1885.] 



on the Heat of Dissolution of Salts. 



411 



Mean. 



Temperature. 

 16° . . 

 54 .. 



Heat of 

 dissolution. 



-4786 

 -4255 



Calculated from the values 0=21*8 (Kopp), 18rcK = 1791 

 (Thomsen), and taking Q^=-4786 at 16°, Q T =-3616 when T is 

 54°. 



The observed and calculated numbers for potassium sulphate and 

 nitrate and sodium nitrate are plotted out in the diagram below, 

 where it is manifest that there is a difference between the two 

 nitrates and the much less fusible and soluble sulphate. For tracing 

 up the abscissa for 45°, we see that the difference between the ob- 

 served and calculated numbers for potassium sulphate amounts to 

 upwards of 900 calories, whilst the corresponding difference in nitrate 

 of sodium is only about 500, and in nitrate of potassium about 



700. 



