Journal of the chemical society 1921/II. [antikvár]

J O U R N A L op THE CHEMICAL SOCIETY. ABSTRACTS OF CHEMICAL PAPERS PUBLISHED IN BRITISH AND FOREIGN JOURNALS. PART II. General and Physical Chemistry. The Molecular Refraction Coefficient, its Additivity Character and its Use for Determining Constitution. II. The Calculation of Refractive Indices of Aromatic Hydrocarbons. Fritz Eisenlohr (Ber., 1920, 53, [B], 2053-2063).- In a previons paper (A., 1920, ii, 717) it was pointed out that the " molecular coefficient of refraction/' M x is more sensitive to constitutive changes in the molecule than the generally employed "molecular refraction." A study of the aromatic hydrocarbons of the benzene series shows that the value of the coefficient depends on the relatíve positions of the substituting alkyl groups in the ring. The observed values exceed those calculated from the atomic values of the constituent atoms, after allowance has been made for ring formation, by an amount which is termed the E value. When the E values associated with a limited number of groupings are known, for example, twTo methyl groups in ortho-, meta-, or para-positions, three methyl groups in 1:2:4-positions, etc., it becomes possible to 'calculate the E value, and consequently the molecular coefficient of refraction and refractive index, of any hydrocarbon of the series. A number of typical examples of such calculations are given. E. II. R. The Dispersion of the Refraction of Hydrocarbons. E. Dabmois (Compt. rencl., 1920, 171, 952-955).-The specific dispersion of a substance is defined as being the ratio An/d, where VOL. CXX. ii. 1