l+« 273+T 

 * 273 + 6 



Temperature and the Tension of Vapours, 11 



The great exactness with which the tension of aqueous vapour 

 has been experimentally determined throughout a wide range of 

 temperature allows of our submitting the applicability of the 

 formula 



~P=p.lO 



to a rigorous test. Its employment, however, is not limited to 

 this case ; for the theoretical considerations which led to the use 

 of this formula for the determination of the tension of aqueous 

 vapour apply with equal force to the vapours of other liquids. I 

 have only investigated the comportment of saturated vapours of 

 alcohol, ether, sulphurous acid, and ammonia in this respect. 



The Tables given by Regnault in ComptesRendus, vol.1, p. 1663, 

 furnished me with the data for the determination of the values 

 of a. 



The tension of saturated alcohol-vapour is given in these Tables 

 from —20° to +155°, increasing in each case by 5°. Using 

 these numbers of Regnault's, and taking the temperature (r) at 

 100° C, the mean values of u were calculated from the formula 



a= 0-0843 + 0-00019 t + 0*00000032 r% 

 or, on counting the temperature from 0°, from the formula 



a =0-0685 + 0-000126 T + 0-00000032 T 2 . 

 At 100°, P is assumed = 1694-92 millims.; for other tensions, 

 therefore, i+« 1os 273+t 



pmm =1694-92x10 a 373 . 



The results of these calculations are embodied in the follow- 

 ing Table, the column R. of which contains the tensions that 

 Regnault calculated from his experiments. 



nno 



«. 



pp. 



?• 



E. 



dd. 



- 20 



006611 



11-6 



12-3 



12-9- 



13-6 



14-2 



14-8 



15-5 



161 



16-8 



17-4 



180 



18-7 



19-3 



200 



20-6 



21-2 



21-9 



3-24 



3-34 



- 0-10 



- 10 



006727 



6-63 



6-58 



+ 005 







006850 



1302 



1283 



+ 019 



+ 10 



0-06979 



24-60 



24-30 



+ 0-30 



20 



007115 



4475 



44-18 



+ 0-27 



30 



0-07257 



78-61 



78-49 



+ 012 



40 



007405 



13312 



133-64 



- 0-52 



50 



0-07560 



218-82 



219-88 



- 106 



60 



007721 



348-38 



35026 



- 1-88 



70 



0-07889 



538-73 



541-21 



- 2-48 



80 



0-08063 



809-66 



812-76 



- 3-10 



90 



0-08243 



118713 



1188-43 



- 1-30 



100 



008430 



1694-92 



1694-92 



000 



110 



008623 



2366-95 



2361-63 



+ 5-32 



120 



0-08823 



322760 



3219-68 



+ 7-92 



130 



0-09029 



4314-10 



4301-04 



+ 1306 



140 



09241 



565110 



5634-00 



+ 1710 



150 



0-09460 



7265-40 



7258-73 



+ 667 



155 



0-09572 





8168-60 



8185-02 



-16-42 



