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effect of borax during smelting (6 replies and 1 comment)

3 months ago
applelab 3 months ago

i read that borax (flux) reduce the melting temperature of gold during smelting. How is this so? Thanx.

3 months ago
jpearcy 3 months ago
1 like by David

Borax and lime are used as flux agents in the cupellation process to separate silver and gold from base metals and other impurities. The process is carried out at temperatures between 800 and 900°C, i.e. lower than the melting point of the noble metals, and even below the temperature at which the slag becomes totally molten. Base metals are oxidized and removed with the slag, while gold and silver, which do not oxidize, sink and build up, leading to doré bars for further partitioning and refining. This process would only be economical if silver and/or gold are pre-concentrated first, as it is the case in anode slimes from copper electrolytic refining.

3 months ago

thank you

3 months ago
GeoffC 3 months ago
1 like by David

Borax along with other flux reagents form a slag to remove impurities during smelting. This usually takes place at lower temperatures than the melting of dore. A presentation from Trainor in 1986 explains a lot of what happens during smelting.

3 months ago
David 3 months ago
3 months ago
Bhaduri 3 months ago

A free copy of "A textbook of Fire Assaying", by Bugbee (1922), is available on the web; this tome encapsulates the fusion reactions occurring during smelting of PM ores in the presence of multiple fluxes including borax.

2 months ago
kannan 2 months ago

Is any other flux available for smelting low grade gold. 

How to improve the smelting yield?


2 months ago
dhaefi 2 months ago

how we can we determine the concentrate of borax that is use to burning gold ore

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