I 



ON SILVER» 373 



on losing this the iron in turn, or its oxide at a minimum, gives it back t© 



takes the oxigen from the silver. The following is the them vrhco- 



cold, 

 experiment. 



In a small matras heat a solution ofredsulphat of iron Proof, 

 on parted silver, a portion of the latter, will be dissolved, 

 and the sulphat will become green. Filter, add a little 

 water with salt, separate the muriat, and the filtered 

 liquor, or sulphat of iron, will be precipitated green by 

 alkalis. But if, instead of separating the silver, the fil- 

 tered liquor be kept, it will exhibit scales of metal, in 

 proportion as it cools. Now this new precipitation can- 

 not take place but by the base of the green sulphat resum- 

 ing oxigen from the silver. We shall not be surprised 

 at this result, if we recollect, that a solution of green sul- 

 phat, mixed with a solution of sulphat of silver, instantly^ 

 precipitates the metal in a shining powder. I had an 

 opportunity of observing, some time ago, that the solu- 

 tion of red sulphat could not be concentrated in a basin of 

 fine silver without giving birth to similar changes. 



Carbohat of Silver. 

 This carbonat, obtained by means of that of potash, Carbonat of 

 is of a yellowish white colour, but does not keep well, silver parts 

 grows black on exposure to the light, and gradually parts ^^^^^^^ oxigen 

 with its oxigen ; for if at the year's end very dilute nitric 

 acid be poured on it, a portion of silver in powder will 

 be separated. 



Sulphat of Silrxor, 

 If mercury be thrown into the solution of this sulphat, Sulphat de- 

 it decomposes it, and the result is a flat crystallization, composed by 

 which scarcely deviates from the level, and of course ex-."^"^***^^* 

 hil^its/none of the pleasing phenomena of the nitrat. 



Tree of Diana. /\ 



Lemery recommends, to throw mercury into a nitric ^ ^ t)* ae. 

 solution of silver considerably diluted; and he is right. 

 In little, or in great, very beautiful and very various 

 trees of Diana will be obtained without fail. Homberg 

 and Beaume, with their balls of amalgama and solution, 

 jxavc only complicated the process, and disgusted those, 



YoL. XV,— -Supplement, Eec who / 



