Watching a video of someone performing the Etard reaction, using CrO2Cl2 (chromyl chloride, a volatile, moisture-sensitive, fuming liquid, that looks somewhat like Br2, and is a powerful oxidizing agent, quite easily produced by mixing potassium or sodium dichromate, with excess salt, table salt, NaCl, that is, and then adding concentrated sulfuric acid, 98% will do it nicely, and distilling at a little over 117 'C which is the boiling point of chromyl chloride)
Useful, although a somewhat dangerous reagent, both for its being a powerful, usually aggressive oxidizer, a volatile liquid and being incompatible with many solvents, chloroform, carbon tetrachloride or methylene chloride being the go-to solvents for it, but its capable of selectively oxidizing an alcohol to an aldehyde. In the vid, the hobby chemist guy doing it is making benzaldehyde from benzyl alcohol. The latter being easily bought, cheaply, or OTC but needing distillation from some floor and tile cleaners, and benzaldehyde itself is used in synthetic almond essence. Smells lovely. I admit, I've bought it generally when needed, personally, the benzaldehyde that is, rather than either distilling synthetic almond essence or using the Etard, made some once though and just a little bit of the pure compound managed to 'stink' (actually it smells lovely) the entire room up like the marzipan equivalent f a cruise missile coming through the window, and hung around for days, making the lab smell like a sweet shop or bakery with an overwhelming sweet hum of marzipan/bitter almonds.
https://www.youtube.com/watch?v=rYKoj247rhg
