1. Formaldehyde (CHOH) is a gas.
2. Formalin 40 or 100% formalin is 37% (w/w) formaldehyde or
40% (w/v) formaldehyde.
3. Paraformaldehyde is a polymerized formaldehyde.
4. Methanol or some form of stabilizer is used in formalin to prevent
5. When methanol is not desirable for fixing, formaldehyde solution
is made directly from paraformaldehyde by heating the solution, thus
the paraformaldehyde fixing solution.