42 
MR. BIRD ON THE ELECTRO-CHEMICAL INFLUENCE OF 
applied to the platinum, that portion of the crust more in contact with the fluid being 
generally black, and frequently covered with a layer of the hydrated and gelatinous 
green oxide. 
11. Finding that by means of this apparatus I could command a weak but conti- 
nuous current capable of reducing even the more refractory metallic oxides, I was 
anxious to ascertain whether the current was sufficiently energetic to cause the re- 
duction of those oxides which (as silica) do not yield to powerful batteries, and which 
M. Becquerel obtained only alloyed with iron. 
12. The solution of silicon used by M. Becquerel was prepared by dissolving gela- 
tinous silicic acid in hydrochloric acid of commerce, which always contains iron; 
this on being submitted to the action of a single pair of plates deposited an alloy of 
iron and silicon on the negative electrode. As this solution contains but a very small 
quantity of silicon, I substituted a solution of fluoride of silicon in alcohol obtained 
by passing a current of the gaseous fluoride into strong alcohol. On filling the 
smaller tube of the decomposing apparatus (7.) with this solution, and making the 
connexion with the battery in the manner already described, bubbles of hydrogen 
were copiously evolved at the surface of the platinum plate (negative electrode), 
which continued for eight or ten hours, when the platinum appeared to be tarnished, 
and in twenty-four hours a copious deposit of silicon had taken place on the platinum, 
to the surface of which it firmly adhered. Around the reduced silicon, and suspended 
in the fluid, was a dense gelatinous cloud of silicic acid. On quickly withdrawing 
the slip of platinum, dipping it in water, and then pressing it between folds of bibu- 
lous paper it was dried, and freed from any adhering solution. The silicon was 
nearly black and granular, under a lens, exhibiting a tendency to a crystalline form. 
It was not deposited on the platinum in a confused or irregular manner, but in lon- 
gitudinal striae, which appeared to follow the direction of certain lines of minute 
eminences on the surface of the piece of platinum, produced apparently by scouring 
it with fine sand and a piece of cork before being used for the construction of the 
negative electrode. 
13. The silicon thus procured becomes of a snowy whiteness when ignited in the 
flame of a spirit lamp, and falls off the platinum in thin flakes, being in fact converted 
into silicic acid. It is not very easy to oxidate the whole, in consequence of the flakes 
of the acid forming an incrustation over the subjacent silicon, and protecting it from 
the oxidating influence of the air even at a red heat. A portion of the silicon re- 
moved l from the platinum did not appear to dissolve in hydrochloric acid ; but when 
the platinum itself with the firmly adhering silicon was immersed in the acid, slow 
action ensued, bubbles of hydrogen being evolved from the exposed surface of pla- 
tinum, the silicon very slowly disappearing ; the solution being probably occasioned 
by the formation of a simple voltaic circle, the silicon and platinum being the metals, 
and the acid the exciting fluid. When an aqueous solution of hydrofluosilicic acid is 
substituted for the fluoride of silicon, the metalloid is reduced, but slower and in 
