# Enormous quantity of urea for nitric acid neutralization



## Renaldas (Sep 25, 2009)

I'm refining gold using AR, neutralizing nitric with carbamide and precipitating gold with copperas. I need to use enormous quantity of carbamide to let copperas do it's work. It's about in 1:10 ratio, maybe 1:20, if I used 5 gr of nitric, it will be necessary about 50-100 gr of carbamide. Interesting is that fizzing of AR when I put in carbamide stops after a very little quantity, but if i try to precipitate gold with copperas, nothing happens, copperas produce a slight fizzing. I should add very large amount of carbamide even my solution do not fizz. Is it normal, or there are some things I do wrong? What should be a ratio of AR (nitric acid):carbamide for full neutralization to occur?


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## butcher (Sep 25, 2009)

I don't like using urea, seems troublesome to me, may use some for certain things but, I feel evaporating off the nitric works much better.and adding small amount of gold as harold has showed us works great.
heat solution to evaporate but not boil, till almost syrup,but not till it crystalizes, add small amount HCL, I repeat this two more times, before diluting with water for using the precipitant.

as GSP taught use less nitric is very helpful, using only what is nessasary to disolve the metals, I think we seem to use more acids than we need most of the time.

if you still want to use urea, add till no fizz even in heated solution PH >1.

I think If you look into these suggestions Less nitric, evaporation and using gold button, many of your troubles will be behind you, look for Harold's and GSP's post's on this, it has really helped me.

could figure ratio's but not knowing exactly how much nitric and many other factors of your batch it would not do much good.


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## goldsilverpro (Sep 26, 2009)

I would try one of the sulfite chemicals, such as sodium sulfite or SMB, instead of the ferrous sulfate.


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## teabone (Sep 27, 2009)

GSP is right on about using sulfite instead of copperas as your precipitant. I've been using urea for many years to neutalize ar solutions because it is impractical to boil down gallons of solutions. Its much faster and no problems with gold purity as long as you follow good wash procedures.
I've noticed that copperas doesn't work well with urea neutralization,however, smb works just fine. For some reason it takes much more urea if you use copperas as your precipitant. Maybe one of the resident chemists could shed some light on the reason behind this.


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