82 F. E. Beach — Use of Otipric Nitrate in the Voltameter, 



rate piece of copper without a current. The purely chemical 

 corrosion of the cathode is more than that of the anode. The 

 addition of any considerable amount of sulphuric acid had the 

 effect of diminishing the weight of copper deposited. 



Hammerl* as the result of a detailed investigation comes to 

 the following conclusions : 



I. No change in the quantity of the deposit was observed 

 when a blank platinum surface was substituted for one which 

 had been covered with a deposit of copper. 



II. The change of concentration of the solution caused by 

 the passage of the current and the polarization dependent on 

 it cannot be satisfactorily prevented by agitation. In boiling 

 to agitate the fluid the deposit oxidizes almost completely to 

 CuO, and partially indeed between 40° and 60° C. 



III. The highest allowable current strength is 7 amperes 

 per square decimeter. The distance between the plates should 

 not be less than l*5 cm . 



Grayf finds that the highest current-density desirable is one 



ampere to 50 square centimeters ( = 0*02 — ^- ). He obtains 



Cu 



the ratio — — = 2940 and for the electro-chemical equivalent 

 2Ag 



of copper 0*0003287 — - — '—r— when silver is taken as 

 L x amp. sec. 



0-001118. He remarks " This would indicate a value not dif- 

 fering much from 0-0003290." He does not find as did Gore, 

 that loss by chemical action is less when the current is flowing 

 than when it is not. Copper was dissolved in the sulphate at 



the rate of 0*02 — ~,— Addition of sulphuric acid seemed 

 cm 2 , hr. 



to retard the loss when the density of the solution was between 



1-1 and 115. 



Gray:); using a density of the sulphate solution of 115 to 



118 with one per cent free sulphuric acid found that the 



equivalent depended on temperature and current-density in a 



manner which is exhibited by the following table. The factor 



10 ~ 7 has been omitted. 



rea of cathode iu 





Temperature. 







. cm. per ampere. 



2°C. 



12° C. 



23° C. 



28° C. 



35° C. 



50 



3288 



3287 



3286 



3286 



3282 



100 



3288 



3284 



3283 



3281 



3274 



150 



3287 



3281 



3280 



3278 



3267 



200 



3285 



3279 



3277 



3274 



3259 



250 



3283 



3278 



3275 



3268 



3252 



300 



3282 



3278 



3272 



3262 



3245 



* Wien. Ber., (2), lxxxviii, pp. 273-294. + Phil. Mag., xxii, p. 289, 1886. 

 X Phil. Mag., xxv, p. 179, 1888. 



