5G4 On the Refinage of iinderstandard Silver. [June, 



Being three annas and five pie per cent, in value, or about -Mh per 100, 

 which was found by experiment to be the mere loss on melting this 

 kind of silver. 



Frojn the 9th of October 1845, to the present time, May 1847, I 

 have refined in this manner coarse and brittle silver to the value of over 

 ten lacs of rupees=36 100,000 ; of the Jaloun silver alone there were 

 refined in 1846 Rs. 882,510 118. In one operation about Rs. 50,000 

 worth of silver, containing over 30 per 100 of lead was thus treated, and 

 the resulting ingots, though 40 to 50 dwt. worse than our standard, were 

 cured of brittleness and rendered fit for alligation for coin. 



From these numerous and large trials it results that when the salt- 

 petreing is managed in the mode I have described, the iron vessel is 

 entirely uninjured. In fact the saltpetre has become inert before it 

 touches the side or bottom of the pot. Accordingly the same pot has 

 in many instances been used more than six times over, and after this 

 has borne the average number of common meltings, as shown by the 

 official report of Mr. Casperz the melter to the mint. 



Treatment of the Scorice. 



This part of the operation is done at leisure, and on its careful and 

 precise management depends the economy of the process. 



The scoriae well mixed together may be represented as composed of 

 fused potash, oxides of copper and base metals, granules of metallic 

 silver with oxide of silver, and a minute quantity of chloride of silver. 



The mass is first bruized in iron mortars and steeped in water for 

 two days in a leaden tub, the water then drained off and replaced, and 

 this repeated a second time. The potash is thus dissolved out, the 

 mass disintegrated and rendered pulpy, and its oxide of silver reduced 

 to the metallic state. It is now in successive portions rubbed in iron 

 mortars, and sieved on fine cane or bamboo sieves floating on water in 

 the leaden tub. The pulp of oxides passes through, and nearly all the 

 silver in granules remains on the sieve. This silver only needs to be 

 melted and returned. 



The oxides, with finely divided metallic silver, metallic copper, and 

 chloride of silver, after settling to the bottom of the tub, and the water 

 decanted or syphoned off, are placed on dry tiles, which soon absorb 

 the moisture ; of this mass from 4 to 5 cwt. weight are placed in a 

 reverberatorv furnace and calcined at a low red heat for four hours. 



