of Silver into Gold. 21 



ahafty vleWj one might conclude, that the gold which is af- 

 terwards found in the fame filver, when revived from horn- 

 filver, could not be a portion of the fame gold of which a part 

 had been depofited on the firft folulion of the impure filvcr. 

 But is it not poflible that even when the folution has fiuod a 

 confiderable time, and the greater part of the gold powder 

 has depofited itfelf, a portion may ftill remain fufpOnded, 

 and its particles be fo minute as to pafs through the filtre ? 

 A well diluted fomewhat ferruginous acid, after diluted 

 prufliat of potafli (phlogifticated alkali) has been added to 

 it, looks at firll blue, but perfeftly tranfparent ; yet in the 

 courfe of a few days real Pruflian blue depofits itfelf at the 

 bottom as a fine powder, and then the fluid lofes its colour. 

 The particles of the precipitate are at firft too fine, and ap- 

 pear under too fmall angles, to be diitinguifhed by the eye as 

 folid bodies amidft the fluid. The caf- is the f;ime with 

 filiceous earth, when the liquor of flints is much diluted ; 

 and alfo with gold calx precipitated with the mineral alkali 

 from aqua regia, where the tranfparent colourlels ley poured 

 off" from the firft precipitate, and filtred through eight folds of 

 paper, at the end of feveral days again forms a black dcpofit. 

 As my time is fully occupied with the procefles neceflary 

 for my Le6tures, I have not leifurc at prefent to examine this 

 clrcumftance by a feries of experiments. But, perhaps, 

 fomc other chemift, by repeatedly difl'olving fiber and pre- 

 cipitating it by muriatic fait, may be enabled to confirm or 

 refute my opinion. 



OhftTvalions on the foregoing Paper, by Dr. Sen ERE R. 



THE preceding remarks are greatly confirmed by many 

 obfervations already made public. Thus Homberg, in fup- 

 port of his aflcrtion that all gold has been once filver, (piotcs 

 tlie following experiments : " If you fufe a hundred times 

 in fucceflion 8 or 16 ounces of filver, which, by previous 

 quartation, you are convinced contains no gold, keeping it 

 each time at leait an hour in fufion, and afterwards feparate 

 C3 it 



