Molecular Constitution of Isomeric Solutions. 289 



\~ 4 , <r 6 , <r 10 , cr 20 , o- 40 is given by the theory, but to find the 

 position of these points on the curves we require to know the 

 value of k. 



Since the triangle in my diagram is equilateral, the colour 

 represented by any point P within the triangle can be ex- 

 perimentally obtained in the following way : — Let a prismatic 

 spectrum fall on a diaphragm with three adjustable slits, 

 whose centres are at wave-lengths 631, 529, and 457. Make 

 the breadths of the slits proportional to the perpendiculars 

 drawn from P to the sides of the triangle. Then the three 

 spectral rays, when compounded by a lens, will produce the 

 colour P. The dispersion of Maxwell's spectrum is defined 

 by the wave-lengths I have given of the sixteen equidistant 

 points in his spectrum. In consequence, however, of indi- 

 vidual variations in the colour sensations great accuracy 

 would be thrown away. 



Hotel Buol, Davos, July 10th. 



'XXXVII. On the Molecular Constitution of Isomeric 

 Solutions 8>'c. By Dr. G. Gore, F.R.S* 



IN the present research, the " voltaic balance " has been 

 applied to the detection of differences of chemical con- 

 stitution of a pair of isomeric solutions ; and to detect mole- 

 cular and chemical changes in them, caused by heat, light, 

 lapse of time, order of mixture, degree of dilution of ingre- 

 dients, &c. 



According to the results of J. Thomsen's thermochemical 

 investigations, as described by P. Muir (' Principles of Che- 

 mistry/ 1884, pp. 434, 437), "when nitric acid and sodium 

 sulphate react in equivalent quantities in a dilute aqueous 

 solution, heat is absorbed ; but when sulphuric acid and 

 sodium nitrate react under similar conditions, heat is evolved. 

 But the final distribution of the base between the two acids 

 will be the same in both cases, and, moreover, this distribution 

 will be the same when equivalent quantities of the two acids 

 (sulphuric and nitric) and the base (soda) mutually react." 

 " When soda, nitric acid, and sulphuric acid mutually react 

 in equivalent quantities in a dilute aqueous solution, two 

 thirds of the soda combines with the nitric acid, and one third 

 with the sulphuric acid." " The final division of the base 

 between the two acids is the same whether the soda were 

 originally present as sulphate or nitrate." (See also ' Theories 



* Communicated by the Author. 



