331. A weighing of technical sodium hydroxide weighing 0.3251 g was dissolved in a volumetric flask with a capacity of 100 ml. For titration of 25 cm3 solution with phenolphthalein, 18.40 cm3 of 0.1 M HCl was used, and with methyl orange - 18.80 cm3 of the same acid. Calculate the mass fraction (wt %) of sodium hydroxide in the sample.

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