Tris(2-hydroxyethyl)methylammonium Hydroxide (CAS 33667-48-0), a quaternary ammonium hydroxide with formula C?H??NO?, is supplied as a 45-50% aqueous solution (molecular weight 181.23 g/mol). It acts as a strong, non-volatile base, used in organic synthesis (e.g., deprotonation) and electronics (photoresist processing). It requires sealed, cool storage to avoid CO? absorption; handle with protective gear due to high alkalinity, ensuring safety and performance in applications.