Vapour-pressure and the Volumes of Vapour and Liquid. 



141 



t 



3 



20° 



40° 



60° 



80° 



100° 



Peak.... 

 Pobs.... 



A 



s 



0-00574 

 000605 

 000031 

 216-6 



0-02248 

 0-02288 

 0-00040 

 59-30 



0-07183 

 0-07225 

 0-00042 

 19-81 



0-1956 

 0-1958 

 00002 

 7-725 



0-4665 

 0-4666 



o-oooi 



3-422 



1 

 1 

 

 1-677 





t 



120 3 



140° 



160° 



180° 



200° 



220° 



Pcalc... 

 Pobs.... 

 A 



1-962 

 1-960 

 -0-002 

 0-8927 



3-571 

 3-569 

 -0002 

 0-5085 



6-106 

 6-118 

 0-012 

 0-3060 



9-907 

 9-922 

 0015 

 01924 



15-37 

 15-35 

 - 0-02 

 0-1253 



22-97 

 22-88 

 - 0-09 

 0-08371 







t 



240° 



260° 



280° 



300° 



320° 



332°-32 



Pcalc... 



33-23 

 0-05700 



46-73 

 0-03912 



64-15 

 0-02680 



86-27 

 0-01796 



113-9 

 0-01111 



1341 



0005892 





Comparison of the calculated and observed tensions shows 

 a very satisfactory accordance within the entire interval from 

 0° to 220°; accordingly it may well be assumed as probable 

 that the calculated values of the tensions for the higher tem- 

 peratures also, as well as the calculated critical temperature 

 332°*32, and the corresponding pressure of 134 atmospheres, 

 do not deviate too far from the truth. 



Now, as to the other constants which occur in the formulas, 

 for R, according to equation (8), if we put therein for d the 

 value 06221, which results from the values found by Reg- 

 nault for the specific gravities of hydrogen and oxygen, we 

 get 



R=47-05. 



From this it follows, further, according to (9), if for T c 

 and P c the values above found be employed, that 



7=0-002569. 



To determine a, from an observed volume of liquid water the 

 calculated value of w for the same temperature must be sub- 

 tracted. Now liquid water, when heated from 0°, exhibits the 

 peculiar phenomenon that at first it contracts, and only ex- 

 pands above 4°, and that even then, within a considerable 

 interval of temperature, its coefficient of expansion is much 

 more variable than those of other liquids. This phenomenon, 

 which is unquestionably connected with those molecular forces 



Phil Mag. S. 5. Vol. 13. No. 79. Feb. 1882. M 



