Same gold drop, two different shades.

[tesremos]

okay dokay,

so i was cleaning up, --ish

i gathered my filters i'd used from stripping cell, and from filtering ap solution off foils, and incinerated them,


then proceeded to boil in HCl, rinse, Repeat,

and then pooor mans AR, HCl (290gr/L) with potassium nitrate, *very small additions until no reaction*

this has been successful on the last time i cleaned up all my filters,

but this time,

after i filtered, and added SMB

something strange happened.


Can any one explain this?

i can elaborate more on my procedure.
but ive never seen gold drop as two different shades in the one drop before.

 

[ilikesilver]

Im NOT SURE on this but it almost looks like drag down of another metal still in the fluid?? some sort of contamination maybe

 

[g_axelsson]

Did you deNOx the solution before trying to drop the gold?

I think I've seen something similar from a solution I had to fight the nitric acid. At first the drop went well and a layer of pale gold formed on the bottom, but then some of it went into solution again and precipitated later as a dark layer of gold. Sorry, I don't remember any more details than that.
Usually I get darker gold when dropping from dirty solutions or very diluted ones. I don't worry about the color that much as I'm going to refine it all a second time when I have accumulated enough powder. Actually, that is what I'm doing today and I'm almost done dissolving 52 grams of gold. :mrgreen:

I wouldn't worry too much but I would do a second refining of that gold unless you are just going to sell it to a refinery anyhow.

Göran

 

[tesremos]

Yeup complety De-NOxx'd


so on closer inspection in daylight today, it appears the dark color is caused by gold particles. big chunky ones... sitting on top of a layer of SO2


i gave it a stir and presto, bright shiny yellow powder


it was still very weird and cool to see the two colors deposited on the bottom tho... i wanna try replicate it.

 

[Palladium]

Did you deNOx the solution before trying to drop the gold?

I think I've seen something similar from a solution I had to fight the nitric acid. At first the drop went well and a layer of pale gold formed on the bottom, but then some of it went into solution again and precipitated later as a dark layer of gold. Sorry, I don't remember any more details than that.
Usually I get darker gold when dropping from dirty solutions or very diluted ones. I don't worry about the color that much as I'm going to refine it all a second time when I have accumulated enough powder. Actually, that is what I'm doing today and I'm almost done dissolving 52 grams of gold. :mrgreen:

I wouldn't worry too much but I would do a second refining of that gold unless you are just going to sell it to a refinery anyhow.

Göran

What he said !

Did you use a lot of smb?

 

[tesremos]

about 1 teaspoon

so no not alot,


on to washing it and then re dissolution,


funny tho, for such a dirty solution, its come up very pale and pretty tan coloured with out washing it,

 

[NobleMetalWorks]

If you are making small additions of HNO3, you do not need to de-nox later because you are only using as much as needed to dissolve the metals.

You should also be expanding your solution by an addition of DI water before precipitating.

Scott

 

[Geo]

during the chemical process of the SO2 precipitating gold, the first part of the drop is cleaner than the last part. "drag down" is a mechanical action that happens near the end of the drop. the first part of the drop being cleaner will be a lighter color while the later part of the drop will be contaminated with copper and be a darker color. not sure thats whats going on but it sure looks like it.

 

[tesremos]

ive made the mistake of too much NOxx before


ive learnt to small additions,

but i stil check to see if there is NOxx left over.

i heat solution before i drop with smb, and add a prill of urea. if mass fizzing, ive made a mistake and need to de NOxx

mostly ive done well and not had to.

a question, kinda off topic,

the ammonia wash.


im in a habit of keeping all my liquids,

is the ammonia wash safe to go in same liquid container as the HCl washes?

im guessing not, and it should be put in its own separate container?

 

[Geo]

keep ammonia wash separate and be sure to acidify the solution when washing is complete. you can use hcl or even vinegar.

 

[Palladium]

Though color is meant as an indicator of gold purity it should not be the final authority. Remember color is dependent on the surface that it reflects from and the particle size to name a few attributes and all these are governed by the solution concentration, pollutants present, temperature, type of precipitant used, and even how fast the drop neculates.

 

[Harold_V]

a question, kinda off topic,

the ammonia wash.


im in a habit of keeping all my liquids,

is the ammonia wash safe to go in same liquid container as the HCl washes?

im guessing not, and it should be put in its own separate container?

Well, for starters, it's not off topic--it is a good and valid question. I'll give you my views. Others may have a differing opinion.

Lets start with your comment that "I'm in a habit of keeping all my liquids".

Lose that habit. You're going to find yourself hip deep in solutions, and you won't have a clue why, or if they're worth keeping. It is far more easy to discard your solutions on a daily basis, so you don't get backlogged. Do so properly, of course.
Not sure if they should be kept, or not?
Can you say stannous chloride?
If a solution tests negative, the only thing you may recover by keeping is extremely fine particles that may be very slow to settle. That's not generallly the case, however, but I make mention so it isn't overlooked.

I'm going to assume that you'd be including solutions left from the precipitation and washing of gold.

Ammonia that contains dissolved silver offers the risk of becoming unstable (explosive) once dried. You can avoid that by combing the ammonia with the left over solution we just talked about. After all, it's most likely highly acidic, and of no value. If the ammonia contains silver, it will be precipitated as silver choride, which you can then recover.

If all else fails, why don't you keep a large stock pot (it can be an ice cream bucket, or even a five gallon pail, plastic) in which you keep scrap steel. Pour all of your waste solutions there, so that any values that may be present will be cemented. You'd recover the resulting black sludge in due time, for processing. Note that when steel is used, there's always a small amount of carbon that accumulates (from the steel). This method consumes the acid by dissolving the steel, resulting in a solution that is safe to discard because it no longer contains heavy metals.

I do not recommend you send copper solutions to this stock pot (assuming they have been tested for values). Use the same process to remove the dissolved copper, however, so you can safely discard the solution. Just don't expect to process the resulting copper for values. You may have success selling the material, although in years past that was not an option.

In regards to the previous paragraph, if you have solutions of copper that test positive for values, use pieces of copper to cement the values. It may be a slow process, but you can achieve 100% recovery. Once free of values, the copper solution would then have the copper removed with scrap steel, so it could be discarded safely.

Harold