TAPPI T 613 2010 Edition, January 1, 2010
Analysis of caustic soda
This method describes a procedure for the analysis of caustic soda (sodium hydroxide). The following determinations comprise the usual complete analysis: alkalinity (total), carbonate, chloride, iron, and sulfate.
Most of the caustic soda used by the pulp and paper industry is a water solution of approximately 50% or 73% NaOH; it is also available in solid, flake, or ground (powder) form. Commercially, it is quoted on a 76% sodium oxide (Na2O) basis, approximately equivalent to 98% NaOH.