424 PROCEEDINGS OF THE AMERICAN ACADEMY. 



with boilino- water. The great bulk of nitrate may tlien be removed by 

 one crystallization. If to the mother liquor is added a solution of ar- 

 gentic nitrate, the argentic nitrite will precipitate at once as a thick 

 yellow paste. This is washed and re-crystallized from hot water, until 

 the color has changed to white. The pure nitrite was dissolved in a 

 nitrate solution to saturation, and this was employed, first, with a porous 

 cup (IG), and second, with a paper-wrapped anode (17). 



The results show that a saturated solution of nitrite really has the 

 effect of increasing the kathode deposit. 



Since the increase due to a paper-wrapped anode over the weight 

 found with a porous cup would have been from 0.04 to 0.08 per cent, the 

 nitrite caused an increase of about the same amount in each case. But 

 this increase happens only when the solution is saturated with nitrite ; 

 hence it is interesting chiefly as a limiting effect, and can hardly be im- 

 portant in solutions of nitrite as dilute as those formed spontaneously 

 around the anode. The formation of nitrite is evidently the result of 

 the breaking up of the IsOg" ion into the nitrite ion 1^0.~ and ox3'gen, 

 and the latter is probably taken up by the silver in forming one of the 

 oxidized compounds to be discussed later. 



It is not at all surprising that this side reaction should take place to a 

 small extent. The current is normally cariied fi'om the anode to the 

 solution by the formation of the silver ion from the metal ; but a slight 

 tardiness in this reaction (which might be named " physico-chemical in- 

 ertia") would result in assistance from the anions in the neighborhood. 

 They would seek to adjust the potential by discharging their negative 

 electricity on the anode. Of course the most plentiful anion in the vicin- 

 ity is the nitrate ion ; its deionization would make possible the form- 

 ation of the nitrite ion and oxygen, which might at once oxidize the 

 silver plentifully present.* The reaction might be written thus: — 



NO3 -H 3Ag = Ag + -f NO2- -f Agp. 



Thus the electrolysis of a strong solution of argentic nitrate might be 

 predicted to result, in the neutralization of a previously acid solution — 

 a prediction which agrees with the fact discovered by Rodger and 

 "Watson t with thirty per cent solutions of argentic nitrate. It is pos- 

 sible that a higher oxide also would be found if the anode were small. 



* The probable presence of silver in supersaturated solution around the anode 

 will be shown later. 



1 Rodger and Watson, Phil. Trans., 186 A, G31 (1895). 



