Oxidation
It is oxidation because two O's 1 x 1 d 2 i's 1 n and 1 a
salt is not because it gets u dehydrated
If you’re referring to he red stuff- the liquids can be ethanol, toluene, kerosene, or isoamyl acetate. They’re transparent so they’re made more visible with red dye. (So I’d guess the answer is ethanol)
I found this in the Wikipedia article ‘Alcohol thermometer’