of fig. 1. The numbers given for the specific rotation [«J, are 

 the mean values of commonly three or four different values obtained 

 in various series of measurements ; they always relate to a content 

 of anhydrous salt in 100 weight-parts of the solution : 



From this it becomes evident that the solutions of the right-handed 

 salt are only dextrogyratory in reality, if green and yellow light- 



18* 



