jo Conductivity of Aqueous Solutions. Part II. 



temperature in question, but under a pressure of 14.8 atmospheres, may be 

 obtained. At 135, the mean temperature of the calibration experiments, 

 the vapor pressure is 3.1 atmospheres. Hirn's result should then be reduced 

 to this pressure. The coefficient of compressibility of water has been 

 investigated by Pagliani and Vicentini* up to 100. By plotting their values 

 and extrapolating, 0.000018 is found for the coefficient at 135, or for the 

 fractional decrease in volume per atmosphere pressure. Hirn's value 

 should then be increased by 0.000018 X (11.8 3.1) X 100 = 0.056 per 

 cent. Multiplying the value so obtained by the weight of solution employed 

 and by the specific gravity of the cold solution referred to water at the 

 same temperature, the volume corresponding to the observed conductance- 

 ratio is obtained. 



9. PREPARATION OF THE SUBSTANCES AND SOLUTIONS. 



The sodium chloride used was purified by precipitation with hydro- 

 chloric acid gas. It was then washed with hydrochloric acid, dried, and 

 finally ignited until decrepitation ceased. 



The potassium chloride was precipitated twice with hydrochloric acid 

 gas, crystallized from hot water, dried, and finally ignited. 



Solutions were made up, by weighing out the salts, so as to be almost 

 exactly 0.1 and 0.01 normal at 4. The solutions of smaller concentra- 

 tion were made by diluting the 0.01 normal one with the help of two grad- 

 uated flasks. 



The equivalent weights used are as follows : K = 39.14, Na = 23.05, 

 Q = 35.4G. All weighings were reduced to a vacuum. 



The water used throughout this investigation was prepared by redis- 

 tilling ordinary distilled water to which alkaline permanganate solution 

 was added from a steam- jacketed copper still with a tin condenser. The 

 first quarter of the distillate was rejected, and the following portions were 

 condensed hot (between 60 and 90). The water had a specific conduc- 

 tance of (0.7 to 1.0) X 10" 6 reciprocal ohms. 



10. DISCUSSION OF THE SYSTEMATIC ERRORS AND THEIR CORRECTION. 

 ERRORS AFFECTING THE SPECIFIC-VOLUME VALUES. 



(1) In calculating the specific-volume, the volume of the bomb was 

 directly determined at about 135, as described in section 8, and the 

 expansion of the metal from this point to the temperatures of the experi- 

 ments was corrected for Andrews,f working with "soft" cast steel, which 

 corresponds to the material from which the bomb was constructed, found 



*Landolt-B6rnstein-Meyerhoffer, Tabellen, 60 (1905). 

 fProc. Roy. Soc, 43, 299 (1887). 



