RICHARDS AND HEIMROD. — THE IMPROVED VOLTAMETER. 425 



But Kahle * found that in weaker solutions acid is produced instead 

 of being removed, and we have verified his results. Clearly this must be 

 due to yet another irregularity. Wlien the solution is dilute and neutral, 

 oxygen and hydroxyl ions are both present in appreciable amount, ac- 

 cording to modern electrochemical interpretation. Their greater ease of 

 deionizatian would compensate for their relatively small concentration, 

 and traces of negative electricity might be cai-ried out of the solution 

 through their agency with the formation again of argentic oxide, or even 

 oxveren gas. The reaction would, however, leave an excess of ionized 

 hydrogen (acid) in solution, a state of affairs not paralleled in the case of 

 the nitrite. This would explain the phenomena in question. 



But would not the argentic oxide at once dissolve in the simultaneously 

 formed acid, and thus form argentic nitrate again? Or, in other words, 

 does argentic oxide form with silver an oxide-complex of any degree of 

 stability? Hellwigtin a recent paper has shown that the weak silver 

 ion in the presence of the strong NOs" ion tends to strengthen itself by 

 taking up a molecule of some other undissociated substance, as AgCl, 

 Agl, AgBr, or AgCN. He has proved also that the solution actually 

 contains ions like Agol"*", since on electrolysis the iodine accumulates at 

 the kathode, and disappears from the anode. 



lu order to find if argentic oxide could in a similar way associate itself 

 with the silver ion, we boiled very pure argentic oxide with a concen- 

 trated solution of argentic nitrate, and filtered the solution hot. Upon 

 "being diluted with cold water this solution yielded a white precipitate, 

 which tui-ned gray upon standing. The precipitate was soluble in dilute 

 nitric acid, hence it could not have been an argentic halide ; besides, 

 every precaution had been taken to exclude the halogens. The com- 

 pound precipitated on dilution must, therefore, be silver hydroxide or a 

 basic salt; and a basic complex must have existed in solution. 



It is by no means inconceivable that this complex, although finally de- 

 composed by acid, should not yield at once to its action. In the meantime 

 the acid, diffusing at a far more rapid rate than the heavy complex, would 

 have partly left the immediate neighborhood of the anode, and hence the 

 heavy solution around the latter would fall with its basic load to the 

 bottom of the kathode vessel. There the complex ion (possibly AgjO^) 

 would be capable of transferring electricity as well as any other ion, and 

 upon deionization would deposit over three times the weight of material 



* Kalile, Wicd. Ann., 67, 1 (1899). 



t Zeilsclir. aiiorg. Cheui., 25, 157 (1900). 



