Ive got 10 ounces of sterling I am trying to dissolve. So far ive added almost 2 liters of 70% nitric acid solution and its been about 2 hours. It starts to fume a small amouont each time I add it, but quickly stops and the solution is green(which from reading another post, may mean theres no more free nitric). Did I get a bad batch of nitric?
Why is my silver not dissolving in the nitric acid?
- Thread starter pljohnson
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martyn111
Well-known member
Try diluting your nitric 50/50 with distilled water.
qst42know
Well-known member
Green says nickel to me are you certain this is sterling.
qst42know
Well-known member
pljohnson said:
Tested, how?
qst42know
Well-known member
It's very common to find silver plated nickel silver. It would be uncommon to find unmarked sterling silver items.
qst42know
Well-known member
Can you be more specific as to what this scrap is?
As a test take a small piece of this material and put it in AR. A high silver alloy will be immune and a high nickel alloy will be dissolved.
As a test take a small piece of this material and put it in AR. A high silver alloy will be immune and a high nickel alloy will be dissolved.
If you start with 70% nitric, dilute it 50/50 with distilled water, and heat it, it will dissolve sterling silver 100% of the time, without fail, without exception. Actually, it's not even necessary to heat it, although it does speed things up. If the metal does not dissolve, it is not sterling silver. And, like qst intimated, if it isn't marked sterling, it most likely isn't sterling.
The answer to your original question, "Why is my silver not dissolving in the nitric", is either because your sterling silver isn't really sterling silver or your nitric isn't really nitric.
The answer to your original question, "Why is my silver not dissolving in the nitric", is either because your sterling silver isn't really sterling silver or your nitric isn't really nitric.
philddreamer
Well-known member
Did you incinerate your material before running thru acid? It makes a difference.
Juan Manuel Arcos Frank
Well-known member
I agree with GSP...you have to heat the acid solution and silver must be in shot form or laminated because the process needs a hig superficial area to dissolve silver,I mean,if you dip in nitric acid a bar of sterling silver it will not dissolve fast.
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Regards.
Manuel
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Regards.
Manuel
Shot is small little BB's of metal made by melting the sterling and pouring it into cold water, pouring straight into water from a crucible makes cornflake shot, which is big and ugly with a lot of surface area, (a good thing) pouring it through a crucible with small holes drilled in it to assure a fine stream makes BB's. Both are good, make whatever is easier.
I have digested 500 ounce bars of sterling in 50% nitric and they digested completely, just slow because the surface area wasn't there, but I did it so as not to overload the scrubber with the red cloud.
Make sure you are using chloride free water! Take a few drops of silver nitrate and add it to the water you are using, if it forms any white cloud the water has chloride in it and it will stop the reaction, done finito, nada! If it is sterling, and it is nitric, and the water has no chlorides, the sterling will dissolve, and the acid will be a beautiful blue (from the copper).
I have digested 500 ounce bars of sterling in 50% nitric and they digested completely, just slow because the surface area wasn't there, but I did it so as not to overload the scrubber with the red cloud.
Make sure you are using chloride free water! Take a few drops of silver nitrate and add it to the water you are using, if it forms any white cloud the water has chloride in it and it will stop the reaction, done finito, nada! If it is sterling, and it is nitric, and the water has no chlorides, the sterling will dissolve, and the acid will be a beautiful blue (from the copper).
If I am reading this thread correctly pljohnson has been using 70% nitric and not diluting it. If he does have sterling under those conditions it will be slow to react. If he starts to add heat it will start to react and as the nitric concentration comes down it will become far more efficient. So efficient as to possibly become a runaway reaction (depending on the available surface area of his silver) since it is an exothermic process. It is a bad day having silver nitrate foaming out of your beaker onto who knows what.
With that caution out of the way, I have never needed a stronger nitric for silver than 70% doubled in volume with distilled water (what most here call 50/50 nitric). 4metals makes a good point on chlorides, some city waters may actually be high enough in it to cause a pacification layer of silver chloride that would bring the reaction to a near stop.
With that caution out of the way, I have never needed a stronger nitric for silver than 70% doubled in volume with distilled water (what most here call 50/50 nitric). 4metals makes a good point on chlorides, some city waters may actually be high enough in it to cause a pacification layer of silver chloride that would bring the reaction to a near stop.
pljohnson said:
No problem, I am glad to hear I could help. My greater concern was that if I was right about what you had and you were preparing to add heat to drive the reaction based on advice you had been given, that it would result in a runaway reaction spilling your acid and silver all over the place if you had not diluted your 70% nitric. In my haste to reply I actually did a rather poor job of explaining it in terms that could be beneficial to others with similar circumstances.
Many people assume that just because something is stronger or more concentrated it will do the job better or faster. That often does not hold true with chemistry. The simple explanation in this case is that plain old water “allows the room” in a nitric solution for a reaction to occur. Concentrated nitric is a far slower reaction than 50/50 nitric and it can surprise you unexpectedly if it becomes diluted at a given temperature as it consumes your nitric, then starts to heat up due to a more efficient reaction that greatly speeds things along even faster.
Frankly 50/50 nitric is not the most efficient way to digest sterling silver, it is however a good balance between expediency of time vs. cost of nitric. Typically if I have sterling that I wish to digest in nitric I do the math as to how much 50/50 nitric it will require before anything else. I then place the silver in an appropriately sized beaker and add the distilled water and one third of the nitric needed. Keep adding nitric when the reaction slows, then finish off with heat. You will find that added heat is not required in the beginning as the chemical reaction generates plenty on its own (exothermic).
There are a few good reasons to follow the above. It minimizes the risk of runaway reactions even if digesting shot or cemented silver that you need to remove platinum group metals from, and it economizes on nitric acid consumption. With the greater portion of water compared to nitric in your beginning solution it allows some of your red NO2 gas to be reabsorbed into solution (that extra water) to do additional work instead of being wasted as a gas and being a toxic byproduct that should be scrubbed. To be fair, there are many tradeoffs between time and cost in refining but taking the slow path at first is always the best route until you have gained hands on experience.
Just to be clear in case you or another think my advice is condescending in nature. I myself practice the multiple additions of nitric because I have more time than money for reagents at this moment. If the situation came up that time became of the essence, I would drive reactions hard and fast the same as you will if the need arises once you gain experience.
