Evaporation and Dissociation. 



201 











































iOOO 2000 3000 4000 



important to show the truth of the equation p = bt—a for 

 liquids, we have decided, after due consideration, to re- 

 produce the isothermals exhibiting compressibility, inserting 

 crosses ( x ) to denote the pressures calculated by means of 

 the values of b and a given in the preceding Table. It will 

 be noticed that these crosses are often more in concordance 

 with the actual observations than are the lines drawn before 

 we had discovered this relation. These are shown on Plate III. 



Between volumes 3 and 12 cub. centim. per gram we give 

 a table of comparison (Table IV.). 



For higher volumes a comparison is made with the results 

 of actual experiment. The volume at the mean temperature 

 is given in each case, although at the extreme temperatures the 

 divergence in some cases amounts to 0*15 per cent. (Table V.) . 



The values of a and b given are the best available from the 

 determinations ; but as these are few at volumes near the 

 critical volume, the range of temperature being too small to 

 permit of ascertaining the values with accuracy, no great 

 dependence can be placed on them. This is proved by the 

 fact that at 220°, if the areas included between the vapour- 

 pressure line and the serpentine curve are made equal, the 

 vapour-pressure shows an error of about 3 per cent. We do 

 not regard this as in any way opposed to our conclusions ; 

 for while with ether about the critical volume, the range of 

 temperature from which the values of b and a were calculated 

 amounted to 55 degrees, and while at volumes slightly greater 

 measurements up to 85 degrees were made use of, with alcohol 

 the total range of temperature was only 3 degrees at corre- 

 sponding volumes. They cannot, therefore, have at all the 

 same claim to accuracy. 



Acetic Acid. — The data are given in the Trans. Chem. Soc. 

 1886, p. 790. As in the original paper we have omitted to state 

 the volumes of 1 gram, we give a Table (VI.) containing these 

 values. 



