Pure Gold from Alloys. 165 



aurite of potash, is gradually added. A largo quantity of crystallised 

 oxalic acid is then added, so as to be in great excess, and the whole 

 is to be quickly boiled. All the gold is immediately precipitated in 

 the form of a beautiful yellow sponge, which is absolutely pure me- 

 tallic gold. All the copper is taken up by the excess of oxalic acid, 

 and may be washed out. 



Boil the sponge in pure water so long as any trace of acidity re- 

 mains, and the gold is then to be removed from the capsule, and 

 dried on filtering paper. It may be pressed into rolls, bars, or 

 thin sheets, by pressing it moderately in paper. I have made se- 

 veral useful applications of the gold sponge thus prepared, and had 

 a tooth plugged with it in October 1846, to which purpose it is well 

 adapted. 



By moderate pressure, the spongy gold becomes a solid mass, and 

 burnishes quite brilliantly. 



The jeweller or goldsmith will find spongy gold to be quite con- 

 venient when he requires it for a solder, and it is a convenient form 

 of the metal for making amalgam for fine gilding. I have used it 

 for some years in soldering platina, and prefer it to the filings or 

 gold foil for that purpose. This method of separating fine gold from 

 coarse, is very simple, and cheaper than the usual processes. It is 

 applicable in the separation of gold from ores that may be treated by 

 acids, and is vastly preferable to the methods commonly used by 

 chemists and assayers. 



When making oxide of gold for dentists' use, the chemist will find 

 that oxalic acid, added to his potassic solution, will at once recover 

 all the gold that is dissolved in an excess of the alkaline solution.* 

 Many other applications of this very simple method will occur to 

 chemists and artizans. — (American Journal of Science and Arts, 

 2d Series, vol. vi., No. 17, September 1848, p. 187.) 



2. Discovery of Tellurium in Virginia ; by C. T, Jackson, U.S. 



G.S. 



Early in May last, Mr Knowles Taylor of New York, gave me 

 two specimens of native gold, in mica slate rock, from an auriferous 

 vein recently discovered in Whitehall, near Fredericksburg, Va. In 

 one of the specimens I observed a considerable mass of splendent 

 foliated and sectile mineral of the colour of antimony, which I re- 

 cognised as an ore of tellurium. The gold was imbedded in a mass 

 of it, and it was also observed to exist disseminated through the rock 

 in shining metallic leaves. On submitting this mineral to analysis, 

 I discovered that it was a telluret of lead and gold^ or foliated tellu- 

 rium ore. In the open glass tube before the blow-pipe, telluric acid 

 sublimes and condenses in the cooler part of the tube, in a yellowish 

 white film, which melts into drops. A little greyivsh sublimate also 

 deposits, which is metallic tellurium. The residual matter, cupelled 



* Much gold is lost by the usual method of preparing the oxide. 



