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PREPARATION OF THE OXIDE OF GOLD. 
ART. XXIV,— OBSERVATIONS ON THE PREPARATION OF 
THE OXIDE OF GOLD, (AURIC ACID.) 
By L. Figuier. 
The oxide of gold is at present extensively used in the 
arts, owing to its substitution for the cyanide of gold in the 
liquids employed in electro-gilding. 'J'his has induced me 
to determine by comparative experiments which of the pro- 
cesses employed for the preparation of this oxide is that 
which ofiers the greatest advantages. Tiiree processes 
have been described. The first, proposed by J. Pelletier, 
consists in treating a solution of the chloride of gold with 
calcined magnesia, and subsequently decomposing the 
aurate of magnesia thus formed with dilute nitric acid. 
The second process, which I have described in my memoir 
on the oxides of gold, consists in decomposing a solution of 
chloride of gold with carbonate of soda and boihng. The 
amount of carbonate of soda should accurately suffice to 
saturate the acid without the liquid acquiring an alkaline 
reaction. In the third process, which I have recently pro- 
posed, the oxide of gold is obtained by treating in the cold, 
a solution of chloride of gold with chloride of barium to 
which some caustic potash has been added. A precipitate 
of aurate of baryta is formed, which is decomposed with 
nitric acid. 
With a view of comparing these three processes, I have 
determined the quantity of oxide which each is capable of 
yielding with the same weight of gold. 10 grms. of gold 
furnished by Pelletier's process 9.08 grms. oxide, well dried 
by long exposure to the air. With carbonate of soda 10 
grms. of gold yielded 10.48 of oxide ; and the same quantity 
of metal, treated with chloride of barium and potash, gave 
11.72 oxide. This last process is consequently the most 
advantageous as regards the amount of product, but it is 
