How can one dissolve gold? Ever wondered! Everyone seems to be talking about gold these days. Over the past two to three years in these economically uncertain times, people have gone out buying gold in large quantities.
Some of us perhaps will have invested in gold coins or be lucky enough to have one. Some of us will have little bits of gold jewelry such as cufflinks but in fact, even if you have none of those but just own a computer, you know what look closely at the contacts.
Read: How do we interact with mineral resources?
Because on this old-style memory card you can see that the contacts are made of gold apart from the fact that it’s beautiful, that it’s attractive, and that it holds so much wealth.
It also has wonderful properties and its electrical conductivity is almost unparalleled in the periodic table and that’s the reason why the most reliable contacts are actually made with a thin coating of gold over the underlying wires.
One of the reasons why gold was seen as so special is actually its complete lack of reactivity. It doesn’t tarnish. It doesn’t alter with time but in fact, gold does react and I’d like to tell you two quick ways.
The first method to Dissolve Gold
We can take a little drop of mercury and see its effect on gold. On a tiny strip of gold leaf put a little bit of mercury. Now watch as the greedy mercury grabs the gold forming a solution called an amalgam.
If you poke it around you can actually see the gold disappear into the bulk of the mercury until at the end all we’re left with is a silvery drop. But there is a second way of dissolving gold and that is to use what was called Aqua Regia royal water and that’s what you get when you start to combine mineral acids.
The second method to Dissolve Gold
Aqua Regia method
Use three parts of spirits of salts as the alchemist called it and we’re going to use three parts of that to one part of nitric acid.
Three to one mixture is an extremely aggressive acid and the intriguing thing is that most metals will dissolve in nitric acid. Many will dissolve in hydrochloric acid.
Gold is untouched by either and the only acid that will actually dissolve it is this combination. So take a little gold leaf, pick it up and see if you can dissolve it.
In the acid, you can see a little bit of bubbling and that’s the gold beginning to react. What we’re doing is we’re actually making gold chloride salts, chloroauric salts and the gold is gradually dissolving and so now just a few minutes later you can see that the solution has now gone completely clear and our gold has been completely dissolved by our royal water. What we have here is a solution of gold.
Nitric acid can be successfully substituted with any kind of it salts. Any nitrate and hydrochloric acid will make almost the same thing as a prop aqua regia not exactly the same but almost the same. Well from a practical point of view it will be just less reactive and that’s it.
You can use any nitrate. It will work to dissolve your gold. But I don’t recommend using calcium nitrate. When it comes to calcium nitrate and if it gets mixed with sulfuric acid it will make something called calcium sulfate or in other words gypsum.
Gypsum is absolutely insoluble and also it’s quite a pain to filter it. Also, try to avoid ammonium nitrate. You can use magnesium nitrate. So just mix it with hydrochloric acid and if it will be not enough add a bit more nitrate and just wait till all of the nitrates dissolves.
At the first reaction, it will be exothermic and it will produce quite a lot of heat itself. Later you can see some bubbling. Also, you do not want to leave your aqua regia open. Most of the gas is produced well except for hydrogen are so really useful gases both chlorine and nitrogen dioxide.
Actually, the ones dissolving your gold or helping to dissolve your gold. And you cannot seal your aqua regia completely because sooner or later it will produce so much pressure, that it will simply explode. Whenever you see some bubbling just leave it like that. If the reaction stops and you can see there is quite a lot to dissolve.
First, it is recommended to add extra nitrate, and only after adding extra nitrate, you will apply some heat. What it will do? It will nicely neutralize chlorine and also nitrogen dioxide. So your workplace will be times less smelly.
So everything dissolved leaving just some dark grey-black sediment. Aqua regia itself changed its color from a tea color to a kind of green. This tells that aqua regia successfully decomposed because tea color is quite native to aqua regia.
Speaking about sediment so far we are not certain what it is. Could be some silver because silver is not dissolving in aqua regia. Also, it could be some absolute crap or it even could be some carbon.
Extracting gold from gold solution
We need sodium sulfide for this. Be careful when you handle the gold solution because gold solutions are very toxic. Add some sodium sulfide to it. You can see that the gold color solution turns into a colorless solution after a few minutes.
You can see the gold particles precipitate out. You can see the color changing. You must do this experiment by yourself. If you want to do this experiment you must do this experiment outdoor or in a fume hood because this reaction gives sulfur dioxide gas.
Sulfur dioxide is a toxic gas. Now we have to wait. After the reaction is mostly complete we can see all the gold precipitate out. We can collect the gold and do the rest.
So the black precipitate is our gold and now you can see the solution is like a blue color because we started with the reaction of 22 karat gold. Because of this copper, there are two-plus ions. So copper two-plus is the blue color.
So that’s why the solution is light blue. So you can now collect all gold powder and heat this gold powder and get a nice shiny gold bead. Before the heat, you can add some borax to this gold precipitate to melt down.
This gold is in low temperature. Now you can add this gold bead to water. You can that your final product is 24 karat gold. We started with 22 karat gold but finally with 24 karat gold.