LONG-CONTINUED ELECTRIC CURRENTS OF LOW TENSION. 
45 
of hydrogen are disengaged from the amalgamated wire, which soon cease, and in an 
hour or two, a leaden grey spongy mass is observed adhering to the wire, which is 
sometimes sufficiently bulky to fill the tube, and putting on much of the external ap- 
pearance of a mass of cellular galena. This mass consists of a spongy amalgam of 
ammonium, containing a very minute proportion of mercury; it is lighter than the 
solution in which it is immersed, for on adroitly separating a portion of it, it rises to 
the surface and rapidly decomposes water, hydrogen being evolved and ammonia 
formed. 
19. It is a very curious and interesting fact, that although this spongy ammoniacal 
amalgam cannot be kept immersed in water even for a few instants without the for- 
mation of ammonia, yet as long as it is connected with the negative electrode of the 
battery, it may be preserved without change for days and weeks. The instant the 
connexion with the battery is broken, a mass of this amalgam, as large as a walnut, 
appears to vanish in a few seconds, torrents of minute bubbles being given off, and a 
scarcely appreciable quantity of mercury being left on the wire. On again closing 
the connexion with the battery decomposition recommences, and the amalgam is re- 
produced. 
20. From a review of the results of these experiments, we cannot help being struck 
with the very energetic power of electric currents of weak tension ; currents of suffi- 
cient energy to reduce to the metallic state oxides on which currents of higher ten- 
sion from large batteries are comparatively powerless. This fact, although pointed 
out by Becquerel and other philosophers, has (as far as I am aware) never been 
before shown to hold good in the reduction of the alkaline metals. Potassium and 
ammonium not having, I believe, been previously obtained by the weak current ema- 
nating from the chemical action of saline solutions on a single pair of plates ; and 
silicon, although obtained by Becquerel combined with iron, has not been procured 
before in a pure state by electric currents, at least by those of feeble tension *. 
In conclusion I may be permitted to observe, that in applying weak electric cur- 
rents to the reduction of metallic oxides, it is absolutely necessary that a continuous 
current be employed, and that its cessation even for an instant is of ten fatal to the suc- 
cess of the experiment on hand, which cessation or suspension, as far as my experi- 
ments have gone, the modification I have proposed of Professor Daniells battery 
appears to be capable of obviating. 
Guy s Hospital, 
January 20, 1837- 
* Some other curious circumstances connected with the decomposing electro-chemical power of currents of 
low tension have fallen under my observation, hut have not yet been sufficiently examined to authorize their 
publication as facts. Some of these I may perhaps at a future period, with the permission of the Society, 
have the honour of submitting to its notice. 
