INTRODUCTION. 



All of the foregoing equations make the pressure a function of the tem- 

 perature on the scale of the air-thermometer. It will be imimH that the 

 difference between that scale and the absolute scale may be neglected. 



Pressure of Other Vapors. Regnault determined aUo the pressure 

 of a large number of saturated vapors at various temperatures, and 

 deduced equations for each. The equations and the constants as deter- 

 1 by him fur the commoner vapors are ^i\ m in the following table: 



Alcohol 



Chloroform . 

 Carbon bisulphide . 

 Carbon tct rachloride 



i -.- ; 



a -fc^+ 

 a + ba* - 

 a -6a" - 

 a-6a" 

 a -fca - 



cjT 

 c0 



$" 



OMBM 



\ 

 o 



I '.-.:!-! 



i 

 p 



.- . 

 . .. . 

 o 



o 



I ,74S' 



Zeuru-r * >t;ites that there is a slight error in Regnault's calculation 

 of the constants for aceton, and gives instead 



log p -"/i - 60* 4. f v ; 



o -5308M19; 



log 6a* - +O.A312766 -0.00261481; 

 log <* - - .9645222 - 0215592 1. 



Dififerential Coefficient ' - . As will be seen later, the differential 



at 



coefficient - - is used in calculating the volume and density of saturated 

 at 



vapors. 



From the general equation of the form, 



log p - a + 6a + eft", 

 differentiation gives 



Js-S5* 1 ga -"" + ^ rl0g ' 9 

 in which M is the modulus of the common system of logarith 



