On the Heating Power of the Galvanic Current. 209 



phuric acid, there is always a notable excess of hydrogen ; in one 

 case the oxygen was only one-fifteenth of the whole volume of 

 gas evolved. With solution of potash a similar result takes 

 place. 



2nd. When the quantity of acid is increased to the point at 

 which the electrolytic power of the solution is the best, the ex- 

 cess of hydrogen is less ; and probably if the exact point of the 

 solution were attained, there would be no excess. 



3rd. When the solution is much stronger than that which 

 makes the best electrolyte, there is a notable excess of oxygen. 



4th. When the electrodes exceed a certain size, water conducts 

 without any apparent signs of decomposition. 



if)n making a search for any previous experiments on this sub- 

 ject, I find that Faraday (Phil. Trans. 1834, p. 91) has observed 

 that when a strong solution of sulphuric acid, formed by mixing 

 two measures of oil of vitriol with one of water, was subjected to 

 ordinary electrolysis, a remarkable disappearance of oxygen took 

 place. The strength of the acid he then employed would be 

 very nearly that employed by me in experiment 7 ; but in my 

 experiment, when the solution is subjected to decomposition by 

 the spark from the secondary coil, exactly the converse eficct 

 takes place, and there is a notable disappearance of hydrogen. 



Faraday attributes the disappearance of the oxygen to the 

 formation of peroxide of hydrogen ; but in those of my experi- 

 ments where oxygen disappeared, this could hardly be the case, 

 as the gases are eliminated at a point of ignition at which this 

 compound would be decomposed, and in many of my experi- 

 ments the liquid was kept very nearly at the boiling-point. 



I abstain at present from expressing any opinion as to the 

 cause of these singular anomalies, and hope to make a further 

 communication on the subject when I can resume and complete 

 some experiments which I have in view, but which it will be 

 some time before I can undertake. 



XXXIV. On the Dependence of the Heating Power of the GaU 

 vanic Current on the nature of the surrounding Gas. By 

 R. Clausius. 



WE take the following from a paper published by M. Clausius 

 in the 12th Number of PoggendorfF^s Annalen for 1852. 

 It shows the attention which the remarkable experiment of Grove 

 (Phil. Mag. vol. xxvii. p. 445) has attracted in Germany, and also 

 the different opinions entertained as to the cause of the observed 

 phsenomena. In the circuit of a voltaic battery Grove intro- 

 duced two perfectly similar pieces of platinum wire, coiled into 



