I do not know the composition of gerbil urine

[bunsen_h]

But on drying, gerbil pee leaves a tough white residue, poorly soluble in water and difficult to remove from a plastic surface without damage to the plastic.  However, it is readily soluble in concentrated hydrochloric acid, with evolution of gas.  I suspect it's giving off CO2, but I don't have the resources to try to confirm.  It would probably

Comments

[resonant]

I have access to a lab, but no gerbils to test.