Argon is an interesting one. A comparison between chemically synthesised nitrogen and ‘pure’ nitrogen extracted from the air (with the oxygen, carbon dioxide an

Argon is an interesting one. A comparison between chemically synthesised nitrogen and ‘pure’ nitrogen extracted from the air (with the oxygen, carbon dioxide and water removed) revealed a discrepancy: https://en.wikipedia.org/wiki/Argon#History https://en.wikipedia.org/wiki/Argon#History https://www.youtube.com/watch?v=loqudG71uBM https://www.youtube.com/watch?v=loqudG71uBM (Chemistorian, noble gases)