158 



E. I. RosenUum 



This has been confirmed for the terpenes used in the present 

 research, and since the n-l/d figures approach more closely to 

 constancy than those based on tlie other two formula?,, they have 

 been adopted for comparing the molecular refractive powers. 



The constants are calculated by the three formulae for cineol, 

 1-phellandrene and 1-pinene are shown in a table, and the values 

 of «- l/c?x M are shown for all tlie substances, plotted against the 

 temperatures. 



These curves do not show much agreement with one another, the 

 greatest deviations being, as usual, shown by 1-phellandrene; but 

 it will be seen that the influence of temperature, though small, is 

 regular, and gives smooth curves. 



Eisenlohri has recently obtained as accurately as possible a series 



Refractive Indices. 



Eepbactive powers by various formulae. 



1 Zeit. Fhysik. Oieni., 1011, 75, 58;"). 



