Sulfite Standard Solution preparation

Sulfite Standard Solution preparation: 

Sulfite Standard Solution (80 ppm SO2):  
Dissolve 3.150 g of anhydrous sodium sulfite in freshly prepared distilled water  and dilute to 100.0 mL with the same solvent. Dilute 0.5 mL to 100.0 mL with freshly  prepared distilled water.


Sulfite Standard Solution (1.5 ppm SO2):  
Dissolve sodium metabisulfite equivalent to 0.152 g of Na2S2O5 in water and  dilute to 100.0 mL with the same solvent. Dilute 5.0 mL of this solution to 100.0 mL  with water. To 3.0 mL of the resulting solution, add 4.0 mL of 0.1 M sodium  hydroxide and dilute to 100.0 mL with water.