104 On Mr. Alexander's formula for the elastic force of Steam* 



calculated ; and M. Regnault's corresponding results, from his 

 Table, page 501, vol. ii., are given in the second column. 



Table V. 



Temperature Centi- 

 grade by mercurial 

 thermometer. 



Elastic force of vapour 

 of oil of turpentine 



Calculation by Alex- 



by interpolation 

 formula. 



ander's formula. 



o 



millims. 



millims. 







207 



1190 



10 



2-94 



2-335 



20 



4-45 



4-281 



30 



6-87 



7-425 



40 



10-80 



12-294 



50 



16-98 



19-574 



60 



26-46 



30140 



70 



40-64 



45-084 



80 



61-30 



65-750 



90 



90-61 



93-772 



100 



13111 



131110 



110 



185-62 



180-092 



120 



257-21 



243-458 



130 



348-98 



324-406 



140 



46402 



426-640 



150 



605-20 



554-419 



160 



775 09 



712-615 



170 



975-42 



906-760 



180 



120792 



1143114 



190 



1473-24 



1428-722 



200 



1771-47 



1771470 - 



Though the differences in the above Table are in some cases 

 large, yet I think the general accordance of the second and third 

 columns is sufficient to warrant our concluding that the elastic 

 force of vapour of oil of turpentine is expressed by the formula 

 p = (a + bt) G . This last example shows that it is not safe to take 

 any two observed pressures and temperatures for the purpose 

 of determining a and b from the Tables, but the values obtained 

 should be applied to the other temperatures and pressures before 

 we can rely upon them. 



As the computations are tedious, I shall not proceed further at 

 present with the numerous vapours examined by M. Regnault, 

 having satisfied myself that the elastic force of the vapours 

 generally is expressed by Mr. Alexander's formula. 



For the six liquids of which the elastic forces of the vapours 

 have now been shown to be expressed by the formula p = (a-\-bl) 6 , 

 we have the following formulas for p expressed in inches of mer- 

 cury and t in Fahrenheit's degrees. 



For steam or vapour of water (Mr. Alexander's formula in 

 decimals), p= (-5840708 + '00555555 *) 6 . 



For vapour of alcohol, 



p = (-691898 -f -0062885 tf. 



