Law of Molecular Force. 

 C0 2 at 35°-5 C. 



131 



Y olume 



01368 



00196 



•00303 



•00263 



00235 



■002082 



•002073 



•002053 





Pressure, Andrews ... 



42-40 



60-54 



66-67 



80-96 











„ Araagat 



42-80 



61-00 



70-00 



91-00 



14.0 







320 



,, equation ... 



43-29 



53-34 



67-57 



106-80 



176 



314-5 



320 



338 





C0 2 at 6 ( 



D -9 C 



at 13° C. 





•07921 



•02589 



•01377 





Pressure, Andrews ... 

 ,, equation ... 



908 

 9-19 



23-35 



2386 



35-42 

 36 86 



It will be seen that the results of the two experimenters 

 for 100° agree well with one another, and that the equation 

 represents them satisfactorily ; and the same may be said of 

 the results for 64°, except that Andrews's pressure of 178 

 metres for volume '00277 is in remarkable disagreement with 

 Amagat's number 164. There is room for an error in my 

 correction of Andrews's air-manometer pressure ; but we see 

 that the error must be small, for the same pressure receiving 

 the same correction v>hen it corresponds to volume '00359 at 

 100° is brought into good harmony with Amagat's number 

 and with the equation. Thus we receive a first evidence of 

 the discrepancies to be encountered in a more formidable 

 manner when we study the numbers for 3f)°'5. Here, at 

 comparatively large volumes, the discrepancies between equa- 

 tion and experiment are sufficiently striking, but hardly more 

 startling than the difference between the two experimenters' 

 results. The magnitude of these differences perplexed me for 

 a long time, and I could assign or imagine no adequate cause 

 for them until, by the discovery that the usually assigned 

 critical temperature of C0 2 (31° C.) is too low by more than 

 10°, I was led to see that capillary action exercises a profound 

 disturbing action on the relations of pressure, volume, and 

 temperature of a fluid in the neighbourhood of the critical 

 state. As both Andrews's and Amagat's experiments were 

 conducted in capillary tubes, we can see in the difference of 

 their tubes a reason for the difference in their results. I may 

 mention that the serious discrepancies between the results of 

 the two experimenters and of the equation are confined to the 

 neighbourhood of the pressures for which pv is a minimum ; 



K2 



