MM. St.-Claire Deville and Caron on Magnesium. 53 
The reducing action exercised by arsenious acid on silver and 
copper in the presence of alkalies, extends also to some nitro- 
compounds *. When nitrobenzole is digested with solution of ar- 
senious acid in excess of strong caustic soda, it is converted into 
aniline, which can be distilled off and obtained pure. Wohler 
intends trying this reducing action on other nitro-compounds. 
St.-Clair Deville and Caron+ have investigated the preparation 
and properties of magnesium. A mixture is made of chlorides of 
magnesium and sodium with fluoride of calcium, to this mixture 
sodium in pieces is added, and the whole mixed well together. 
This mixture is then introduced into a red-hot earthen crucible, 
which is closed down. The action commences immediately, and 
when it is over, the lid is removed, and the mass stirred well 
with an iren rod until the mixture is quite uniform. It is then 
allowed to cool, and when about to solidify is poured out on an 
iron plate; this mass, when cold, is broken up and the globules 
of magnesium picked out. The rest of the mass can be remelted, 
and more magnesium obtained. Wohler{ recommends that the 
mixture be allowed to become cold in the crucible, which is then 
broken and the globules separated from the adhering scoria by 
solution in water. They may be obtained much brighter by 
immersing them in a solution of sal-ammoniac, or of carbonate 
of soda, but must not be allowed to remain too long, as they dis- 
solve with evolution of hydrogen. They are then washea and 
carefully dried at a gentle heat. Wohler succeeded in preparing 
magnesium by the reduction of the double salt of chloride of 
magnesium and sodium, obtained by mixing the solutions of the 
two chlorides in equivalent proportions, evaporating them to 
dryness, and fusing the mass. 
To purify crude magnesium, it is heated in a tube of dense 
gas coke to an almost white heat, and a slow stream of hydrogen 
passed through ; on cooling, the metal is taken out, and melted 
under a mixture of chloride of magnesium, chloride of sodium, 
and fluoride of calcium. By increasing the proportion of the 
fluoride, the mixture is rendered less fusible than magnesium, 
so that the latter can be poured off at the moment at which the 
former solidifies. 
Magnesium is volatile like zinc, and at almost the same tem- 
perature as that metal. When pure it volatilizes without leaving 
any residue, and the sublimed metal is white and coated with a 
small quantity of magnesia. Magnesium has about the same 
melting-point as zinc; heated somewhat higher it ignites and 
* Liebig’s Annalen, April 1857. 
+ Comptes Rendus, February 23, 1857. 
t Liebig’s Annalen, March 1857. 
