T 1475 (OTTO) Tetramethylammonium hydroxide 25% in water Cas 75-59-2 - used to produce tetramethyl-ammonium azide. T 1475 (OTTO) Tetramethylammonium hydroxide 25% in water Cas 75-59-2 - used as an anisotropic etchant of silicon, as a basic solvent in the development of acidic photoresist in photolithography process, as a surfactant in the synthesis of ferrofluid and as a polarographic reagent.