sodium hydroxide

[Anonymous]

Got a quick question, could sodium hydroxide be used to just recover gold silver and pd from solution? I realize they would not be refined, but I would just like to get them out of smallish runs to accumulate enough for actual refining.

Up to this point I have been running batches that yield around 1/3 gram of gold, I would like to get the mix of metals then save to at least ounce sized batches consisting of just mixed precious metals. The reason batches are small is becuase of the large amount of matrix I have to start with.

Thanks
Jim

 

[butcher]

I would use zink, or copper,

 

[arthur kierski]

from an acid solution containing gold ,pd and ag,if naoh solution is added you get at ph7 pluss a mix precipitate of these metals-----if you add hcl to this precipitate,you will form agcl(ppt) and in the solution you will have gold chloride+pd chloride-----add smb and the gold will precipitate-----them you obtain the pd-------i do this often to obtain gold from ar solutions because i do not like to do the hcl(3times)to eliminate the nitric and do not know how to act with urea(do not rely when fizzing stopped)----

 

[Anonymous]

Did I understand correctly from you statement above that all 3 metals will form precipate, would I be able to filter this out?

I am just asking because I have baught any yet and if the results will not precipate all 3 metals as metal or compound it won't work for me.

What about sodium bicarb?

Thanks
Jim

 

[arthur kierski]

from a ar solution,it is obvious that ag in the form of agcl will not make a precipitate with naoh because the agcl was held in the filter paper whem one dissolved the pms in ar----gold,pt ,pd and even rh will form a precipitate with naoh----if you are in doubt,just make a test in the liquid left after precipitating the pms----the liquid left is almost alkaline and to make a test with stanous chloride is good if you acidify with hcl

 

[Anonymous]

Thanks Arthur, I would be getting the ag and pd from nitric acid.
gold from hcl -clorox or ar.

I don't doubt you, justed wanted to make sure i understood before buying any naoh.

thanks.
jim

 

[goldsilverpro]

As you can see from the chart in the link, there is a lot of overlap in the precipitation of the various metal hydroxides. Also, the pH of precipitation is based on concentration. It was probably drawn from pure solutions and the presence of other metals and oxidizers, such as nitric acid, would make things even more unpredictable. I don't know at what pH Au and Pd precipitate, but the gold oxide that precipitates is soluble in excess NaOH.
http://www.hoffland.net/src/tks/3.xml

The whole idea is a bucket of worms. Probably every refiner in the world, myself included, has toyed with the idea of selectively dropping metal hydroxides.

As Butcher said, use copper (not zinc). All 3 metals will cement out with copper in the form of a black powder and everything else will stay in solution. If any free nitric is still present, it will be consumed by dissolving copper. After that, the metals should cement. I definitely would use buss bar for this. It makes the cemented metals easier to collect.