CONCENTEATION OF SALT SOLUTIONS. 



29 



The above sets of observations agree in showing that the excess of the density of 

 solutions of this salt over that of water at the same temperature is, for solutions which do 

 not contain more than about 25 per cent of anhydrous salt, directly proportional to the 

 percentage of anhydrous salt which they contain. 



Observer : Gerlach. ' 

 Temperature : 15°C. 

 Formula : Dj, = • 99915 + • 0091 267 p. 



Sodium Sulphate. — Na^ SO,. 



These experiments would seem to show that the above formula holds in the case of 

 Sodium Sulphate for solutions containing from to 4 per cent of anhydrous salt. The 

 following are other observations with the same salt : — 



Observer : Ostwald. ^ 



Temperature: 15°C. 



Formula : Dij = - 99915 + - 0091875 p. 



Thus Ostwald's experiments give the same result. 



Observer: Thomsen.^ 



Temperature: 18°C. 



Formula: Di8 = 0-99866 + 0-0093717p. 



Caustic Potash. — KHO. 



> Fres. Zeitscbr. f. analyt Chem., viii (1869) p. 279; and Landolt u. Bornstein's Phys.-chem. Tabellen (1883). 

 - Journ. f. prakt. Chemie xxii (1880) p. 305. '■' Thermo-chemische Untersuchungen, Bd. i, p. 47. 



