for the elastic force of Steam. 



103 



For the vapour of hydrochloric ether, determining the con- 

 stants a and b in the formula p = (a + b t) 6 from the experimental 

 results at the temperatures 0° C. and 100° C, we find 



a = 2783579, 

 b= -01753492, 



which give the results in the third column of Table IV. ; and 

 M. Regnault's corresponding results, from his Table at page 

 446 ; vol. ii., are given in the second column. 



Table IV. 



Temperature Centi- 

 grade by air-thermo- 

 meter. 



Elastic force of vapour 

 of hydrochloric ether 



Calculation by Alex- 



by interpolation 

 formula. 



ander's formula. 



o 



millims. 



millims. 



-30 



110-24 



132-374 



-20 



18755 



207360 



-10 



30209 



314-829 







465-18 



465-180 



+ 10 



69111 



671-130 



20 



996-23 



948035 



30 



1398-99 



1314-236 



40 



1919-58 



1791-426 



50 



2579-40 



2405 017 



60 



340054 



3184-566 



70 



4405 03 



4164-196 



80 



561411 



5383-030 



90 



7047-51 



6885-700 



100 



8722-76 



8722-754 



The general accordance of the second and third columns war- 

 rants us in concluding that the elastic force of vapour of hydro- 

 chloric ether is expressed by the formula p = (a-\-bt) 6 . 



M. Regnault's experiments on the elastic force of the vapour 

 of essential oil of turpentine extend from 0° C. to 200° C, and 

 by calculating the constants a and b from the pressures at 0° C. 

 and 100° C, the formula does not well accord with the observa- 

 tions; and taking the observations at 50° C. and 150° C, to 

 determine the constants, the results of calculation and observa- 

 tion diverge greatly also ; but taking the pressures at the tem- 

 peratures 100° C. and 200° C. to determine a and b } the for- 

 mula shows a general accordance with the results of observation, 

 with, however, occasional differences of considerable magnitude. 

 These latter give 



a= 1-029373, 



b= -01224551, 

 with which the results in the third column of Table V. were 



