Stock Pot solution end of life

Hi Guys!
Firstly this is for future reference. I have not done this and don't even have a stock pot yet.

This is how I believe most people use their stock pot. This stock pot should only have AP solution and base type metals in it.
Once you believe you have removed all on the PM's from the stock pot solution by adding copper. You then decant the solution to another pot and add iron to plate out the copper. You then decant that to another pot and add lime or lye to neutralize the solution to about 7pH.

From what I have read the iron dissolves into the solution and releases hydrogen.

My question is: What is the solution on the last step after adding iron but before neutralizing it? Is it still HCL?
The reason I ask is can I use a boiling flask and condenser to recover the remaining HCL acid?

By the sounds of it if there is excess water, the water will boil away first until the solution has become approximately 20% HCL acid. Then both the water and the acid will boil away and can be condensed into a flask.

Is any of this logical or am I missing something?

Thank You!
Scott

ttutone1 said:

Firstly this is for future reference.

Click to expand...

I'll provide a few comments for that purpose.

This is how I believe most people use their stock pot. This stock pot should only have AP solution and base type metals in it.
Once you believe you have removed all on the PM's from the stock pot solution by adding copper. You then decant the solution to another pot and add iron to plate out the copper. You then decant that to another pot and add lime or lye to neutralize the solution to about 7pH.

Click to expand...

I don't put old AP solution in my stock pot. Even if a bit of gold dissolved when I started a batch, it cements out on base metals long before the solution is no longer useful. I only put solutions into my stock pot if there is a chance there is some small amount of precious metals still in solution.

When you add iron, you cement out copper, but you also cement out any other metals between iron and copper in the reactivity series. This can include cadmium, cobalt, nickel, tin, lead, tungsten, antimony, arsenic, bismuth, and probably a few others if they are present in your solution.

The Dealing with Waste thread in the Library covers the neutralization process in detail, so I won't try repeat the process here.

From what I have read the iron dissolves into the solution and releases hydrogen.

My question is: What is the solution on the last step after adding iron but before neutralizing it? Is it still HCL?
The reason I ask is can I use a boiling flask and condenser to recover the remaining HCL acid?

Click to expand...

The short answer is No, it is no longer HCl. It is a combination of chlorides, including iron chlorides as well as other chlorides like perhaps zinc, aluminum, sodium, etc. which are higher on the reactivity series than iron.

By the sounds of it if there is excess water, the water will boil aay first until the solution has become approximately 20% HCL acid. Then both the water and the acid will boil away and can be condensed into a flask.

Click to expand...

I think this is a common misconception about evaporating solutions. Let's say you start with a solution that is 1% HCl. Even at room temperature, evaporation takes place. Heating speeds the process up. Regardless of the temperature, water will be evaporating at a higher rate than HCl, but a little HCl will be evaporating too. As more water evaporates, the HCl strength increases, and as it does, a bit more HCl evaporates along with the water. The closer it approaches the 20% level, the greater the amount of HCl evaporating will become. At 20%, the rates of evaporation will be equal, so if you capture and condense the evaporate, you will capture 20% HCl solution.

Understand that it's not just water evaporating until it reaches 20%.

Dave

Thank You very much FrugalRefiner!

You answered my questions and explained them very well. I very much appreciate it.

Excellent explanation!

I know there is a post around here someplace on the temps & rate of evaporation, smoking temps, boiling point of H2SO4. I can’t seem to locate it! My phone has been acting really squirrelly since I dropped it in a creek trout fishing

If memory serves me the concentration of liquid H2SO4 is 1.84 g/cm3. I could look it up, but like to bookmark all really good posts.

If you know the link please post so I can save it!

Thanks,
Rachel

Is it one of these?


http://goldrefiningforum.com/phpBB3/viewtopic.php?f=86&t=21992&p=228759&hilit=boiling+point+of+H2SO4#p228759

http://goldrefiningforum.com/phpBB3/viewtopic.php?f=49&t=13458&p=180152&hilit=boiling+point+of+H2SO4#p180152

I believe the concept of a stock pot has been bastardized somewhat. A stockpot is a container to hold solution that precious metals have been reclaimed from such as spent aqua regia. There should a separate pot for chlorides and nitrates. When you drop gold from a solution, the solution is spent but will contain trace amounts of the gold whether in solution or as suspended particles. The solution should be evaporated or rendered down to reduce volume. Then the reduced solution is added to the stock pot. Solid copper should remain in the stock pot or add a small amount of iron shavings or steel filings periodically to concentrate any values. When working with certain material, electronics is one, there should be a varying amount of PGM's in the solution. This is collected as a black powder from the stockpot and saved up to warrant a refine. A 1 gallon stock pot can hold many gallons of solution, after it has been evaporated.

Geo,

I have been a reader & admirer of yours for sooo long. I mean no offense when I ask you to use paragraphs.

It’s hard to bring together all the information you are relating in “one lump sum” lol.

What you relate is sound evidence of truth. Defining your points with paragraphs helps everyone, I.e. “take-in” the knowledge you impart.

Above all we want your knowledge imparted...not lost :wink:

Rachel

Jimdoc,

YEA BABY!!! It was by Butcher thanks for the reference!!!

Rachel