Separation of Miscible Liquids by Distillation. 633 



is however approached quite slowly, as is evident from an 

 inspection of fig. 7. 



To facilitate the calculation of E , the ratio R /R<zc has 

 been plotted in fig. 5. R<z denotes, of course, the d.c. 

 resistance of the wire. For values of the argument b>b, 



R /JU<^/(2v / 2-2/&), 



which makes the calculation very simple. 

 April 17th, 1920. 



LV. The Separation of Miscible Liquids by Distillation. 

 By A. F. Dufton, B.A., Frecheville Research Fellow, 

 Royal School of Mines *. 



1. TN the search for a perfect apparatus for the separation 



JL of mixtures by distillation the greatest advances have 

 been made in industrial practice. M. Sorel, one of the 

 leading French authorities upon the distillation and the recti- 

 fication of alcohol, in reviewing the principles underlying 

 the construction of stills, writes : — 



" La plus grande partie des donnees dont nous avons 

 besoiu peuvent etre determinees dans la laboratoire du 

 physicien. Malheureusement bien peu de savnnts s'en sont 

 occupes, soit que le sujet leur parut peu important, soil que 

 Pimpossibilite jusqu'ici reconnue d'arriver a des lois mathe- 

 matiques les ait rebutes. II faut done que le constructeur se 

 transforme en experimentateur. . " 



" C'est l'aveu franc et net/'' to quote M. Chenard f, " d'un 

 empirisme certain/'' 



The extent to which laboratory practice has been out- 

 stripped may be seen by comparing the still designed by 

 Coft'ey J, of Dublin, in 1832, or Derosne's still, which give 

 in continuous distillation on the large scnle the strongest 

 spirit which can be obtained, with the various laboratory 

 still-heads examined by Dr. Young § in J 899. The only 

 continuous laboratory still appears to be an experimental one 

 do vised by Lord Rayleigh ||, which consisted of a long length 

 (12 metres) of copper tubing 15 mm. in diameter, and a 

 similar one described by OarvethH". 



* Communicated by Sir E. Rutherford, F.R.S. 



t Chenard, Bulletin de V Association des Chimistes de Sucrerie et de 

 Distillerie de France, 1915. 



% ' Chemistry as applied to the Arts and Manufactures. 1 "\ ol. 1. 

 Alcohol. 



§ Young, Journ. Chem. Soc. 1892, p. 679. 



i| Rayleigh- Phil. Mag-. (4) 1902, p. 536. 



f Carveth, J. Phys. Chem. vi. p. 253 (1902). 



