XXVIII.— REFRACTIVE POWER OF THE HYDROCARBONS 



AND CHLORINE DERIVATIVES DESCRIBED IN 



THE PRECEDING PAPER. 



Bt Charles F. Mabeky and Edward J. Hudson. 



Presented October 14, 1896. 



"Within recent years the refractive power of the hydrocarbons and 

 their derivatives has received considerable attention by Briihl, Thomsen, 

 and others, and attempts have been made to draw conclusions based on 

 the relation between the index of refraction and density, to define struc- 

 tural relations. The experimental data have been obtained for the most 

 part from bodies with a limited number of carbon atoms, in which the 

 differences in refractive power are large. Independent of determina- 

 tions bearing on theoretical considerations, the refractive power of oils 

 and solutions has been accepted on practical grounds as a valuable 

 property for recognition and for determining degrees of purity. 



While it was not to be expected that the determination of refractive 

 power in hydrocarbons with such a large number of carbon atoms as 

 those contained in the higher portions of petroleum would be serviceable 

 in ascertaining the structure of individual hydrocarbons, the wide differ- 

 ences in specific gravity between unpnrified and purified distillates led 

 us to believe that similar differences should be observed in refractive 

 power. When subjected to experimental proof, these differences were 

 easily verified. 



The determinations of the angle of refraction were made in the latest 

 form of Pulfrich refractoraeter, made by Carl Zeiss, Jena, and the calcu- 

 lations of the index of refraction by the formula 1 = -y/^^ — sin^ I, in which 

 1 represents the index of refraction, iV^the angle of the prism, and / the 

 observed angle. The observations in this refractometer are rapidly made, 

 and the calculations are much simplified by the use of a table arranged by 



