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  • 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 we examined the chemical resistance of gold.

  • In this video we're going examine the chemical resistance of platinum.

  • Here I have a one troy ounce bar of platinum metal.

  • The first test will be in hydrochloric acid so I'm wrapping it in aluminum foil for comparison purposes.

  • Here is the concentrated hydrochloric acid.

  • I'm putting this round bottom flask over it to keep it from splashing out.

  • What's happening is the acid is reacting with the aluminum foil to form hydrogen gas and aluminum trichloride.

  • Since it's highly concentrated the aluminum trichloride hydrate is precipitating out as a powder.

  • I'm going to add some water to completely dissolve it.

  • And here is the platinum bar. Let me get it out of there.

  • The hydrochloric acid completely destroyed the aluminum but the platinum bar is perfectly fine.

  • Now for the sulfuric acid test.

  • I have here some sugar and I'm adding to it some concentrated sulfuric acid.

  • Let me toss in the platinum bar.

  • And now we wait.

  • What's happening is the sulfuric acid is removing water from the sugar and leaving behind carbon.

  • Now the platinum bar is embedded in this pillar of carbon so let me retrieve it.

  • And there it is.

  • Oh I think I scratched it when I jabbed it with my spatula. Oh well.

  • The sulfuric acid itself did no damage to the platinum.

  • Now for the nitric acid test.

  • For comparison I'm also going to toss in a piece of copper.

  • The nitric acid is reacting with the copper to produce copper nitrate and this brown nitrogen dioxide gas.

  • Okay looks like the reaction is done.

  • And here is platinum bar, completely immune to the nitric acid.

  • Now for the reaction with molten sodium hydroxide.

  • I'm putting these pellets on the surface and now I'm going to heat it with a torch.

  • The sodium hydroxide is melting and as I continue heating it... oh look, it's turning brown.

  • Either the sodium hydroxide is turning brown or the platinum is.

  • Let me let it cool and we'll remove the sodium hydroxide to be certain.

  • The sodium hydroxide is solidifying so we'll need to dissolve it in water.

  • Here we go.

  • Looks like the brown color is permanent.

  • Platinum can be tarnished by molten sodium hydroxide.

  • What happened was under molten alkali conditions platinum is oxidized by air.

  • So what we have here is a surface coating of platinum oxide.

  • Anyway there we have it, platinum can be damaged by molten sodium hydroxide.

  • For those interested, of course I'll be dissolving this in aqua regia in a later video.

  • Thanks for watching.

  • In this video we'll look at the chemical resistance of gold.

  • In this video we're going to dissolve platinum in a combination of nitric and hydrochloric acids, better known as aqua regia.

Warning: This experiment uses highly corrosive chemicals and produces toxic gases.

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