HYGROMETRICAL TABLES. XXXVU 



The argument of the table is given for every two-tenths of a degree 

 Fahrenheit from — 6oro to 32°o Fahrenheit. The tabular values are given 

 in millimetres and inches to three and four decimals respectively. 



TABLE 38. 



TABLES 38, 39. 



Weight of aqueous vapor in a cubic foot of saturated air — 

 English measures. 



TABLE 39. Weight of ag7ieous vapor in a cubic metre of saturated air — 

 Metric m.easures. 



The weight of aqueous vapor in a aibic metre of saturated air is given 

 by the expression 



I -\- at ' 760' 



a is the weight of a cubic metre of dry air (free from carbonic acid) 

 at temperature o° C. , and pressure of 760 millimetres of standard 

 mercur>' at 45° latitude and sea-level: a = 1.29278 kg. (Bureau 

 International des Poids et Mesures : Travaux et Memoires, t. I, p. 



A 54.) 

 8 is the density of aqueous vapor : 8 =0.6221 

 F is the pressure of aqueous vapor in saturated air whose temperature 



is / ; Broch's values are adopted, expressed in millimetres. 

 a is the coefficient of expansion of air for 1° C. : a = 0.003667 

 / is the temperature in Centigrade degrees. 

 Whence we have 



W (grammes) = i .0582 1 x _^-^^^^ • 



Table 39 is computed from this formula and gives the weight of vapor 

 in grammes in a cubic metre of saturated air for dew^-points from — 29° to 

 40° C, the intervals from 6^ to 40° C. being o°i C. The tabular values are 

 given to three decimals. 



The weight W of aqueous vapor in a cubic foot of saturated air is 

 obtained by converting the foregoing constants into English measures. 



The weight of a cubic foot of dry air at temperature 32° F. and at a 

 pressure of 760 mm. or 29.921 inches is 



<( ■ \ 1 292.78x15.43235 _ ^^^ ^^ 



a' (grams) = -. -— r — r:^ — 5o4-94- 



^ (3.280833)3 



We have therefore, 



a' 8 F' 

 W (grains) = x — - — j-,-, -— ^ 



^^ ^ 29.921 I +a'(/' — 32 ) 



_ F 



-ii.7459j^o;oo2037(^'-32°) 



The temperature t' is expressed in degrees Fahrenheit ; the vapor 

 pressure F\ expressed in inches, is obtained from Table 35. 



