Evaporation and Dissociation. 



455 



Superior curve : 



a = 3'59797; log 6=1-8343195 ; log a = 0*00257762. 



Ordinary vapour-pressure : 



a = 6-72909; log 6 = 0-4027232 ; log a =1-99876897 



(b is here negative). 

 Inferior curve : 



a=4-867404; log 6=1-5913793 ; log u = 1-98382413 



{b is again negative). 

 In each case t = t° Cent. — 160°. 



The results are given in the following Table : — 



Table IX. 





Ordinary 



Superior 



Inferior 



Tempe- 



vapour-pressures. 



curve-pressures. 



curve-pressures. 



rature. 

















Bead. 



Calculated. 



Read. 



Calculated. 



Eead. 



Calculated. 



millim. 



millim. 



millim. 



millim. 



millim. 



millim. 



150 



13405 



13084 



17380 



17437 



-10400 



-10185 



160 



15900 



15900 



19090 



19090 



- 20 



- 100 



175 



20259 



20259 



22100 



22100 



+14060 



+14060 



185 



23703 



23678 



24510 



24549 



21660 



21704 



190 



25554 



25556 



25870 



25935 



24960 



24900 



192 



26350 



26341 



26490 



26523 



26125 



26065 



193 





26739 





26826 





26624 



193-83 





27075 





27077 





27077 



With exception of the lowest temperature, the agree- 

 ment between the read and the calculated pressures is close. 

 The extrapolation amounts to only 3°*83. The agreement 

 is close at 192°, and above that temperature the extrapolation 

 is only 1 0, 83. It will be seen that at that temperature 

 (193 G, 83) the pressures coincide. The apparent critical point 

 was 193°-8. 



Isoclioric Lines. 



Plate IX. represents the whole of the isochors which we 

 have calculated between the volumes of 1'85 and 300 cub. 

 centim. per gram. 



If the gas followed Boyle's and Gay-Lussac's laws abso- 

 lutely, under all conditions, the isochoric lines would all radiate 

 from zero pressure, and would become more and more vertical 

 as the volumes decreased ; and the tangents of the angles 

 formed by these lines with the horizontal line of zero pressure 



