Isometrics of Liquid Matter. 



359 



from 53° to 17°, without solidifying under the initial pressure. 

 Comparing figs. 9 and 10, the following slopes are found 

 for the respective isometrics : — 



Table XL — Observed Initial Slopes of the Isometrics. 





Ether. 



Alcohol. 



Thymol. 



Diphenyl- 

 amine. 



Para- 

 toluidine. 



JSot corrected for volume- 1 



changes of glass tube (fig. 9) J 



Corrected for volume-changes 1 



of glass tube (fig. 10) J 



° C./atm. 



r -ii4 



\-115 

 1 '116 



j -114 



° C./atm. 



1-095 



•095 

 •094 



° C./atm. 



•071 



•073 

 •072 



° C./atm. 



•063 



•065 

 065 



° C./atm. 

 •070 



}-072 



Initial temperature, 9 Q = 



17° 



30 atm. 



34° 



17° 

 50 atm. 



78° 



17° 



80 atm. 



233° 



53° 



68° 



(400) atm. 



310° 



54° 



68° 



(400) atm. 



198° 



43° 



Boiling-point — 



Melting-point — 





It is seen from this Table as well as Table IX., that the 

 correction for non-rigidity of the constant-volume tube does 

 not exceed 2 per cent. In most cases, and for pressures not 

 too high, it may be disregarded. 



The slopes thus obtained (Table XI.) have no absolute 

 value, since the data must vary with the initial volume under 

 consideration. Volume-measurements are beyond the scope 

 of the present paper. I may state, however, that a study of 

 the thermodynamic surfaces of liquids, by the aid of consecu- 

 tive isometrics, promises to be experimentally the most precise 

 (§ 27). 



If the change of curvature (figs. 9 and 10) above 1000 

 atmospheres were due to an unwarranted application of 

 Hooke's law in case of the gauge, the curvatures of all the 

 isometrics would change in somewhat similar ways at the 

 same pressure. This is not observed in the figures, where 

 each isometric is found to have an individual character. Tests 

 made with thymol at the close of the above work reproduced 

 the straight isometric very beautifully, showing that the 

 curves for diphenylamine and toluidine are not influenced by 

 marked gauge-errors (see Table VIII., end). 



43. A singularly curious inference is suggested on com- 

 paring the approximate isometrics of solid glass computed in 

 §§ 38, 39, with the liquid isometrics of Tables X. and XI. 

 For glass the initial slope of the isometric is about *1° per 

 atmosphere, a datum which comes very near (in order) to the 

 slopes of the liquid isometrics, varying as they do between 

 •07° per atm. and '12° per atm. This proximity of the solid 



