4^26 M. BECQUEREI, ON CHEMICAL DECOMPOSITION AND 



and have all the properties of the 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 crystalliz- 

 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 Metallic 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 circumstances 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. 



