MR. DANIELL ON VOLTAIC COMBINATIONS. 
117 ' 
battery by breaking the metallic contact is now perfectly intelligible ; and we can no 
longer be at a loss to understand all the phenomena of Ritter’s secondary piles, the 
effects ascribed to polarity by M. Becquerel, and the experiments of Marianini and 
A. De la Rive upon this interesting subject. 
I have remarked in the dissected battery, that when any oxide of copper was pre- 
sent in the solution, it was thrown down in preference to the oxide of zinc ; and that 
plates which had become covered with the former metal were, in some degree, pro- 
tected from depositions of the latter. Upon adding, however, sulphate of copper in 
any considerable quantity to the liquid in the cells, notwithstanding the amalgama- 
tion of the zinc, there was local action enough upon that metal to disengage hydro- 
gen ; which, in however small a quantity, was sufficient to commence the precipitation 
of the copper upon it. Single circles were thus immediately formed by the two metals, 
and local action increased to such a degree as speedily to cover the zinc with reduced 
copper. The addition of nitrate of mercury is not liable to the same objection ; and 
when I made use of this salt in the cells, the platinum plates soon became covered with 
metallic mercury in such quantities as ultimately to fall from them in drops. I did 
not carry this experiment far enough to ascertain whether the oxide of zinc would 
ultimately have become reduced with the oxide of mercury : but on one occasion, when 
some oxide of copper was present, the platinum plate became incrusted with a beau- 
tiful white soft amalgam ; which upon analysis proved to be an amalgam of copper. 
Notwithstanding the unfavourable effect upon the circulating force of this second- 
ary deoxidating power of the nascent hydrogen, where the ultimate result is the de- 
position of a solid body having a strong affinity for the oxygen of the electrolyte, 
there can be no doubt that the removal of the hydrogen by combinations which do 
not give rise to such precipitation greatly promotes the efficiency of the current : and 
I have had abundant opportunities of confirming your explanation of the good effects 
of the addition of nitric acid to the battery-charge by its abstraction of the hydrogen *. 
It is, moreover, quite certain, that not only does the oxygen of the acid act in this 
way as a dehydrogenating agent, but the nitrogen also ; for by neutralizing the ex- 
hausted charge of one of the cells of the battery with carbonate of soda, I not only 
obtained abundance of ammonia by distillation with lime, but a copious precipitate 
of ammonio-muriate of platinum with a solution of the chloride of that metal. 
Having thus detailed, I hope sufficiently, the progressive steps by which I was led 
to the discovery of the cause of the variations and decline of the force of the voltaic 
battery, as well as of certain principles upon the application of which I have relied 
for the counteraction of its injurious effects, I will not detain you with any account 
of the less successful attempts which I made for that purpose, but proceed at once to 
describe a voltaic combination which I trust you will think worthy of the name of the 
Constant Battery. 
Fig. 1. of Plate IX. represents a section of one of the cells, ten of which are shown 
* Experimental Researches (1021.). 
