Almost immediately, you'll see a bubbling reaction begin and the liquid start to change colour from clear to a very pretty blue shade. This blue colour is due to the copper in the coins reacting with the nitric acid to produce copper nitrate.
Also, brown vapours of nitrogen dioxide will also form.
WARNING Nitrogen dioxide is a NASTY, NASTY, NASTY gas and under no circumstances should you breathe it in. As mentioned earlier, do all this refining in the open air and you'll be perfectly ok.
To speed up the reaction, we can place the glass tube into a bath of boiling hot water. As the bath water cools, replace with fresh, boiling water.
Now, we sit back and let the reaction continue until both coins have been completely dissolved leaving behind just a brilliant blue liquid.
When the coins are completely dissolved, we need to dilute this blue liquid a bit so add an equal volume of water.
Next, we need to remove any sediment by pouring this blue liquid through a filter into the 2nd of our glass jars.
Here's how to create a suitable filter using one of the coffee filters.
1. Use a round lid to mark out a circular pattern on the filter.
2. Cut out the circular shape.
3. Fold the circular filter in half ... then fold in half again.
4. Carefully open up the filter and you'll find it should fit easily into the plastic funnel.
Place the funnel and filter into the opening of the 2nd (empty) glass jar and carefully pour the blue liquid into the funnel, allowing it to drip through.
By the way, you ARE wearing your plastic gloves, aren't you ? If you splash the blue liquid onto skin you'll get a harmless black discoloration that will take about 4 days to wear off. So wear your gloves !! That black discoloration is caused by silver in the blue liquid reacting to light and darkening ... the basis of how photographic film works :-)
Should have taken my own advice
Ok, we want to get every last bit of silver so once the liquid has finished running through the filter paper, use the plastic water spray bottle and spray the inside surface of the filter to ensure that all the blue solution has passed through the filter.
So here we have a jar containing the filtered blue liquid with all our silver dissolved in it. But how do we get the liquid to release the dissolved silver back as a solid material ? Well, it just so happens that when a piece of solid copper is placed into the blue liquid, copper atoms in the solid copper and silver atoms in the blue liquid immediately start to exchange places. The solid copper begins to slowly dissolve and a grey, foam-like material begins to appear and fall to the bottom of the glass tube.
This grey material is pure silver ! Wooohoooo !
A small copper cylinder would do the job nicely but for our purposes, I'm simply going to use an old electrical power cable like the one that plugs into a computer or a kettle, etc and strip out one of the copper wires. Then I'll wind the copper wire around a pencil to create a rough helix shape.
Take this piece of copper wire and drop it into the glass jar containing the filtered blue liquid.
Within seconds, you should see a grey, foam-like material begin to coat the wire. When it gets heavy enough, it will detach from the wire and fall to the bottom of the jar and more will start to form. Otherwise a slight shake of the jar should be sufficient to dislodge it.
If the copper wires dissolves completely, then add another similar piece of copper wire and repeat until there is no further grey material visible on the wire. This means that virtually all the silver has been removed from the blue solution and should now be at the bottom of the glass jar in the form of a grey sediment.
Now we're going to "wash" the grey material to remove all traces of remaining blue liquid.
We'll prepare another filter as we did before and fit it into the plastic funnel. Now the funnel is placed into the original glass jar that we dissolved the coins in and very slowly and carefully, the blue liquid and grey sediment is poured into the funnel. We want to let the filter catch every last bit of grey sediment.
When done, the water spray bottle will be used to spray the grey sediment in the filter until the water coming out of the bottom of the funnel is clear.
All of the liquid in the glass jar can now be tipped into a bucket, diluted with lots of water and then can be safely discarded by pouring down the sink drain ... no damage will occur.
Continued next post ...
edit on 18/2/12 by tauristercus because: (no reason given)