Acid testing question

[CaptainMorganNC]

I am sorry to have to ask this, but I did search the forums and all over the internet, but did not find my answer. I have an acid gold testing set. I have a small nugget (3 grams) of gold that I made from recovered gold from a computer. To recover the gold I used hydrochloric acid acid and hydrogen peroxide.

I tested the gold two different ways. I made a mark on the stone and I applied directly to the nugget. When I use 22k acid on the stone it very slowly goes away (like 5 min). I use 18k acid and it goes away slower. When I apply acid the nugget I can leave it there all day and does not seem to do anything. Where my questions come in is that when I wipe the acid off the acid is green, but not the gold. Also whipping the acid off of the stone removes the gold too. What do you experienced people make of this?

I did have it tested at a jewelry store and they acid tested it at 18k, but said that they did not have any higher acids.

I sold the nugget and the person said that his GLX 24 Pro gold tester said 12K. I appreciate any help that you can give me.

Should the gold come off the stone if the acid did not dissolve it?

Should the acid be green after testing?

 

[BosnMate]

I don't know, but I'm posting here to make it easier to watch this post, because I'm also interested in what you find out.

 

[Geriatric_Silverback]

What was the lowest acid that actually changed anything? What intermediate acids below 18K do you have in your kit? If the other guy's kit goes from 18K down to 12k, it could possibly be that he is trying to get the better value. By the way 18K slowly affects it, I'd say it is near 18K rather than 12K. Just my opinion...

 

[CaptainMorganNC]

I have all the way down to 10k. It really does not seem to care what acid you put on it besides what I have already posted.

 

[Plumbata]

If it's the brown acid, I recommend against testing it.

 

[rampuffpuff]

Hi, and I hope this helps. Gold test solutions for the most part are actually Aqua Regia, so on your stone even 24 k will slowly dissolve som

Being very familiar with gold recovery methods what I can tell from your discription is that there was some CuCl in your solution before the drop and Cu was carried down with the Au. This would happen regardless of your reagent, but more so if dropping with bisulfates or sulfate based reagents.

18 k seems to be the average test point for drops with Cu in them. HCl and peroxide solutions will definately carry base metals and Cu along with them. You need to do more to get rid of these other metals before dissolving the gold.

 

[rampuffpuff]

Ps: make sure you wash the precipitate good. Wash with heated hcl sevral times, rinsing with distilled water in between, and also wash eith ammonia (unscented) which will dissolve CuCl and leave behind the gold. Visit a forum for gold refining of same name and be pepared to hear " did you read Holke's book yet?".

Good luck.

PPs: there may also be traces of silver and PGMs in your solution. As long as you didn't use HNO3 there is no danger using ammonia, but if you did be careful because ammonia and silver chlorides and nitrates could create a very powerful and unstable explosive which could either ruin your workshop and body parts, or bring down the feds for creating TAP which is a favorite for terrorists creating IEDs.

 

[rampuffpuff]

There are many dangerous compounds which can be inadvertently formed when refining precious metals. LEARN THEM ALL, and learn which chemicals to keep out of your inventory, toluene for example, which is a main ingredient for meth productiin. Last thing you need is to have all the same raw materials as a meth lab... and no they will bust you anyways even when you say you are only refining gold.

75% of your chemistry research should be about prevention, if not more.