84 K. D. Kraevitch on an Approximate Law of the 



I calculated y for three temperatures, 75°, 80°, and 85°, 

 taking the value of x the same in each case — 9*2657, and 

 took the mean of the results. I found 



y = 4205-3, 



r = 4205-3x4= 1 40'2. 



According to Berthelot, the heat of vaporization under the 

 ordinary pressure (175°?) is 120*1. 



2nd Method. 



t. 



P> 



dp 

 di' 



t. 



p. 



dp 

 dt' 



o 



60 



97-4 

 117-8 

 142-0 

 170-6 

 204-3 



5-260 

 7-324 



o 



85 



244-1 

 290-6 

 345-2 

 408-5 



8-597 

 10-077 



65 ;.. 



90 



70 



95 



75 



100 



80 







(TY) 



Each — is the arithmetical mean of two figures which do 



not agree very well together owing to the errors contained in 

 the pressures. Thus the differential coefficient for the pressure 



244*1 calculated as -|- 3 from pressures 170*6, 204*3, 244*1, 



and 290*6 proved equal to 8*611 ; and that calculated after the 



formula -J^ 2 from pressures 204*3, 244*1, 290*6, and 345*2 



equalled 8*583. Hence in the mean 8*597 an error may be 

 suspected in the two last ciphers ; which error should also 

 enter into the figure expressing the heat of vaporization. 



t 70° 75° 80° 85° 90° 



r 145-27 146-76 148-91 150-46 152-31 



-1-69 -2-15 -1-55 -1-85 



c-c x -0-338 -0-430 -0'310 -0-370 



The values of c — c 1 and of r found by the two methods differ 

 considerably. This indicates, as has been already said, the 

 insufficient accuracy of the observations on the vapour-pressure 

 of acetic acid. 



