Intelligence and Miscellaneous Articles. 283 



phuric acid and polarized by a great electromotive force. It has 

 manifestlj escaped the notice of the authors that the phenomena 

 M^hich they have discovered were for the greater part already de- 

 scribed by me in the January number of Wiedemann's Annalen* 

 entitled " Ueber das Maximum der galvanischen Polarisation von 

 Platiuelectrodeu in Schwefelsaure." In this research I have com- 

 municated experiments on the influence of the concentration of the 

 acid, as well as the influence of the size of the electrodes, on the 

 value of the maximum polarization, and therefore also on the values 

 of the resistance of the voltameter which occur at the same time as 

 the values of the polarization. The subject of the researches of 

 Messrs. Gee and Holden is exclusively the observation of the 

 resistance ; and it entirely confirms the results which I pub- 

 lished. As regards also the cause of the interesting phenomena, 

 the authors confirm the conclusions which I have made known. 



I may therefore here restrict myself to a brief collation of those 

 passages iu my paper from which are seen the great variations in 

 the values both of the polarization and of the resistance of a volta- 

 meter, which change with the maguitude of the resistance of the 

 rheostat ; assuming that the voltameter contains sulphuric acid of 

 47"^ to 57° per cent., and between a small polished platinum anode 

 and a platinum kathode of any size and condition. 



The electromotive force of the polarizing current may amount to 

 10-12 volts. If, then, the current is closed with a great resistance 

 in the rheostat, innumerable small bubbles of gas arise from the 

 kathode as well as from the anode, the deflexion of the galvano- 

 meter is very constant; the resistance of the voltameter is greater 

 than that given by the law of resistance of sulphuric acid, and its 

 polarization somewhat less than if it had been filled with acid of 40 

 to 45 per cent. 



If, now, the resistance of the rheostat is diminished, the strength 

 of the current at first increases, the number of bubbles of gas 

 ascending from the electrodes increases, while their magnitude at 

 first remains small. The needle of the reflecting-galvanometer 

 of a sudden begins to oscUlate strongly, and all at once sinks 

 to a considerably smaller deflexion, making continually smaller 

 oscillations about this. While a uniform current of small gas- 

 bubbles continually ascends from the kathode, only larger gas- 

 bubbles now rise from the anode with a hissing noise and at longer 

 intervals, 1 to 3 bubbles in the second according to the strength of 

 the current. This intermittent escape of gas-bubbles from the 

 anode is the cause of the oscillations of the needle, which take place 

 even with a strongly damped galvanometer. In this condition the 

 polarization of the voltameter is 1 to 2 volts higher than in the 

 preceding case ,: its resistance, however, contrary to the law of 

 resistance of sulphuric acid, is smaller than when it was filled 

 with 40 to 45 per cent, sulphuric acid. 



We still more diminish the resistance of the interposed rheostat ; 

 the current first of all increases. But suddenly the needle flies 



* C. Fromme, Wiedemann's Annalen, xxxiii. pp. 80-216 (1888). 



