Section q8. Summary. 281 



much with the concentration : some idea of its magnitude is furnished by 

 the following values which hold at about 0.01 molal (or 0.002 molal at 

 156) ; 18,500 X 10" G at 18, 1.220 X 10" at 100, and 115 X 10" at 156, 

 whereas the ionization-constant for acetic acid at 18 is 18 X 10'. From 

 the change of the ionization-constant with the temperature, the heat 

 absorbed (AU) by the reaction HS0 4 " = H + -f- S0 4 " has been found to be 

 given by the expression: AC/ = 1 1,170 65 T, where T represents the 

 absolute temperature. From this it follows that the value at 18 is 4,750 

 calories and at 100, - 10,070 calories, while from Thomsen's heat-of- 

 neutralization measurements and our ionization data the value - 5,020 

 calories is derived. 



