Fluid Galvanic Battery. 265 



by dissolving nearly two pounds of salt in each gallon of 

 water. 



It will be very useful to dissolve some carbonate or sulphate 

 of soda in each of these exciting fluids, except the last. I recom- 

 mend the last in preference to any of the others : first, because 

 it is the cheapest of all ; secondly, because I think the amalga- 

 mated surface of the zinc is better preserved, and kept cleaner 

 by the last than by any of the others ; thirdly, because it appears 

 to act less on amalgamated zinc than any of the others. 



A very powerful battery may be made by exciting amalga- 

 mated zinc, and iron, copper, platina, or a platinized metal with 

 any of these fluids. But they produce the greatest galvanic 

 power when cast iron is the negative element. 



Muriatic acid preserves the amalgam on the zinc, but it soon 

 covers it with a dark scum, which I fear would, after some time, 

 diminish the action of the battery. Besides, it acts more than 

 dilute sulphuric acid on amalgamated zinc. One would expect 

 that sulphuric acid mixed with a solution of common salt would 

 have the same effect as muriatic acid on the zinc; but such is 

 not the case. 



On account of its powerful galvanic action, a cast-iron battery 

 charged with any of the above-mentioned fluids generates a large 

 quantity of hydrogen, which produces considerable effervescence 

 at the top of the cells. To obviate this inconvenience, I mixed 

 with the exciting fluids various metallic and alkaline salts, hoping 

 that the oxygen set free might combine with the liberated hy 

 drogen, as it does in Daniell's and in the nitric acid batteries ; 

 and that some of them which contained the same proportion of 

 oxygen as the nitrates do, might, like them when dissolved in 

 sulphuric acid, give an increase of voltaic power. But my hopes 

 were disappointed. The salts which I used principally were 

 sulphate of iron and copper, acetate of lead, phosphate of soda, 

 chlorate, arseniate and permanganate of potash. The efferves- 

 cence appeared to be somewhat diminished by acetate of lead and 

 phosphate of soda. Sulphate of copper and arseniate of potash 

 produced a slight increase of voltaic power; but when sulphate 

 of copper was used, copper was soon deposited on the zinc plate. 

 Chlorate of potash, as might be expected, caused a series of ex- 

 plosions in the cell. There was no beneficial result from the use 

 of permanganate of potash or peroxide of lead. On the whole, 

 the effect produced by these substances would not be worth 

 their cost. 



In making a cast-iron battery to be excited by any of the 

 fluids which I have described, care must be taken first to have 

 the east iron and zinc very near to each other; and secondly, to 

 protect the inactive part of the cast iron against the action of the 



