410 On the Experimental Relations [1857. 



wanting in adherence; pressure brings out the full metallic 

 lustre in every part, and in the thin places converts the colour 

 from brown to blue, being in that respect like the result with 

 pale gold-leaf, in which the silver present dominates over the 

 colour of the gold. I do not think there is phosphorus com- 

 bined with this silver ; I did not find any, and considering the 

 surface action on metals which float as films between air and 

 water, it seems improbable that it should be there. 



Hydrogen was employed to reduce some of the metals, their 

 solutions being placed in an atmosphere of the gas. The 

 action differed considerably from that of phosphorus, as might 

 be expected. Gold produced a very thin film, too thin to be 

 washed; it had a faint metallic reflexion, and transmitted a 

 slate-blue colour like the former films. Platinum chloride was 

 acted on at once ; minute spots appeared here and there on 

 the surface ; these enlarged, became rough and corrugated at 

 the middle, though brilliant at the edges, and at last formed 

 an irregular coat over the fluid ; at the part where the film 

 was flat and brilliant, it resembled that produced by the 

 electric explosion, and by transmission gave a dark grey colour. 

 Iridium required much time, and formed a crust from centres 

 like the platinum. Palladium gave an instant action, but most 

 of the reduced metal sank in a finely divided state ; a film may 

 be obtained, but it has very little adhesion. Rhodium is 

 reduced, but the film consists of floating particles, having so 

 little adhesion that it cannot be gathered up. Silver is reduced, 

 but the film is very thin and has no tenacity. 



A copper film of very beautiful character may be obtained 

 as follows in all varieties of thickness. Let a little oxide of 

 copper be dissolved in olive-oil to form a bath, and having 

 immersed some plates of glass, for which purpose microscope 

 plates 3x1 inches are very convenient, let the whole be heated 

 up to the decomposing temperature of the oil ; being left to 

 cool, and the plates then drained and washed successively in 

 camphine and alcohol, they will be found covered with a film 

 of copper, having the proper metallic lustre and colour by 

 reflexion ; and by transmission, presenting a green colour, 

 which, though generally inclining to olive, is in the thinner 

 films often more beautiful than the green presented by pressed 

 gold. 



