white sludge in bottom of beaker what is it?

[Anonymous]

i am getting the gold from computer parts first cutting off the gold plated pins from the sound cards etc as well as cpu's i have placed them in a beaker with 70% strength nitric . over night most of the gold has seperated from the boards and a white / grey sludge has formed on the bottom of the beaker. is this lead or un dissolver silver and how do i sepperate it from the gold?

 

[dwebb210]

Silver easily dissolves in nitric acid. I believe lead will dissolve without forming a precipitate.

Tin, however, forms a white precipitate in nitric acid.

You might filter everything, rinse with water, and treat with hydrochloric acid.

The gold will not dissolve, but any precipitated tin will dissolve.

 

[butcher]

tin in nitric will be easy to tell when trying to filter, it will be slow to filter.
it is best not to have any solder in nitric solutions.

 

[machiavelli976]

i don't like zinc nitrate either. and it comes a lot along with brass pins.

 

[g_axelsson]

Probable tin, I've seen it in most pins from computers.

From Wikipedia

Further increasing the phosphorus content leads to formation of a very hard compound Cu3P (copper phosphide), resulting in a brittle form of phosphor bronze, which has a narrow range of applications.

Around 2001, the Olin Corporation developed another phosphor bronze alloy[9] comprising:

* Zinc – 9.9%
* Tin – 2.2%
* Iron – 1.9%
* Phosphorus – 0.03%
* Copper – 85.97%

Olin developed this new alloy for use in electrical and electronic connectors. When assessed in strictly metallurgical terms it is not true phosphor bronze, but a form of iron-modified tin brass.

 

[machiavelli976]

g_axelsson, cannot argue with the facts posted above but if you have made a zinc dissolving in nitric you have seen the silly compound of nitrate.