Caustic poison erodes mucosa because -

caustic soda is sodium hydroxide * In concentrated form, alkali acts as corrosive and in dilute form they act as irritant strong alkalis absorbs water from tissues and precipitates protein * Strong alkali produces liquefaction necrosis and causes saponification of fats and dissolves proteins thus causing deep penetration in the tissue resulting in extensive tissue destruction REF;THE SYNOPSIS OF FORENSIC MEDICINE:KS NARAYANA REDDY;28th EDITION;PAGE NO302