Iron and Sulfuric Acid Conversion Method Taking Too Long

[Buildeddie97]

Hello All,

I have a large batch of silver chloride that I have been trying to convert. I don't have an exact weight but it fills up about 400 ml of a 1000 ml beaker. I also had 98% sulfuric acid.

I did plenty of reading and small scale tests that say "fill up the beaker to above the silver chloride level and then add about 1/10th that volume of sulfuric acid with excess iron" so this is exactly what I did. I then mixed it very well and would do this several times a day. After about 1 week, there was almost no change. I split up the mixture and kept one the standard method and then added more sulfuric acid to the test beaker. After another week, there was still no change. I've even used heat for extended periods of time.

Is there something that I am doing wrong or does this process just take a long time with large batches?

Thank you for any and all help!
Edward

 

[butcher]

Not being able to see whats going on it is hard to help.
Assuming the white wet silver chloride still damp and fluffy (not dried or black silver crust coated salt of silver), You should notice the conversion taking place as the white silver chloride comes into contact with the clean oil and rust free iron metal, the white silver chloride turning darker where it contacts the iron.

Heat and stirring can help the chloride come into better contact with the iron. you may also increase surface area of the iron, try using more Horse shoe nails or a clean cast iron skillet...

 

[Lino1406]

If there is no water present, sulfuric acid over 85% will not corrode iron,what is a part of the process

 

[Buildeddie97]

Butcher,

How long should this process reasonably take? I have been trying for weeks now. Have you ever worked with this large of a sample?

Lino, I added a lot of water before pouring in the sulfuric acid to make a pretty dilute mixture. Is there something else I'm missing?

 

[butcher]

It should not take long, as stated before as the silver chloride comes into contact with the clean iron, so that an electron is taken by the silver ion from an atom of iron, in order to reduce the silver salt to a gray heavier metal powder, and the iron atom upon losing its electron share it bond with the chloride ions, where the iron goes into solution as a green solution of dissolve ions of the iron chloride solution, you should see the white fluffy cheese looking silver, get grayish and heavier, less likely to stay fluffy floating around in solution.

Take a sample of fresh silver chloride in a test tube with a nail and try observing it.
How do you know if it reacted? or what form the silver is in?
if you stir a solution with silver chloride in it the white silver chloride is fluffy and light and will swirl around for a long time, if you stir a solution of silver metal powders they are heavy normal more gray towards blackish or violet, and the silver will settle in solution rather quickly...
Will a sample of the powders dissolve in nitric?
Silver metal will, silver chloride is insoluble.
Does it dissolve in ammonia?

What was the source of this silver? Maybe it is not iron you see floating, often silver can be plated, maybe with a metal that will not react to your acids...

 

[Buildeddie97]

Butcher,

I had a sample with some pure iron chunk of metal and it still didn't convert! I am very confused as to why it's not working with fresh sulfuric acid. It is creating a silver foam at the top of the beaker while still being the powder-y silver chloride at the bottom.

I will try the nitric acid and see if any dissolves. Worst comes to worst, it all dissolves and then I can just re-add salt to precipitate the silver chloride out again.

I am getting these silver samples from work so you are right that there is likely contamination from other metals. I just figured that them being in a nitric acid silver strip tank and washing them with HCl would get rid of pretty much all contaminants. The reason I think it is iron though is because I added the iron shavings early on when I ran tried the sulfuric acid conversion and they are still reacting to a magnet when I bring it close. but even after several days in the sulfuric acid and several days in the HCl, the iron is still there. I don't know honestly. I am confused and stressed about this. I really appreciate all the thought and responses you are putting in to help me out though!