10 SATURATED STEAM, AND OTHER VAPORS. 



Other Equations for the Pressure of Steam. Kunkine, in his Steam 

 Engine and other Prime Movers, gives the following equation : 



For pounds on the square inch, corresponding to degrees Fahrenheit, 



A = 6.1007. 

 log B = 3.436 1 

 log C = 5.59873. 



T = t + 461.2F. 



This equation has been largely used for calculating tables on the English 

 system. The following table will give a comparison between the results from 

 this formula and those from Formulae B and C. 



TEMPERATURE. 1 U K8SUBE. 



Refnaalt at 45* latitude. Raoklne. 



32 0.0890 0.083 



77 0.4555 0.452 



122 1.7789 1.78 



167 ..:.79 5.58 



212 11.99 14.70 



257 33.711 33.71 



302 69.27 69.21 



347 129.79 129.8 



392 225.56 225.9 



428 336.26 336.3 



Differential Co-efficient -. As will be seen later, the different ial 

 at 



co-efficient -,- is used in calculating the volume and density of saturated 



vapors. 



From the general equation of the form, 



log p = a + ba* + c/3", 

 differentiation gives 



d 



m which 3f is the modulus of the common system of logarithms. 

 The equation may be written, 



The calculation of the values of the constants gives the following results 

 for latitude 45 : 



