Ionization produced hi/ Heated Salts. 385 



the current remained practically constant at a value of 

 2*1 x 10" 10 ampere for over an hour. The dotted portion 

 o£ curve 2, fig. 6, shows a rise o£ current to a maximum 



Fiff. 6. 



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I 



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400 



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1 















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1 



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 1 

































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40 



30 



20 



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ZO 40 zo 40 60 so 

 Time- Minutes 



100 izo 



value after ten minutes' heating. This was not as definitely 

 indicated in some similar experiments. It is difficult to say 

 whether or not such a relation exists, since it is quite likely 

 that there is a considerable temperature lag in the glass. 

 To overcome this difficulty the furnace was heated about 

 fifty degrees higher than the temperature required, the tube 

 was then inserted and the currents in the heating apparatus 

 regulated to values which experience had shown would give 

 the desired constant temperature. The positive ionization 

 increased slowly with time from a value of lx 10~ 10 ampere 

 to a maximum value of 5*8 xlO -10 ampere after 80-100 

 minutes, followed by a slow decay period. It is of interest 

 to note the dissimilarity in the positive current-time relations 

 shown in curve 1, fig. 6, and curve 3, fig. 3. The tem- 

 perature and pressure conditions were nearly identical in 

 the two cases ; the testing vessels were entirely different. 

 The negative ionization effects are, however, in good accord 

 with those recorded in Table IV., tube B. Other experiments 

 similar to those described above were made at the same 

 temperature and with the same quantity of salt, but at a 

 pressure of 5-8 mm. The negative current fell initially 



