94 Conductivity of Aqueous Solutions. Part IV. 



In regard to these experiments a few remarks of a special character may 

 be added. In the case of silver nitrate it was observed, when the bomb 

 was rinsed with absolute alcohol and ether and the adhering portion of 

 the latter solvent allowed to evaporate, that there was, even at 218, a 

 rapid progressive decrease in the conductance of the solution and that 

 this was due to an extensive reduction of the salt. In fact, in two experi- 

 ments, one at 218 and one at 306, it was found upon cooling and open- 

 ing the bomb that it was entirely coated with a crystalline deposit of metal- 

 lic silver, and that the solution contained no silver and no acid whatever, 

 giving no precipitate with hydrochloric acid and no color change with lit- 

 mus. Since the minute quantity of organic matter present could not pos- 

 sibly cause this reduction, it is evident that the decomposition when once 

 started goes on spontaneously, the reaction being apparently catalyzed by 

 the metallic silver. This remarkable phenomenon was not observed when 

 the bomb was rinsed with pure water and quickly dried at 100, or when 

 rinsed with the solution, except in the last experiments at 281 and 306 

 made with the strongest (100 milli-normal) solution; in these cases a 

 slow decrease in conductance occurred, and the conductivity-values given 

 are therefore less reliable than usual ; yet since they have been corrected 

 upon the basis of measurements of the rate of change they are probably 

 not in error by more than 1 per cent. 



In the case of the 100 milli-normal barium nitrate solution at 306 a 

 steady decrease in conductance was also observed, but, since upon return- 

 ing to 18 the conductance was found to be the same as before the heating, 

 the observed change was doubtless due to the gradual separation of the 

 salt itself or of a basic derivative of it from the solution. We did not 

 therefore obtain reliable measurements at this concentration at 306, but in 

 place of them we investigated at that temperature a somewhat more dilute 

 solution (80 milli-normal) in which the change, though noticeable, was 

 so slow as to introduce no important error. 



In the experiments with magnesium sulphate a similar decrease in 

 conductance was observed with the 350 milli-normal solution at 218 and 

 even with an 80 milli-normal solution at 306. In the former case a white 

 crystalline deposit was found in the bomb upon cooling and opening it 

 without shaking, and the solution was found by titration to contain con- 

 siderable acid. On account of the large hydrolysis and the separation of 

 a solid phase, even in fairly dilute solution, no attempt was made to carry 

 the measurements above 218. 



