Prof. R. Bunsen's Special- Analytical Researches. 423 



1*938) is deduced for T. Formation of ozone and hydrogen 

 peroxide during electrolysis, as also uncertainty in reading- off 

 the position of the needle, were obviated by amalgamation and 

 subsequent heating of the platinum plates of the decomposition- 

 cell, which contained only a few grammes of water, and, further, 

 by beginning to collect the mixed gases only after decomposition 

 had proceeded for ten minutes, by which time the current had 

 become perfectly regular. The gases were collected, at a con- 

 stant pressure, in a measuring-flask over water previously satu- 

 rated with the same gases. After observation of the volume of 

 gas, the pressure, and the temperature, the measuring-flask was 

 carefully removed from the water and weighed with the film of 

 water which adhered to it, again filled with water to the point 

 read off in measuring the gases, and again weighed. From these 

 data the weight of water decomposed in the observed time t was 

 calculated. The deviation-angle of the needle altered very regu- 

 larly — in the first experiment only 7', in the second 9'. From 

 the whole of these estimations the following equation was de- 

 duced, and was used in calculating the intensity of the current, 

 in absolute measure, throughout the series of experiments, 



J = 62-23. 



cos (^-1° 58') 



The chromic-acid battery without clay cells is the least-con- 

 stant of the ordinary constant batteries. The curves in fig. 1 

 represent the current-diminution, A, of the ordinary carbon-zinc 

 battery, and, B, of the chromic-acid battery without clay cells, 

 in minutes and hours according to absolute measurement. The 

 apparent breaks in curve B indicate the times at which the zinc 

 plates were amalgamated. The current becomes constant much 

 sooner with the carbon-zinc or with Grove's than with the chro- 

 mic-acid battery, because the depolarization is much more com- 

 plete in the first than in the latter instance : this is shown by 

 the fact that, on shaking the chromic liquid, the current which 

 had become constant is considerably increased. If that portion 

 of the liquid which is in contact with the zinc plate be alone set 

 in motion, the increase of the current does not occur; polariza- 

 tion takes place therefore only on the coal, not on the zinc plate. 



The electromotive force of the chromic-acid battery without 

 clay cells considerably surpasses that of any of the ordinarily 

 used apparatuses. The amount of this electromotive force may 

 be estimated within tolerably narrow limits without exact mea- 

 surement : it must be greater than that of Grove's battery, con- 

 sequently greater than 18*5 ; for the current of a chromic battery 

 is able to overcome that of a Grove's battery, but not that of two 

 DanielPs cells : the electromotive force must therefore lie between 



