REPORT ON GILDING, ETC. 
61 
the perchloride would not answer the purpose of gilding, 
and the protochloride produces the best effects ; the long 
boiling of the perchloride with bicarbonate of potassa' 
causes it to pass to the state of protochloride, on account of 
the organic matters which the bicarbonate contains. When 
the organic matters are not present, the operation only very 
difficultly succeeds ; but these matters, which are only ac- 
cidentally present, may easily be substituted by adding to 
the liquor, sulphurous acid, oxalic acid, or oxalate of pot- 
assa, which quickly reduce the perchloride of gold to the 
state of protochloride. 
The committee of the Academy considers this opinion of 
Mr. Wright to be correct, and regards the liquid to be em- 
ployed in gilding by the humid way, as essentially formed 
of a compound of protochloride of gold and chloride of pot- 
assium, dissolved in a liquid impregnated with carbonate, 
and even bicarbonate of potassa. 
The proportion of gold deposited in gilding by the humid 
way is much less considerable than by the dry way. The 
committee has ascertained that the best gilding by the hu- 
mid way fixed at the most 0.0422 gr. of gold per square de- 
cimetre, while the smallest deposition by mea^s of mercury 
fixed at least 0.0428 gr. 
3. Mr. Elkington's Galvanic Process. 
Mr. Elkington takes 31 grammes 25 centigrammes of 
gold converted into oxide, 5 hectogrammes of cyanuret of 
potassium, and 4 litres of water, and boils the whole for half 
an hour, when if is ready for use. When boiling it gilds 
very quickly, and when cold, very slowly. In both cases, 
the two poles of a constant battery are plunged into the so- 
lution, the object to be gilded being attached to the nega- 
tive pole at which the metal of the solution is deposited. 
In the experiments made by the committee, on Mr. 
Elkington's process, brass, copper, and silver were gilded. 
By this process, the thickness of the layer of gold may 
VOL. IX. NO. I. 6 
\ 
