AR

[rich_2137]

Hi all
I had around 20 grams of foils so I dissolved them in HCL-CL twice and then decided to run the powder through AR so I used 150ml of HCL and then added HN03 drop by drop, but this is where I think I've messed up as the reaction was not instant I added a few more drops!! (plus the solution was cool)
So when I've tried dropping the gold in the solution with SMB it fizzed but no drop so I added more SMB and and still no drop it's just fizzing, I'm worried I've added to much nitric and now added too much SMB
So I've now left the solution and seeking advice as I've never ran this much powder through AR
I've had no problems in the past doing the same process but I just don't want to mess it up beyond my experience!
Thanks
Rich

 

[nickvc]

Rich an easy fix is add some Sulphamic acid to kill the excess nitric and filter then add more precipitant, failing that heat the solution gently and add some fine gold to consume the nitric again filter and precipitate or the classic evaporate adding more hydrochloric to expell the nitric. Personally the first two are the quickest bit of adding more fine Au weigh it before adding to get your figure for this batch.

Edited for clarity....thanks Frugal

 

[moose7802]

Sulfamic is an easy fix and you can get it at home depot as a grout cleaner. Just make sure you check the active ingredients when you buy it. It's also best to heat your solution a little bit when adding sulfamic, it gets the free nitric active again so it can be consumed.

Whoops didn't see you where from England so you probably don't have home depot :lol: just go to a place that is DIY kinda place they should have grout cleaner

Tyler

 

[rich_2137]

Thanks Nick and thank you Tyler I have more foils so I will keep adding them until there is no more reaction, filter my solution then try with SMB again
I think I will stick with just HCL-CL next time it seems easier for me and I've had good results that way too!

Thanks guys

 

[moose7802]

The foils are definitely a good way to go.

Tyler

 

[Geo]

dont forget to heat the solution first. im with Harold on this, how people can try to refine without heating is beyond me. an observation i have made is that after the reaction from an AR dissolution has stopped (while cool), by heating the solution, the reaction will start again. acids react somewhat differently at different temperatures. they can be made to be more reactive by heating. heating serves a couple of purposes. it makes the reaction happen faster saving time and you can squeeze more action from the acids used saving resources. always remember that an AR reaction that stops reacting cool will still have free nitric.

 

[nickvc]

AR is always a problem first few times the big problem is exactly what you have done, too much nitric and not enough patience or heat, AR is always best used hot as it consumes the metals until the nitric is consumed, there's no problem over using the hydrolcloric but always be cautious with the nitric .