Sodium Sulfite Stoichiometric Dose Ratio

Calculates the mass of sodium sulfite required per unit mass of dissolved oxygen, from molar masses and the 2:1 stoichiometry. Gives 7.88 ppm sulfite per 1 ppm oxygen on a stoichiometric basis.

$$\text{Mass ratio}=\frac{2\times 126\text{g/mol}}{32\text{g/mol}}=\frac{252}{32}=7.88$$

Variables

Symbol	Meaning	Unit
126	Molar mass of sodium sulfite (Na2SO3)	g/mol
32	Molar mass of oxygen (O2)	g/mol
2	Moles of sulfite per mole of oxygen	mol/mol

Worked example

Stoichiometric requirement is 7.88 ppm sodium sulfite per 1 ppm dissolved oxygen. In practice, about 10 ppm sulfite is fed per 1 ppm oxygen to maintain a measurable boiler residual of 20 to 60 ppm.

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Part of The Blueprint of Water