Section 66. Summary of Equivalent Conductances. 



171 



values, since these were not affected by polarization. In all other cases 

 the mean of the initial values will be adopted. 



Table 55 contains the results for ammonium chloride, which are derived 

 from measurements with solutions of the salt containing about one- 

 tenth as many equivalents of ammonium hydroxide (see table 53) by 

 correcting the observed conductance for the conductance of the ionized 

 portion of the base. In the case of the first two measurements (made on 

 May 17), however, no free ammonia was added. 



Table 55. Equivalent conductance of ammonium chloride at 



round temperatures. 



The results of the separate experiments with ammonium chloride given 

 in table 55 are in almost complete agreement. The two measurements of 

 May 17 at 18, made with the salt alone without the addition of ammonia, 

 show that no considerable contamination resulted in the other cases from 

 the presence of the base. A comparison of the initial and final values 

 shows that no change in conductance was produced by the heating in the 

 12.5 milli-normal solution, but that there resulted from it an increase of 

 0.7 per cent at 100 and of 1.0 per cent at 18. It has therefore seemed best 

 to decrease the value at 156 at 2 milli-normal by 0.5 per cent in order to 

 eliminate this effect as far as possible. This will be done in table 58 where 

 the best values are brought together. 



The initial and final values at 18 obtained with ammonium hydroxide 

 (table 56) show that the heating had scarcely any effect on the 100 milli- 

 normal solution, but that it caused a decrease of 0.7 per cent in the 33, 

 and of 1 per cent in the 10-milli-normal solution. That this decrease, 

 occurring in spite of the fact that almost any contaminating substance 

 either by its own conductance or through salt-formation would produce an 

 opposite effect, is due to destruction of the ammonia by oxidation, has 

 been shown in connection with experiments made at 218 by Mr. R. B. 

 Sosman in this laboratory, which will be later described. The effect in 

 our experiments was fortunately not so great as to produce an important 

 error, and it has seemed best not to attempt to correct for it, since contami- 

 nation tends to compensate it. 



