( 515 ) 



those wliicli arc mentioned at 15^7 in lable 1 ; from whieli follows 

 that the accuracy of the values of p at 25^ derived from the equa- 

 tion of state is still of the same order as those which are calculated 

 at 15°,7. 



In table III the values of /; are given at temperatures of 15°,7, 

 20° and 25° C. for different volumes calculated from the equation of 

 slate with the constants mentioned in llie fifth column of table I. In 

 order to render the calculation of pressures possible also for other tcmpe- 



ratures, the calculated values of ^- are mentioned in the fifth colunm 



of table III. (p. 516). 



As unit of volume we have taken the normal volume, i. e. the 

 volume which the air would occupy at 0° C. and 1 atm. (0°, 45° N. B.). 



So it is possible to represent an isotherm for a large range of 

 densities, widi the aid of the equation of state and values for the 

 constants « and /?, differing little from the theoretical values. 



These differences will be chiefly determined, besides by syste- 

 matic errors of the observations, by 1^^- the non-spherical shape of 

 bi-atomic molecules, 2'^ the possibility of a simultaneous real 



diminution, which could then explain at the same time the slight 



op 

 variability of -— . 



In table V the influence for different densities of the three 

 terms of the correction formula for the b is rendered. In the fourth, 

 fifth and sixth column the values are given, with which the l>r, is 

 diminished in consequence of the correction terms with a, /? and y, 

 expressed in per cents of b^j ; in the seventh column the decrease 

 of b,j in consequence of the three terms together is given in percents 

 of b,;. In the eighth column the influence of the decrease of b,; on 

 the pressure is represented ; if we calculate the p from the equation 

 of state keeping b constant and equal to b^, then this p will be 

 greater than that cahnilated by means of the decreasing b. 



The difference between them is given in percents of ^>. With a 

 volume of 0,02 already the decrease of b will manifest itself in a 

 decrease of p- 



It appears that the application of several correction terms would 

 be desirable for the smallest of the volumes observed by Amagat. 

 For larger \'oliimes, however, they have no influence, and their 

 theoretical values still being unknown, I have thought that in this 

 case three terms would be sufficient. 



♦ Several observers (i. a. Kuenen, Quint) hax'e made use of the air- 

 isotherm, determined by Amagat as early as 1864, for pressures 



34 

 Proceedings Royal Acad. Amsterdam. Vol. VI. 



