uo 



C Hoffmann 



first mentioned 



it. 



Baum6 first 



proposed gild- 



iijg with it. 



Attempts to 

 gild on steel 

 with it unsuc- 

 cessful. 



Causes of its 

 fiiilure. 



HISTCHT OF GOLDi 



miniate. G. Hoffmann was, I believe, the first who, in his dis= 

 sertation on the vinous vitriolic acid, made kno-wn this action 

 of ether on the solutions of gold. Baume appears to me to 

 iavc been the first v/ho proposed the use of the auriferous 

 ether for gilding watch-work. Within these few years it has 

 been announced as well fitted for gilding figures on iron and 

 steel. I shall recite here not my success, but attempts-ex- 

 tremely unsuccessful ; which render it incumbent on the au- 

 thor of this proposal to explain himself more clearly, if he 

 would render a service to the arts, and to many amateurs, who 

 complain of having lost both their gold and their labour.* 



The ether that has become coloured by standing on a solu- 

 tion loaded to the highest degree, is far from containing as 

 much gold as is requisite for gilding with success. By means 

 of a siphon with a bulb I drew oflF the colourless liquid beneath 

 the ether, and replaced it by fresh solution : thus the ether 

 becomes of a deeper colour and more loaded. On the third 

 or fourth change the appearances alter, for the auriferous ether 

 no longer swims at the top, but sinks to the bottom with the 

 weight and consistency of oil of cinnamon : on the contrary, 

 it is the nitric acid that floats, and that must be drawn off by 

 the siphon. 



Having at length well saturated the ether, and considering 

 my success as certain, I began to trace letters on polished steel, 

 some with a pen, others with a pencil ; the strokes exhibited 

 gold, as might be expected from the application of its muriate 

 to metal so easily decomposed ; but I must say, that by no 

 nieans I could contrive to give them the quantity of gold, 

 or the continuity, consistence, and lustre, that I wished. The 

 gilding vt'as very different from that of Solingen. We shall not 

 be surprized at this, if we analyze the effects of the gilding, for 

 we shall at once discover, that a single stroke of this ether ap- 

 plied on steel immediately produces four different effects, 

 three at least of which are opposite to the end proposed. — To 

 precipitate gold, to precipitate muriate of iron, to lay bare the 

 carbon of the steel, and to take oft' the polish from every point 

 touched, are the effects produced. 



* Prof. Proust certainly had not seen Mr, Stodart's description 

 of the process, Philosophical Journal, vol. Xi. p. 215, as ^appears 

 from- the account he gives of bis own. T. 



It 



