INORGANIC RESPONSE 141 



be produced in the internal resistance of the cell. The 

 effect of this on the deflection is eliminated by inter- 

 posing a very high external resistance (from one to five 

 megohms) in comparison with which the internal re- 

 sistance of the cell is negligible. The fact that the 

 introduction of the reagent did not produce any varia- 

 tion in the total resistance of the circuit was demonstrated 



Before f After 



FIG. 89. STIMULATING ACTION OF Na 2 CO s ON TIN 



by taking two deflections, due to a definite fraction of 

 a volt, before and after the introduction of the re- 

 agent. These deflections were found equal. 



I first give a record of the stimulating action of 

 sodium carbonate on tin, which will become evident by 

 a comparison of the responses before and after the 

 introduction of Na 2 C0 3 (fig. 89). The next record 



