Density, and Temperature of Salt Solutions. 291 



the calcium chloride series, but on plotting the curves as 

 shown, their appearance suggested an inquiry which led to 

 the following interesting discovery of a relation between 

 viscosity and density whioh does not appear hitherto to have 

 been noticed. 



In the Phil. Mag,"* Ramsay and Young published a law 

 connecting temperatures at which different saturated vapours 

 have the same vapour pressure. Porter, in the same 



T 



magazine f, showed that if r ^~ be plotted against T where T 



and T are temperatures of two liquids having the same 

 vapour pressure or the same viscosity at these temperatures, 

 then a straight line will be obtained. From this he deduced 

 that Ramsay and Young's law is accurately true if 



f(p) =A-^ 



or F(/a) = a — 7j. 



Porter showed the latter law to hold for two such dis- 

 similar substances as mercury and water. Now in the cases 

 given of sodium and calcium chloride it was found that if 



^- be plotted against /x where /* and /^ are viscosities at 



similiar densities, an approximate straight line was obtained, 

 indicating the relationship 



F00-A-5. ...... (i) 



In order to eliminate one of these constants this was thrown 

 into the form 



F( P -1)-A-? ( 2 ) 



When p = 1 we get B = p A, 



where /x' is the viscosity of water at temperature considered. 

 (2) then becomes 



fv-D-a(i-£). 



* Jan. 1886. t June 1907 and June 1912. 



U2 



