426 M. BECQUEREL ON CHEMICAL DECOMPOSITION AND 
and have all the properties ofthe brown oxide. We shall have occasion 
elsewhere to return to this compound. 
Lime.—It is known that the solution of hydrate of lime in water 
becomes, when in contact with the air, covered with a pellicle of carbo- 
nate of lime, and that, if this solution be reduced one half by evapo- 
ration in a basin and left to cool slowly, the earth becomes crystallized 
in the form of small needles. M.Gay-Lussac has found that when the 
evaporation takes place in vacuo, the hydrate of lime is crystallized in 
regular hexahedrons. It is perfectly easy to obtain the same crystals by 
means of the pile, without operating in vacuo. Nothing more is required 
for this purpose than to pour some Seine water, which contains a cer- 
tain quantity of sulphate of lime, into the two branches of a bent tube 
(U) having its lower part filled with moist clay, and then to plunge 
into each branch a plate of platina in communication with a pile of 
fifteen pair of plates. Not only is the water decomposed, but the sulphate 
of lime also. The water in the negative branch becomes alkaline, 
thus showing that it contains lime in solution. As the operation is 
not interrupted, there arrives a certain moment when the erystalliz- 
tion of the hydrate of lime is effected. If the salt with a calcareous base 
was more abundant, the quantity of lime that would find its way into 
the negative branch of the tube could not fail to disturb the regular 
grouping of the molecules. There can be no doubt that, by this pro- 
cess, several hydrated oxides, both alkaline and earthy, may be ob- 
tained in a crystallized state. 
Action of Hydrogen on different bodies, serving as Negative Conductors ; 
Formation of Metallie Chlorides. 
When the hydrogen arrives at the negative pole, it usually contributes 
to the reduction of the oxide by instantly forming with its oxygen a por- 
tion of water, which is afterwards decomposed by the action of the cur- 
rent. If there are any elements present with which it may combine, the 
combination will undoubtedly take place, since the gas is in its nascent 
state. We shall now proceed to notice some circumstauces of this kind. 
A combination of gold and hydrogen is a thing unknown to chemistry. 
It has nevertheless been advanced by Ritter that in decomposing water 
with gold wires there was formed at the negative pole a hydruret of this 
metal. We mention this result without vouching for its accuracy. 
It has been asserted also that by the same means silver might be 
combined with hydrogen, but the fact has not been yet proved. 
Bismuth has likewise been said to combine with hydrogen when that 
metal served as a negative conductor in the decomposition of water. In 
this case the metal becomes black and is covered with a black dendritic 
substance. | 
