字幕列表 影片播放 列印英文字幕 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.