12M HCl solution question

[LeftyTheBandit]

Greetings All;

I have 12M HCl acid.

Does this mean I must dilute my 12M HCl 12:1 with distilled water to achieve concentrated HCl acid that is used in AP?

Or do I just use 12M HCl for my AP?

Regards
Richard

 

[butcher]

I'd use it as is.

 

[LeftyTheBandit]

I looked up Molar on Wikipedia and it has something to do with concentration of acid in a solution.

During an AP batch this acid became extremely hard to filter because it became syrupy. I found it hard to keep the AP reacting even after adding fresh hydrogen peroxide.

It would explain a little bit if this 12M acid was too concentrated. But I guess if HCl is normally 12M then I should look elsewhere for my solution.

 

[Lou]

12M is quite concentrated, about as much hydrochloric acid as you can get into water.

I'd dilute it down.

 

[LeftyTheBandit]

What would the dilution ratio be with 12M HCl and distilled water?

• A) 12:1
  B) 4:1
  C) 2:1
  D) 1:1

Looking for the best ratio for standard AP process.

Regards
Richard

 

[Lou]

I'm guessing A and B are your best choices. As far as I know, the idea with AP is to have a dilute solution with very little free chlorine. This is assuming you're trying to work on pins.

If you're dissolving gold with it, in that case, use the 6M and conc. hydrogen peroxide and you'll be fine.

 

[LeftyTheBandit]

Thank you Lou.

 

[butcher]

peroxide converts to water when oxygen is removed which also helps to dilute, (38% HCl rest is water), I believe is 12molarity,(may be wrong ) I use it without dilution besides the peroxide 3%, my solutions seem dilute except for copper salts that form then need more acid , I dont understand why Lefty would have trouble? maybe not starting with enough acid solution? my volume of leaching acid to metals is very large.

(editted spelling best I could)

 

[Oz]

I have used 31.45% HCl (about 10 mole) which is standard hardware store grade. If you have 12M HCl you probably paid too much for it considering your use. I have used the 31.45% for electronics using a bubbler for the addition of oxygen. I have never found a need to dilute it, and using a bubbler instead of H2O2 I have less gold going into solution as well as less bulk of solution I must process for safe disposal when done.

 

[LeftyTheBandit]

The reason I thought the acid was too strong was that the reaction from just pouring the acid in a Pyrex measuring cup had a strong vapor released. I have watched the AP video and the reaction Steve had was almost none existent.

I'm concerned that if my acid solution is too concentrated the process will not work properly as the acid overpowers everything else. I would pour 30% hydrogen peroxide in small 50ml amounts and there was an initial reaction then the whole batch would stop cooking. No bubbles or vapor.

I let a CPU batch cook for 6 days, with 4 to 5 agitations a day, and the cpu pins still had not dissolved completely. Most of the items had 95% stripped but that last 5% was just staring at me with its tongue out.

Now I am at the HCl + Clorox stage and I'm concerned now that this 12M Acid will not act the same way as predicted with the Clorox.

I do not want to be using supercharged acids and oxidizers if I do not need too. I'm a patient fella. Im stuck with 12M acid and 32% HP, I just need to get them to the same concentration as steve had in his video so I'm not trying to re-invent the wheel.

1 part 32%HP + 10 parts water.
1 part 12M HCl + 12 parts water

Is this the dilutions I would use to have the basic AP ingredients?

 

[butcher]

I do not dilute my acids to me the stronger the better dissolves more metal, the HCl/H2O2 and or air, on cpu's takes time to disolve solder and penetrate the gold plate, warm solutions help, usually mine bubbles in air week or two depending on outdoor temps maybe longer.
(probbably unconventional but sometimes Ill give mine a prewash in HCl/bleach OR HCL/32%H2O2 prewash to cut some gold layer off to expose base metal prior to leach).
another trick I ues to finish disolving is to heat in coffee pot cpus and pins after AP (using the AP solution this loweres evaporates alot of the water concentrating it for next time making it more acidic per volume. and finishes getting the copper out of my cpu pins that the acid and air Bubbles have a hard time with.
when strong HCl added to metals they is a vapor of hydrogen released from the acid as the Cl and copper metal combine to make a copper chloride salt (blue diluted green concentrated) disolved in solution.

the Hcl/ bleach works good for me with concentrated acids.
these are slower processes than Aqua Regia, But in my opinion,less trouble and loss with precepitation. of values especially for higher base metal content of solutions, and I usually have several different types of processes goin on at same time, with plenty to do, so time soaking actually a benefit for me Its working while Im doing something else.
I wouldnt worry about gold loss with these process just save your solutions till your sure your finished reusing them ,(maybe unconventional again but I save my acid/bleach solution to disolve gold from other process batchs adding HCl & NaOCl(clorox bleach) till I'm ready to get the gold out), also let my solutions sit for days to week / 's to allow gases to disipate or somtimes using heat to speed process.
hope I am not confusing newcomers with my way of doin these and my poor ability to explain them.