Why does pure dry benzoic acid does not affect a litmus paper

Answer 1

https://www.jiskha.com/questions/1795757/Explain-why-pure-dry-benzoic-acid-does-not-affect-a-litmus-paper

Answer 2

Litmus paper is an indicator for the presence of an acidic solution (blue litmus => red) or alkaline solution (red litmus => blue). To understand this it is important to note that for a substance to become an acid or base two conditions must apply; that is, (1) the substance of interest must have water as a solvent which (2) effects ionization of the substance to yield hydronium ions (H₃O⁺ = H⁺) for an acidic solution or hydroxide ions (OHˉ) for an alkaline solution. Since benzoic acid in solid form is not in water, it will not ionize to deliver H⁺ ions into solution and litmus will be unable to detect H⁺ ions and change color.