CALCULATION OF RESULTS. 85 



for the Elster meter (see p. 47), the cologarithm of the correction 

 corresponding to the temperature of the meter T m , i. e.,(i +.00367 

 T m ) , and the logarithm corresponding to the corrected pressure. The 

 pressure of the air in the meter during the process of taking the resid- 

 ual sample is affected by three factors first, the atmospheric pressure ; 

 second, the tension of aqueous vapor at the temperature of the meter, 

 and third, the tension of the air on the meter as measured by the water 

 manometer. By referring to the data given for the water manometer 

 on the blank (p. 64), it is found that in this instance the manometer 

 when reduced to millimeters of mercury indicates 12.28 mm. The 

 temperature of the meter was 20.44, afl d the tension of aqueous vapor 

 at this temperature indicated in the calculations by e equals 17.84 mm. 

 The sum of these two pressures equals 30.12 mm., which must be de- 

 ducted from the barometric pressure to give the corrected pressure on 

 the air in the meter, namely, 725.66 mm. The logarithmic correction 

 for this pressure, i. e., p-t-j6o, is .97992. The true volume of air 

 then drawn through the meter is 8.672 liters. This does not, however, 

 represent the total volume of air withdrawn from the chamber in the 

 sample, since there were 0.0554 gram of water and 0.0441 gram of car- 

 bon dioxide absorbed in the U tubes before the air entered the meter. 

 By converting these weights to volume by means of the standard log- 

 arithmic factors, .09462 and .70680, we find there was withdrawn from 

 the air system in the sample 0.069 liter of water vapor and 0.022 liter 

 of carbon dioxide, thus showing that the total volume of air withdrawn 

 in the process of taking a sample, v n) was 8.672 -f 0.069 + 0.022 = 8.763 

 liters. The logarithm of this amount is .94265 and the cologarithm 

 5735- This is more clearly expressed algebraically as follows : 



CALCULATION OF TRUE VOLUME OP SAMPLE FOR DETERMINATION OF CARBON 



DIOXIDE AND WATER. 



v = volume of air sample containing carbon dioxide and water 



vapor at o and 760 mm. 



v = apparent volume of sample (i. e., meter reading). 

 f = factor for correcting meter readings. 

 w = weight of water in sample. 

 w l = weight of carbon dioxide in sample. 



1.2434^ = theoretical volume of water vapor at o and 760 mm. 

 0.5091 w 1 volume of carbon dioxide at o and 760 mm. 

 T m temperature of water (air) in meter. 



e = tension of aqueous vapor at T m (millimeters of mercury). 

 m manometer reading, expressed in millimeters of mercury. 



