AuCl questions

[lawsonland]

Hi,
I had some old batches AuCl sitting around for a while.

1. One gallon was a very nice deep yellow and clear when it was put into the container. I put it into a bucket to drop the gold and there was a lot of fine brown powder on the bottom.
Q. Can, does, will gold drop on its own from AuCl that has been sitting or is this something else?

2. Two gallons were from some of the first batches I ran and while it was a nice yellow color it was a cloudy yellow. I put into a bucket and added SMB to drop the gold. What dropped was very fine black material (clumps together) - I figure its dirty and will refine again. The liquid left over after siphoning has a bluish tint?. All my other batches were clear after dropping the gold.
Q. What could cause the liquid to have a bluish tint? It tested negative for PM. I will verify again. Also what is the liquid left over after the gold is dropped? The SMB drops the gold and AuCl becomes?

Thanks

 

[butcher]

Gold chloride normally will not precipitate the gold on its own from a solution even if allowed to sit a very long time,unless there is something else to replace the gold from solution, or which will reduce the gold by giving the gold ions back an electrons, but it could if there was something else dissolved with the gold, so this brown powder very well could be gold.
Some metals will also reduce back to metal from solution with bright light like sunlight (take silver chloride, or bromide in photography for example).

The blue or greenish liquid is most likely a base metal in solution,copper is the most likely suspect.

Gold chloride mixed with sodium metabisulfite, the byproducts of the reaction is basically sodium sulfate with water, there can be residual acid chlorides and base metals.

 

[lazersteve]

I have seen gold powder 'spontaneously' precipitate when the pregnant solution is diluted.

I have also seen gold do this when the container I add the gold solution to had recently been used for precipitation. I believe this is due to the fact that the container traps some of the reducing agent (SO2) in or on the walls of the container. Remember that plastic and glass have porous structures that can trap molecules.

Steve

 

[lawsonland]

Hi
Thanks for the replies.
I learned a lot from the forum and practice since I made these batches. I had bottled them then because I was still learning and figured as I got more experience I could redo it.

I recovered what was in he containers, its a lot darker than my recent batches and will clean and refine again.

Heres what I got, .

 

[goldsilverpro]

This is off the subject. On most beakers, erlenmeyer flasks, etc., there is a large white square designed for labeling. I noticed you have written on it with a marker, which is nearly impossible to remove. When labeling glassware, it is best to use a pencil. It holds up to most all chemicals and you can simply erase it when you want to re-label the beaker for something else.

 

[lazersteve]

I use the white square to designate certain flasks and beakers for specific metals. This way I always use the gold flasks for gold, the silver flasks for silver, etc.

Steve

 

[lawsonland]

I wanted to put the dry weight on it. I didn't think to use a pencil.,I'll remember that
Thanks,

 

[Anonymous]

I use the white square to designate certain flasks and beakers for specific metals. This way I always use the gold flasks for gold, the silver flasks for silver, etc.

Steve

That's exactly how I do all my beakers, and then I add a piece of shipping tape over it so when I wash the beakers/glassware, it doesn't wash off. As for the permanent marker, it'll wash right off the white area, that's why I started putting shipping tape over it.

Kevin