Some Experiments in the Gold Bullion Assay. 5 



who, on going over the same ground for practice, may use 

 these results for comparison with their own. The method 

 adopted was the rigorous system in use in the Melbourne 

 Mint. 



Part First. 

 EXPERIMENTAL DEMONSTRATIONS. 



To demonstrate the facts on %vhich " quartation" is based, 

 or to show the limits of the proportion of gold to silver 

 tvithin ivhich it is necessary to keep in order to part an 

 alloy of these metals, at the same time to note the colours of 

 the alloys throughout the operation. 



From the data obtained to construct the curve of " sur- 

 charge." 



Synthetical alloys of gold and silver were prepared, rang- 

 ing from an alloy containing 5 per cent, of gold up to fine 

 gold, and of the uniform weight of 35 grains each. Twenty 

 places, as detailed in Table A, were cupelled each with 

 copper disc (IJ grains) and lead case (84 grains), the 

 cupellations occupying 21 minutes. The colour and appear- 

 ance of the buttons having been noted, they were flatted, 

 annealed, rolled to the 13-1 000th of an inch in thickness, 

 annealed, and coiled according to the usual routine. The 

 parting was then conducted as foUows : — 



Nos. 1 to 5, inclusive, were parted separately in flasks. 

 Each was boiled in IJ oz. of 1st acid (sp. gr. 1.17) for ten 

 minutes beyond the time at which the red fumes cease to 

 be evolved. 



Washed with distilled water. 



Boiled for ten minutes in 1 oz. of 2nd acid (sp. gr. 1.26). 



Boiled for ten minutes in 1 oz. of 3rd acid (sp. gr. 1.3). 



Washed in two waters, transferred to crucible and an- 

 nealed. 



Nos. 6 to 20 were parted together in the 20 platinum 

 tray. 



Boiled in 22J oz. 1st acid, and for ten minutes after red 

 fumes cease. 



Washed in hot distilled water. 



Boiled for ten mjnutes in 15 oz. of 2nd acid. 



Boiled for ten minutes in 15 oz. of 3rd acid. 



Washed in two successive hot waters, and annealed. 



