Warning: This experiment uses highly corrosive chemicals and produces toxic gases.
This should be performed with gloves in a fume hood.
Greetings fellow nerds.
In a previous video I dissolved platinum into aqua regia.
In this video I’ll be processing the crude platinum solution from that reaction into purified chloroplatinic acid.
First we need to concentrate the crude platinum solution.
You can do this by heated evaporation or by boiling.
But if you boil you should cover the beaker with an empty round bottom flask
to prevent splashing out of the valuable platinum solution.
Anyway, since we started with a 31.1g platinum bar, we concentrate the solution down to less than 100mL.
Once it’s down turn off the heating and let it cool back down to room temperature.
Okay back again.
Now we add an equal volume of hydrochloric acid and gently heat the mixture
while covered with an empty flask to prevent splash outs.
Do not add the acid while hot or it might boil over.
Any leftover nitric acid from the aqua regia will react with the hydrochloric acid to produce a combination of
nitrogen dioxide, nitrosyl chloride, chlorine and nitrogen monoxide.
Originally these were unwanted side reactions when dissolving platinum
but we’re now taking advantage of them to destroy residual nitric acid.
The brown gas forming shows nitric acid is still present. Keep boiling as long as you see it.
If the mixture gets below 100 mL then turn off heating and allow to cool.
Then top it up with another 100mL of concentrated hydrochloric acid.
Restart the heating and keep going.
When all the nitric acid is destroyed the vapor will be clear.
Looks like all the residual nitric acid is destroyed.
But I'm going to give it one more hydrochloric acid treatment just to make sure.
Okay  confirmed, the nitric acid is gone.
Now once again boil it or evaporate it to concentrate it but this time we go down to 50 mL.
Then turn off the heating and let it evaporate normally at room temperature.
We can’t heat it dry because it decomposes into insoluble platinum chlorides.
If it’s not drying at room temperature on air then you might need to use the desiccator bag I showed in a previous video.
Personally I'm using a professional vacuum desiccator.
Here we are with the dried chloroplatinic acid. Break it up and transfer it to vials.
And here we have nice chunks of the purified chloroplatinic acid.
As always, be sure to label your vials.
Now chloroplatinic acid has the extremely annoying property that it’s highly hygroscopic.
You can see the beaker and bits of chloroplatinic acid getting wetter and wetter as it absorbs water from the air.
In between uses I recommend storing the vials in a dessicator while they are slightly open to keep the contents dry.
Anyway that is purified lab grade chloroplatinic acid.
This is a useful precursor to other platinum compounds I’ll be showing in later videos.
Thanks for watching.
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In this video we’re going to dissolve platinum in a combination of nitric and hydrochloric acids, better known as aqua regia.
In this video we're going to examine the chemical resistance of platinum.
