6 PROPERTIES OF STEAM AND OTIIKR VAPORS. 



Pressure of Steam at Latitude 45. English System. To reduce the 

 equations for the pressure of steam, so that they \\ ill givi the pressm 

 pounds on the square inch for degrees Fahrenheit, tin re are required the 

 Comparison of measures of length, and of weight, the comparison of the 

 scales of the thermometers, and the specific gravity of mercury. 



Professor Rogers * gives for the length of the metre, 39.3702 inches. 



Professor Miller f gives for the weight of one kilogram, 2.20462125 

 pounds. 



Regnault gives, for the weight of one litre of mercury, 13.5959 kilograms. 



The degree Fahrenheit is of the length of the degree Centigrade. 



Let k - '3-5959 X 2.204621 . 



39.3702* 



then the equations B and C have for the reduction to degrees Fahren- 

 heit, and pounds on the square inch, 



log p = flj + log k - ba\* + cpl n , 

 log p = a, + log k - 6,0,1" + c, 0,K 



The resulting equations, which were used in calculating Table I, arc : - 



B. For steam from 32 to 212 F., in pounds on the square inch, 



log p = a 2 6a 2 n -f cp t n . 



a, = 3.025008. 

 log b = 0.6117400. 

 logc = 8.13204 10. 

 log a, = 9.998181015 10. 

 log /? 2 = 0.0038134. 



n = / - 32. 



C. For steam from 212 to 428 F., in pounds on the square inch, 



log p = a,- V* n + 'A n - 



2 = 3-74397 - 

 log 6, = 0.4120021. 



lg c i = 7.74168 10. 



k>g2 = 9.998561831 - 10. 



log Pi = 0.0042454. 



n = / 212. 



* Proceedings of the Am. A cad. of Arts and Sciences, 1882-83, also Additional Observa- 

 tions, etc. 



t Phil. Transactions, cxlvi., 1856. 



