joj Conductivity of Aqueous Solutions. Part X. 



measured. In most cases this was repeated till only a very slight increase 

 of conductance was observed.* 



The bomb was then put into the xylene bath heated by steam. When 

 the temperature of the bath had reached its former value, readings were 

 taken every five minutes, and as soon as no appreciable change in the 

 conductivity occurred, the conductivity was measured with three different 

 resistances in the rheostat. The bomb was then taken out of the bath, 

 shaken violently about 100 times, replaced, and readings -taken after heat- 

 ing for 40 to 60 minutes. 



Since at the end of these operations the specific conductance had 

 increased by about 1 X 10~ 8 , the change was at first ascribed to incomplete 

 saturation. If this were true, one would expect of course that upon 

 repeated shakings and heatings these increases would become less and less. 

 To test this view an experiment was made with silver chloride in which 

 the observed conductances measured at 99.7 at the start, and after suc- 

 cessive shakings and the stated periods of heating between each reading 

 were as follows : 



Period of heating (min.) 62 125 56 55 



Specific conductance X 10 6 59.72 60.47 62.73 64.25 65.77 



Increase per hour 0.72 1.08 1.62 1.68 



Considering in connection with these results the fact that even at room 

 temperature the saturation occurs almost instantaneously, it seems very 

 probable that these increases are not due, or are only in small part due, 

 to incomplete saturation ; for if they were due to this, one would expect 

 that the increase per hour would diminish instead of increasing. It is 

 more probable that the effect is mainly due to a slight decomposition of 

 the salt perhaps a reduction by impurities in the water. f It might also 



*These data at the room temperature are not given in the table below, as they 

 were not measured at any one temperature, their purpose being mainly to serve as 

 an indication of accidental contamination in any experiment. As a result of all the 

 observations it was found that the increases after shaking were small in comparison 

 with those taking place immediately after pouring in the water, showing that satura- 

 tion is attained very rapidly. This is illustrated by the following data. The conductance 

 immediately after closing the bomb at room temperature (22.7) was 2.754; and 

 after shaking successively the number of times shown by the figures in parentheses 

 it was: (2) 2.922; (2) 2.966; (2) 2.982; (2) 2.985; (4) 3.004; (4) 3.002; (10) 

 3.011; (10) 3.015; (100) 3.028; (100) 3.028- These numbers show, if we assume 

 3.03 as the final value corresponding to that temperature and 1.00 to be the conduct- 

 ance of the water, that 86 per cent of the silver chloride goes into solution during 

 the short period of pouring in the water and closing the bomb and 98 per cent after 

 shaking the bomb 8 times. Whether the later increase of 2 per cent is a consequence 

 of further solution of the salt or whether it is due to a rise of temperature brought 

 about by the process of shaking is uncertain. 



fit was found in general on bringing the contents of the bomb back to room tem- 

 perature that the conductance had increased by an amount which was greater 

 the longer the duration of the previous heating. In one case the conductance of 

 the saturated solution at 29.1 before heating was 3.84 X10~ 6 reciprocal ohms, while 

 upon returning to that temperature after heating for 60 minutes it had become 

 4.16 X 10-. 



