If it dries out it shrinks, and the organic content is consumed generating CO₂
K₂SO₄ - not the imperial droid
https://www.google.com/search?q=2+subscript+unicode
The free version works OK, and for 99p it can do something fancy, I’m not sure what though.
Subscripts especially for CO₂, has been irksome for me for ages.
If it dries out it shrinks, and the organic content is consumed generating CO₂