10 Some Exjperiments in the Gold Bullion Assay, 



III. 



To shoiu the progress in parting : The rate at which the 

 silver is dissolved throughout the process of parting. 



Twenty-eight places prepared (Table C) each 10 grains 

 (•99984 gold) with 25 grains silver (accurately weighed), 

 copper and lead as before, and cupellation similarly 

 conducted. 



Cornets placed in platinum thimble tray and boiled in 

 large beakers. 



For 20 minutes in 42 ozs. 1st acid, by which time red 

 fumes off (one removed every two minutes). 



For 10 minutes more in 1st acid (one removed every 2 

 minutes), washed in 1st water. 



For 10 minutes in 2nd acid (one removed per 2 minutes). 



For 10 minutes in 3rd acid (one removed per 2 minutes), 

 washed in two waters. 



Each thimble, as it was removed, was washed in two 

 waters, finally all washed together and annealed. 



No. 1 could be readily unrolled, the white of silver visible 

 on the surface. 



No. 2, brittle, on being broken, a core of silver revealed. 



Nos. 3 and 4, brittle, could be readily crushed up with the 

 fingers, but no silver core. 



The progress is rendered visible in diagrams III. and lY., 

 from which it will be seen that solution proceeds very rapidly 

 at fu-st, but more slowly as the process is continued, so 

 much so that the most of the time is consumed in expelling 

 what may be called the last traces of silver. 



Whilst the process of parting extended over 50 minutes, 



At the end of the 2nd minute 16 J out of the 25 grains 

 of silver were dissolved. 



At the end of the 4th minute 22 out of the 25 grains 

 of silver were dissolved. 



At the end of the 6th minute 24J out of the 25 grains 

 of silver were dissolved. 



Forty-four minutes further boiling being required to 

 remove the remaining f of a grain. 



At the end of 20 minutes about 1-10 grain was left. 



At the end of 30 minutes about 1-20 grain was left. 



At the end of 40 minutes about 1-100 grain was left. 



At the end of 50 minutes about 1-200 grain was left, 

 which may be permitted to remain and allowed for as 

 surcharge. 



