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

 2nd Method. 



t. 



p. 



djo 



di' 



t. 



p. 



dp 



di' 



260 , 



270 



- 

 280 



290 



96-88* 

 12301 

 155-17 

 191-46 



3-5524 

 4-3263 



300 

 310 

 320 



242-15 

 299-09 

 368-73 



5-2357 



* The tables give 73 ; if this value be left it gives certain irregularities. 

 In my opinion it should be 88. 



The last two figures of the differential coefficient contain 



errors. 



t 280° 290° 300° 



r 70-010 70520 70-990 



-0-516 -0-470 

 c-cy -0-0516 -0-0470 



The arithmetical mean for c— c x is equal to — 0*0493; and 

 r Q = 70*52. Both values are equal to those which were ob- 

 tained by the first method. Besides which we see that here 

 the heat of vaporization increases with a rise of temperature, 

 and that the quantity c — c x has a negative value, as was 

 found by the other method. 



t 



Pressures. 



t. 



Pressures. 



Calculated. 



Observed. 



Calculated. 



Observed . 



o 







80 



160 ... 

 220 ... 

 280 ..... 



0-002 

 0-203 

 5-33 

 34'20 

 154-96 



0-020 

 0-353 

 5-90 

 34-70 

 155-17 



o 



300 

 320 



360 . 

 420 . 

 520 



242-44 

 370-19 

 809-00 

 2281-8 

 9734-2 



242-15 

 368-73 



797-74 

 2177-5 

 8265-0 



23. The vapour-pressures of the acids C n H 2 n0 2 , formic, 

 acetic, propionic, butyric, and isovaleric, were measured by 

 Landolt, but unfortunately with considerable errors. Thus, 

 in the case of propionic acid, he gives a vapour-pressure 389' 

 for 120° and 650*2 for 135°, both of which figures are, without 

 doubt, wrong. It is scarcely possible to deal with these 



