Nitric digestion

[Strikeitrich]

Hi all,

This question has kinda been gnawing at me for a while, but I couldn't find an answer. Why do we have to inquart low carat gold to 6k before nitric digestion? I would think at least that Nitric digestion would have the same effect on all gold no matter the percentage, and that only the base metals would be dissolved.

 

[jimdoc]

Harold explains it best;

http://goldrefiningforum.com/phpBB3/viewtopic.php?f=48&t=11945&p=121320&hilit=why+inquart#p121320

A simple search for; why inquart
Then look for a post by Harold, but I am sure it has been explained by others as well.

Jim

 

[qst42know]

There are two reasons to inquart.

One to reduce the gold content so the silver can be leached away.

The other is to collect platinum and palladium with the silver so you can drop clean gold.

 

[Harold_V]

Hi all,

This question has kinda been gnawing at me for a while, but I couldn't find an answer. Why do we have to inquart low carat gold to 6k before nitric digestion? I would think at least that Nitric digestion would have the same effect on all gold no matter the percentage, and that only the base metals would be dissolved.

The presence of excessive gold (greater than about 40%) protects the base metals from dissolution by isolating them with its presence. The 25% figure allows for the base metal/silver to be fully dissolved without breaking down the gold to fine particles, which would then yield issues with separating the solids from the solution. At the 40% gold ratio, base metals are removed only with considerable difficulty, and, in heavy cross sections, not completely.

Harold

 

[nickvc]

To fry your brain a little more high karat gold will dissolve easily in AR but lower karat material 9/10 karat can stubbornly refuse to dissolve due to the alloy make up which can contain 10-50% silver which forms a barrier of silver chloride which stops the gold been dissolved.
This is another reason why inquartation is the recommended method for karat scrap for the home or small refiner the nitric removes virtually all the base metals, silver and PGMs if any is in the mix allowing a very clean material for refining and allowing the recovery of all values in the scrap.