Section 49. Errors and their Elimination. 121 



tion and either diluting to the mark in a graduated flask or adding a 

 known weight of water. 



The water used in the preparation of the stock solution had a specific 

 conductance of less than 1.1 X 10". That used for preparing the 

 more dilute solutions had in almost all cases a specific conductance of 

 0.75-0.95 X 10- 6 . 



49. SYSTEMATIC ERRORS AND THEIR ELIMINATION. 



The possible errors affecting the conductivity values and their elimina- 

 tion or correction have been fully discussed in section 10, Part II. It is 

 therefore necessary only to refer to a few modifications of the corrections 

 applied and to some new difficulties met with in the experiments. 



VOLATILIZATION OF SOLVENT. 



The correction for the quantity of solvent in the vapor-space in the 

 bomb was applied in the case of the non-volatile solutes as before, it being 

 calculated from the known volume of the vapor in the bomb and its 

 specific volume interpolated or extrapolated from the data of Zeuner* 

 which extend up to 200. The correction requires an increase of the con- 

 centration of 0.01 per cent at 100, 0.03 per cent at 156, and 0.02 per cent 

 at 218 in the case of our experiments. Although certainly less than the 

 other errors it was always applied at 156 but not at the other tempera- 

 tures. 



VOLATILIZATION OF SOLUTE. 



In the case of the acetic and hydrochloric acid solutions the correction 

 for the vapor-space should also take into account the possible volatility 

 of these solutes. In these cases the total correction for volatilized solvent 

 and solute was experimentally determined at 218 by varying the quantity 

 of solution placed in the bomb and measuring the conductances. From 

 the variations of these with the known variations of vapor-space the cor- 

 rection for the vapor-space existing in the ordinary measurements could be 

 readily calculated. Thus, for three different volumes of a 0.01017 nor- 

 mal acetic acid placed in the bomb, the vapor-spaces and conductances at 

 2 J 8 were as follows: 



Vapor-space (cubic centimeters) . . 1.5 11.1 25.4 



Specific conductance X 10 6 447.3 447.8 448.5 



It is evident that since 24 c.cm. of vapor-space cause an increase in the 

 conductance of 0.27 per cent, that produced by the 1.5 c.cm. usually pres- 

 ent would be about 0.02 per cent, which is the magnitude of the correction 



Landolt-Bornstein-Meyerhoffer, Tabellen, p. 127 (1905). 



