26 



Scientific Proceedings, Roijal Diihlin Society. 



In order to compare more clearly the experimental results obtained for the 

 salt solution, an approximate correction for slight variations in the length of time 

 of their exposure to the air has been made. Eighteen days was taken as the 

 standard time, since four out of the nine tubes were exposed for that time. 



Adeney and Becker's formula for calculating the rate of re-aeration was 

 employed, viz. ;^ 



w = (ioj - v^) \i-c " y, 



where vj = amount of gas dissolved, expressed in percentage of saturation. 

 ii\= initial concentration in percentage of saturation. 



/ = coefficient of escape of the gas from the liquid per unit area and volume. 

 V = volume of liquid. 

 a = area of surface. 

 / = time of exposure. 



Di'pth in ceii'imeti'es. 

 Fig. 3. — Concentration of Xitrogen at \'aiions de[)ths after 18 d.iA s' rxnosure for ditfL'tent salt solutions. 



By means of the above equation, if u' be known for any time t, its value can be 

 found for any other time t. The mean value of the concentration of the gases in 

 solution in the liqitid was taken to be v-. The acttial values at various depths 

 were afterwards calculated. ('ur\'es were plotted for the columns of solutions, 

 using observations made after eighteen days. 'J'hey are given in fig. 3. 



The values fortlie concentrations of nitrogen at a depth of 200 cms. were 

 taken, and these values were plotted against the concentration of salt. The 

 nraximum concentration of nitrogen was found to obtain in a solution with a 



