RECENT PROGRESS IN PHYSICS. 399 



to a metal, and vice versa the more readily this metal is acted iipon by 

 the fluid. In the case given the metal immersed in the solution of 

 gold is more easily attacked than the gold itself; as long, therefore, as 

 the immersed part is not entirely gilded, the current will seek the 

 points in the metal to be gilded which are still uncovered, and will 

 deposit gold upon them, whatever may be the length of the path it has 

 to traverse through the liquid, i. e., however irregular the form of the 

 object to be coated." The objects to be gilded had a clean metallic 

 surface given to them, and remained after the gilding either malt or 

 polished, as they had been before. The gilding thus produced by De 

 la Rive was therefore in all cases only thin ; he gave no quantitative 

 indications either of the force of current or of the weight of the gold 

 precipitated. At first De la Rive gilded directly only silver and brass; 

 iron had to be previously coated with copper. Bottger repeated these 

 experiments with a solution of gold as nearly neutral as possible, and 

 thought that he observed a reddening of the ol3Ject wlien the conducting 

 copper wire was immersed in the solution of gold. He says tbat copper 

 cannot be gilded at all when the solution of gold contains even but 

 traces of copper; then copper only can be precipitated, and De la Rive, 

 according to him, must be mistaken in his statement of the necessity 

 of previously coppering iron objects ; he succeeded very well in gilding 

 steel pens, &c., withou-t the use of copper. — (Dingler's Journal, vol. 

 78; Frankfurter Gewerbefreund fur 1840, No. 10.) With chloride of 

 platinum objects can in the same manner be thinly platinized. 

 Bottger considers 5 to 6 immersions of one minute each sufficient for 

 a strong gilding. 



Iron can certainly be lightly gilded with chloride of gold without 

 previously being coated with copper, and Arago laid before the academy 

 a watch-spring gilded by Dent (Dingler's Journal, voh 80, p. 399, 

 Compt. Rend., vol. 12, 1841, p. 779,) and stated that a Mr. Perrot, at 

 Rouen, had previously already done the same thing, but would not 

 present it to the academy before he had gilded an entire watch while 

 it was going ! But the gilding and silvering process only became prac- 

 tically useful after the employment of the cyanogen compounds. Elk- 

 ington had a manufactory of jewelry at Birmingham, where the gilding 

 and silvering were done by immersion, and where also experiments 

 were made in gilding with chloride of gold by means of galvanism. 

 But when John Wright, a surgeon, had made use of the compounds 

 of cyanogen, Elkington at once understood the great importance of the 

 matter, and bought the right of this invention to incorporate it in the 

 specification of his process of gilding, for which he had just applied 

 for a patent. In France, also, he procured a patent, and there had to 

 compete with Von Ruolz, whose patent was of an earlier date by some 

 days. Afterwards they ibrmed a partnership. 



Elkington always employed a separate decomposing cell, and used 

 for gilding either three pounds cyanide of potassium, ten pounds of 

 water, and five ounces of oxide of gold, or two pounds cyanide of 

 potassium, ten pounds of water, and two ounces of oxide of gold ; 

 thick coatings in this process became matt, and had to be scoured with, 

 a wire brush. Iron had to be coppered ; for this purpose it was placed 



