My guess is what is being observed is that initially, the silver begins dissolving in the nitric, but the reaction begins to slow rapidly - silver is not very soluble in concentrated (say 70%) nitric acid. This is because the solution is already heavy with ions. The addition of distilled water gives the silver nitrate somewhere to dissolve after reaction with the acid (silver nitrate 219gm / 100ml solubility in H2O). So, the addition of distilled water would give the false appearance that it is making the reaction proceed, when really, it is allowing the silver to be more easily dissolved into solution. First of all apologies if i caused offence that was not my intention. Secondly if this comes a cross as condescending that is also not my intent. You are correct in that solids will stop dissolving in liquids when they reach a certain concentration. So if this was just a dissolving reaction the above would be true. ( this is called the saturation point of a liquid) Try dissolving table salt in water. Eventually it will stop dissolving. However the above is a chemical reaction. So the more concentrated the solution the quicker it would proceed (rate kinetics). If you look at the equation: Ag + 2HNO3 --> AgNO3 + NO2 + H2O For every four ions you lose (the 2HNO3 on the left of the reaction) you only gain 2 ions (AgNO3) so the actual concentration of ions decreases. This is in direct opposition to the implied part of the statement "This is because the solution is already heavy with ions". In this case the "dissolving" of the silver is not related to the concentration of ions in solution. I have made one assumption. I am assuming that they have added enough volume of acid to dissolve all the silver present. hope this helps. Nick
Many, many thanks Nick. Say I used predecimal shillings: 50% silver, 40% copper, 5% zinc, 5% nickel (I think). What becomes of the copper etc?
^^This is my experience. If you don't add enough water, and keep digesting silver, the silver nitrate solution becomes saturated, and silver nitrate crystallises out of solution. Easy fixed by just adding more water to redissolve the crystals. The rest of your explanation makes perfect sense. Thanks.
copper will dissolve into the nitric acid as well. You might come across the technique of adding a copper pipe to 'cement' out the silver.
No problems, I have done it many times. Make sure you try and exhaust the acid. Then, as Jislizard said, place copper pipe into the solution to drop out the silver (pure). 2 rules I have learned! Avoid dissolving anything with Tin in Nitric - it forms metastannic acid - an insoluble grey paste and a real biatch to deal with. Also, avoid using tap water (chlorinated) - silver chloride forms as a white insoluble powder, and is also a pain in the ass.
Just be very careful anyone doing this. Looking at some of the by product gases and vapours, through some chemical selection respiratory guides and you start seeing things like air fed breathing apparatus, self contained breathing apparatus etc... This is some serious safety equipment and NOT the stuff you will buy at Bunnings or your local hardware store. It is very specialised and expensive. So please make sure you know all the precautions before doing it. Even if someone else does it, does not mean it is safe. Personally as mentioned above for $25 silver this is just not worth the risk of dying, yes dying...
Very true. World War One mustard gas works in a very similar fashion. That's how dangerous this can be. As an aside I have two degrees in chemistry and medicinal chemistry. I have a casual disregard for lots if dangerous chemicals (lead, barium ect). The ones I seriously respect are picric acid, hydrofluric acid and conc nitric acid. If you have kids or pets you like don't use them.
I am sure that if handled correctly it is fine, however too many will not. As example ask yourself these questions - - Does someone know what I am doing and what to do in an emergency. Scenario - your wife comes looking for you in the shed, but you are on the floor she runs in only to be effected by the gas as well. Now two of you are in some trouble... - Are the relevant contact numbers at the ready etc... - Do you have a means of communication where you are working with it - What is the correct safe handling procedure - Is there a reagent I need to be aware of (explosions) - In case of a burn what is the procedures - Do I have all the correct PPE, are you using safety glasses, goggles or a face shield. You should be wearing two of them handling ANY dangerous liquids. - If I spill something do I have the correct spill pads for cleanup and disposal. and so on These are just some off the top of my head, if you have not even thought of these perhaps you should. NB ^^ you have handled a lot of chemicals and know the does and don'ts that is different from a novice not handling chemicals before, and to start with something nasty straight of the bat with little to no experience or processes in place. Here is a link for those who may not be aware what some of these can do, this is hydrofluoric acid - http://www.monash.edu.au/ohs/topics/hazard-alerts/hydrofluoric-acid-fatality.html Just to add here is a link to safety company in Vic that has some very good products, you cannot get onto Alcoa without carrying a spray of diphoterene - http://www.amare.com.au/search/12//Chemical-Burn-Treatment
Silver Production from Silver Nitrate using a Copper Pipe [youtube]http://www.youtube.com/watch?v=7tKTEZgHB1M[/youtube]
Cheers Greg I had not seen that one and will definitely follow it up. Dont know about anyone else but I find this exciting and am looking forward to doing this. But not until all information including safety matters is in hand. This is what silver is really about to me.
There you go! http://www.ebay.com.au/itm/Fume-Cupboard-PE-/151062823105 It does need an exhaust motor on it and it doesn't look like it has a filter on it so I wouldn't want to be downwind of the exhaust. If I was going to do a lot of this sort of thing I would probably get one, if I was just going to have a go to see what it was like I would probably just do it outside and try to hold my breath.
