SILVER AND GOLD PLATING. 151 



M. Koseleur recommends the use of two baths; one for 

 gilding hot the small articles, the other for gilding cold the 

 large objects. 



1. Cold Process Gilding Solution. 



Distilled water 10 litres. 



Pure potassic cyanide 200 grammes. 



Virgin gold .. 100 ., 



The virgin gold, transformed into chloride, is dissolved in 

 2 litres and the cyanide in 8 litres of water. The two solutions 

 are mixed, which discolours them, and boiled for 30 minutes. 

 The effectiveness of the solution is maintained by adding equal 

 quantities of pure potassic cyanide and auric chloride, a few 

 grammes at a time; if the solution is too rich in gold the 

 deposit is blackish or dark ; if it contains an excess of cyanide, 

 the gilding is slow and the deposit grey. 



2. Hot Process Gilding Solution. 



Sodic phosphate, crystallised 600 grammes. 



Sodic bisulphite 100 



Pure potassic cyanide 10 litres. 



Virgin gold transformed into chloride . . 10 litres. 



Dissolve the sodic phosphate in 8 litres of hot water, let 

 the auric chloride cool in 1 litre of water ; mix gradually the 

 second solution with the first one : dissolve the cyanide and 

 the bisulphite in one litre of water and mix this last solution 

 with the two others. This bath can be used at a temperature 

 varying from 50 to 80 Centigrade. 



For dissolving gold in aqua regia the gold as well as the 

 hydrochloric and nitric acids must be pure. 



PREPARATION OF ARTICLES FOR GOLD-PLATING. The 

 articles for gilding must be prepared in the same manner as 

 those for silvering ; that is to say, must be previously cleansed, 

 pickled, then scoured in a preparatory bath and in the brighten- 

 ing bath, and lastly amalgamated, without forgetting of course 

 the vigorous and numerous lixiviations which follow each of 

 these operations. 



Copper, brass, and generally all the cupric alloys can be 

 directly gilded without a previous amalgamation. 



