32S SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 5 1 



y the specific humidity or the quantity of vapor in a unit mass of 

 moist air expressed in fractional parts of this unit. 



/? the pressure to which this mixture is subjected expressed in 

 millimeters of mercury. 



/? the pressure of the standard atmosphere or 760™™. 



a the coefficient of expansion of air = 0.00367 = 1/273. 



/ the temperature of the mixture. 



Recalling that 1 cubic meter of dry air at o° C. and under a pressure 

 jf 76o mm weighs 1293 grams, and that the density of aqueous vapor 

 is 0.623 times that of dry air at the same temperature and pressure, 

 then we have the following equations: 



/ = 0.623 X 1293^x^-1.060^ ..(1) 

 R = 100 * (2) 



* = 0.623^ (3) 



p — e 



* - rh - °- fl23 /» - o.m, (4) 



Since the quantities x and y axe always among the hundredths there- 

 fore in many cases it will be advisable to multiply the value by 1000, 

 that is to say, we use the number of grams of vapor that are mixed 

 with a kilogram of dry air, or that are contained in a kilogram of 

 moist air respectively. 



If we indicate these values by x g and y g then we have 



*, = 623-^ (3a) 



and 



* ~ 623 /3^T377l " 100 ° lOOT^T, ' • • ' (4a) 



In the headings of the tables that are to follow, as also in the dia- 

 grams, I will, for the sake of clearness, omit the subscript index g 

 and will by x and y understand quantities 1000 times as large as 

 those given by the preceding definition. 



