I ran across a post here a while back suggesting the use of formic acid to reduce silver nitrate solution prior to copper cementation. I'm confused by this. It seems a slight excess of nitric acid is needed to dissolve the copper for the replacement reaction to proceed, so how would the reaction progress if the solution were reduced?
Formic acid reduction prior to cementation?
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Irons
Well-known member
I think it was 4Metals that had a post on reducing Silver Nitrate with Sodium Formate. It gives you Silver metal.
I saw that post too, but failed to comment on it earlier.
I saw that post too, but failed to comment on it earlier.
Here's 4metals' posts on the subject:
http://www.goldrefiningforum.com/phpBB3/viewtopic.php?f=50&t=1275&hilit=formate
He does no cementation on copper. The silver is dropped directly from the silver nitrate solution, after adjusting the pH on both the silver nitrate solution and the sodium formate solution.
http://www.goldrefiningforum.com/phpBB3/viewtopic.php?f=50&t=1275&hilit=formate
He does no cementation on copper. The silver is dropped directly from the silver nitrate solution, after adjusting the pH on both the silver nitrate solution and the sodium formate solution.
Irons
Well-known member
goldsilverpro said:
Looks like I better start collecting Ants come Spring.
Irons said:
No it wasn't 4Metals or any of the "regular suspects". I should've made a note of the particular post. Now it's adrift in the data-sea Noxx has created here.
Anyhow, I'm puzzled by the formic acid reduction thingy, as I mentioned before.
Irons
Well-known member
jsargent said:
Try This:
http://goldrefiningforum.com/phpBB3/viewtopic.php?f=50&t=1275#p39590
I had an unnamed member here tell me to go pinch ant butts once upon a time in relation to 4metals reduction method. It was the first I made the connection, but this solution is right up Irons alley. I like how he keeps it basic when possible and it never hurts to have an alternative to the chemical suppliers.
shadybear
Well-known member
So how many ant butts does it take to reduce 2 liters of silver nitrate
and does it matter what size the ant butt is? Would big butt ants work better?
and does it matter what size the ant butt is? Would big butt ants work better?
Irons
Well-known member
Palladium said:
More than I expected. :lol: :lol:
Ant's produce formic acid in their stingers.
Some birds actually irritate ants on purpose to get the ants to spray their feathers down with formic acid for protection from parasites.
Steve
Some birds actually irritate ants on purpose to get the ants to spray their feathers down with formic acid for protection from parasites.
Steve
Chuckle... no it was not 4Metals. It was AuBro. from this post (and quite an amazing post it was): http://goldrefiningforum.com/phpBB3/viewtopic.php?f=52&t=2259&p=19283&hilit=formic#p19283Oz said:
What puzzles me is this statement AuBro makes and it puzzles me because I've never heard anyone recommend reduction prior to cementation:
"7) Before any cementation, ALLWAYS, get rid of any Oxidizing agents (HNO3, HClO). they will redisolve your valuables and you will be confused and waste precious chemicals. A nice reducing agent is Formic Acid (HCOOH). Once placed in hot oxidizing solution (HNO3) forms Carbon monoxide that goes into the air; leaving no anions in solution. VERY CLEAN. Stop when the solution stops bubling. It is harder to get though and maybe more costly, but worth the investment. Check around. Another One is Urea, however the endpoint for neutralization is harder to see; stops fizzing. If you do not have any of these, evaporate twice until almost dryness. Rehydrate with HCL 2% - 5%."
So tell how ion exchange between copper and silver is supposed to happen if the oxidizing agent (nitric acid) is removed? Unless the solution can saturate with copper, or some metal higher in the electromotive series than silver, one will never recover all the silver. Does AuBro mean to say just add enough reducing agent to LESSEN, but not entirely remove the nitric, in order to reduce the saturation capacity of the solution, or what?
No it wasn't that post it was this one: http://goldrefiningforum.com/phpBB3/viewtopic.php?f=52&t=2259&p=19283&hilit=formic#p19283 (see item #7)
Though I must say the post by 4Metals on using formate INSTEAD of copper cementation may be superior still. Takes a long damn time to saturate with copper a silver nitrate solution containing 100 ounces of silver, especially when using scrap bus bars. Gets expensive too with copper being up in price.
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I don't have a problem with your comments about the price of copper, but I'm not sure you have it right with the point of saturation. There is no relationship between the percentage of copper in solution and the cementing of silver. There is an electron exchange that results in silver being cemented, and copper being dissolved. Take note that you can recover silver instantly with copper, from a solution of nothing but silver nitrate, with no dissolved copper present.jsargent said:
You can recover 100 ounces very quickly. Simply present a large surface area to the solution. The greater the area, the faster the cementation. Use more, or larger, pieces of copper.
Harold
This is the point with 4metals process, by removing the nitric you already have elemental silver and the copper cementation is not used.jsargent said:
I have not seen the thread you are referencing in a long time. I was trying to give credit where it was due as I thought you were referring to what 4metals had first posted here for precipitating silver from nitric.
In reading the post you are talking about it seems (at least to me) that formic acid was being suggested for the removal of oxidizing agents from AR prior to cementation on copper. It goes without saying that there would be no silver in solution with AR having formed a silver chloride precipitate if it was present.
If you wished to use formic acid for precipitating silver from a nitric solution I would follow 4metals direction as it makes little sense to start with formic then change to copper cementation part of the way through.
Hopefully you see where the confusion came from as no ill will was intended. At least we are all on the same page now.
Well maybe I'm not using the term "saturation" properly. In any case here is what I observe: Let's say we start with a couple gallons of pefectly clear siver nitrate containg 100 ounces of silver in solution. Obviosly the solution is acidic with free nitric acid. Immediately up placing copper bars in the solution, silver begins to cement out. The problem is that the resulting surface area on the silver curds as they fall away from the copper, far exceed the surface area of the copper bars so the silver rapidly re-dissolves. After many hours of this, enough of the free nitric is consumed by the copper to bring to solution to near saturation, i.e. no more copper will dissolve. However, if this point is reached prior to all the silver being cemented out, the reaction will stall and the color of the solution will be emerald green, indicating abundant silver still in solution, rather than the cobalt blue indicating a completed cementation reaction. At this point I always have to add a bit more nitric to complete the process by dissolving more copper to complete the ion exchange. Hence, my original question regarding AuBro's formic acid post.Harold_V said:
