55'2 



Let us call i the degree of sorption (gr. of water per i gr. of 

 dry substance), and W the heat of sorption (generation of heat in 

 cal. when 1 gr. of dry substance absorbs 1 gr. of water). Then I found: 



This is the integral heat of sorption. From this 1 calculate the 

 differential heat of sorption for i = 



This value is considerablj' smaller than was found in swelling 

 substances (,250 to 400 cal.). At the heat of mixing of sulphuric 

 acid (with water) it amounted to 550 cal., of phosphoinis 100 cal., 

 of glycerine 20 cal. 



The curve of the integral sorption heats is graphed in fig. 1 ; it 

 starts as the ordinary curve of the heats of imbibition and of mixing, 

 as a hyperbola, then follows a flattened, almost rectilinearly rising 

 part, the end again being a hyperbola. Accordingly it is distinctly 

 ditïerent from the curves described by me formerly foi- bodies that 

 can swell up. 



I have not yet succeeded in calculating the differential sorption 

 heat in its full course from these measurements. The curve of the 

 integral sorption heat has so complicated a shape that a formula 

 with a great number of parameters is required to give any description 

 of it. The greater the number of parameters, the more arbitrary is 



