THE 

 LONDON, EDINBURGH, and DUBLIN 



PHILOSOPHICAL MAGAZINE 



AND 



JOURNAL OF SCIENCE. 



[FIFTH SERIES.] 



OCTOBER 1895. 



XXVIII. The Gladstone " Law " in Physical Optics, and the 

 True Volume of Liquid Matter. By Walter Hibbert, 

 FJ.C.* 



ONE of the curious results established in Chemical Optics 

 is that two independent formulse (those of Gladstone 

 and Lorentz respectively) can be used in the discussion of 

 experimental data relating to the refractive index and the 

 density of a given substance. Neither of them can claim any 

 special advantage. They both have a wide range of applica- 

 tion, yet neither holds universally good. Still more curiously, 

 they break down under quite different conditions of expe- 

 riment. 



The Lorentz formula, 



u? — l I 



£-s — ~ . t = constant, 



fi 2 + 2 d ' 



which is able to cover the large variation in density separating 

 a liquid and its vapour, gives erroneous results in the simple 

 case of a liquid whose density is changed by pressure. On 

 the other hand, the Gladstone formula, 



d 



= constant, 



is unique in its power to deal with liquids under varying 

 pressure, but fails in the jump from liquid to vapour. 



* Communicated "by the Physical Society. 

 Phil. Mag. S. 5. Vol. 40. No. 245. Oct. 1895. Z 



