Why is precipitated gold black?

[chrundle_the_great]

If it's been asked or answered I haven't found it yet. Why does gold come out of AR black and not gold color?

 

[goldshark]

It can come out black, brown, and a couple other hues, depending on wether more than 2 metals were dissolved in the original dissolution, and what metals they are. I also don't know if you are asking about the initial black drop with SMB, with the settled powder being brown, with a pure solution, or a precipitate that may contain a variety of other metals dropping all at the same time, with a black sludge. Both can occur, which are you referring to?

 

[FrugalRefiner]

When gold is precipitated, it comes down as a very fine powder. Light reflecting off the particles goes off in every direction, so it doesn't show the characteristic color of gold. In general, the finer the precipitate, the darker the color. Impurities also play a part. The dirtier the precipitate, the blacker it can look. Once it's washed, the powder becomes purer and agglomerates into larger clusters, so the color can lighten towards a light cinnamon/tan. If you put a tiny bit on a piece of white paper, and smear it with the back of a spoon, the particles align better and the gold color will show.

I deleted your other post. Please don't double post.

Dave

 

[chrundle_the_great]

It can come out black, brown, and a couple other hues, depending on wether more than 2 metals were dissolved in the original dissolution, and what metals they are. I also don't know if you are asking about the initial black drop with SMB, with the settled powder being brown, with a pure solution, or a precipitate that may contain a variety of other metals dropping all at the same time, with a black sludge. Both can occur, which are you referring to?

Sorry for not specifying, initial drop with SMB

 

[chrundle_the_great]

When gold is precipitated, it comes down as a very fine powder. Light reflecting off the particles goes off in every direction, so it doesn't show the characteristic color of gold. In general, the finer the precipitate, the darker the color. Impurities also play a part. The dirtier the precipitate, the blacker it can look. Once it's washed, the powder becomes purer and agglomerates into larger clusters, so the color can lighten towards a light cinnamon/tan. If you put a tiny bit on a piece of white paper, and smear it with the back of a spoon, the particles align better and the gold color will show.

I deleted your other post. Please don't double

 

[chrundle_the_great]

Ope, sorry phone is being a bit glitchy

 

[Salehe Katoba]

It can come out black, brown, and a couple other hues, depending on wether more than 2 metals were dissolved in the original dissolution, and what metals they are. I also don't know if you are asking about the initial black drop with SMB, with the settled powder being brown, with a pure solution, or a precipitate that may contain a variety of other metals dropping all at the same time, with a black sludge. Both can occur, which are you referring to?

Thank 4 education

 

[Yggdrasil]

Thank 4 education

Welcome to us.

Here are some material to study:
We ask our new members to do 3 things.
1. Read C.M. Hokes book on refining jewelers scrap, it gives an easy introduction to the most important chemistry regarding refining.
It is free here on the forum: https://goldrefiningforum.com/phpBB3/viewtopic.php?f=54&t=19798
2. Then read the safety section of the forum: https://goldrefiningforum.com/forums/safety.47/
3. And then read about "Dealing with waste" in the forum: https://goldrefiningforum.com/threads/dealing-with-waste.10539/

Suggested reading:
https://goldrefiningforum.com/forums/the-library.101/
https://goldrefiningforum.com/threads/when-in-doubt-cement-it-out.30236/
https://goldrefiningforum.com/threa...le-read-this-before-you-post-about-ore.33333/


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