Section u. The Specific-Volume Data. 35 



II. THE SPECIFIC -VOLUME DATA. 



All of the measurements have been included in table 1 (page 36) with 

 the exception of two, which, though agreeing well with the others, were 

 known to be less reliable. 



The first and second columns are self-explanatory. 



The third column gives the concentration of the solution at 4, expressed 

 in milli-equivalents per liter. 



The fourth column gives the corrected temperature of the measurement. 



The fifth column gives the number of grams of solution which were 

 weighed into the dry bomb at the start. 



The sixth column gives the volume, expressed in cubic centimeters, 

 which, at the temperature (135) at which the bomb was calibrated, corre- 

 sponds to the observed conductance-ratio. This volume was obtained by 

 interpolation from a plot made as described in section 8. The actual vol- 

 ume occupied by the solution at the higher temperature is greater than this 

 by an amount equal to the expansion of the bomb upon heating from 135 

 to that temperature. The temperature-coefficient of volume expansion of 

 the steel shell of the bomb is assumed to be 0.000038 per degree. 



The seventh column gives the specific volume of the solution at the tem- 

 perature of observation. It is obtained by dividing the values of the pre- 

 ceding column, after correcting them for the expansion of the bomb as 

 just described, by the weight of solution given in the fifth column. 



The last column gives the ratio of the specific volume at the round tem- 

 peratures 218, 281, and 306, to that of the same solution at 4. Thus, 

 this ratio shows the volume occupied by that quantity of solution which at 

 4 has a volume of 1 c.cm. The values are obtained from those of the 

 preceding column by reducing them to these temperatures by means of the 

 temperature-coefficient obtained from our specific-volume values, and then 

 dividing the results by the specific volumes of the solutions at 4. These 

 specific volumes are as follows: 0.9958 for 0.1 normal, and 0.9996 for 0.01 

 normal sodium chloride ; and 0.9954 for 0.1 normal, and 0.9995 for 0.01 

 normal potassium chloride.* 



12. SUMMARY OF THE SPECIFIC -VOLUME VALUES. 



The final results are brought together in table 2 (page 36). The value 

 at 140 is that found by Hirnf for pure water reduced from the higher 

 pressure which he employed to the vapor-pressure. 



*These values were computed from the densities given by Kohlrausch and Hall- 

 wachs ( Wied. Ann., 50, 122, 1893) for NaCl at 18, and from that given by Kohl- 

 rausch (Leitvermogen der Elektrolyte, 76) for a normal KC1 solution at 18, under 

 the assumptions that the change in density is proportional to the concentration and 

 that the expansion is the same between 4 and 18 for these solutions as for water. 



fHirn, Ann. chim phys. (4), 10, 32 (1867). 



