Sodium hydrogen carbonate stock

HPLC-grade formic acid (1 mL) sodium dihydrogen phosphate (12g.L ) sodium hydrogen carbonate (5 g) sodium vanillate stock solution (50 mg mL )... 

Acids and bases in Table 10-3 can be purchased in forms pure enough to be primary standards. NaOH and KOH are not primary standards because the reagent-grade materials contain carbonate (from reaction with atmospheric CO2) and adsorbed water. Solutions of NaOH and KOH must be standardized against a primary standard. Potassium hydrogen phthalate is convenient for this purpose. Solutions of NaOH for titrations are prepared by diluting a stock solution of 50 wt% aqueous NaOH. Sodium carbonate is relatively insoluble in this stock solution and settles to the bottom. 

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