View source for 106.3.2.56 TM-56, Determination of Sodium Metasilicate (Na2SiO3)

This method determines the percent of anhydrous sodium metasilicate (Na<sub>2</sub>SiO<sub>3</sub>) in automotive antifreeze by Atomic Absorption Spectrophotometry.

==106.3.2.56.1 Reagents and Apparatus==

1) An Atomic Absorption Spectrophotometer.

2) Potassium Chloride (KCl), Reagent Grade.

3) Ethylene Glycol, Reagent Grade.

4) Silicon Standard Solution, 1000 ppm. This solution can be purchased from a number of sources.

==106.3.2.56.2 Preparation of Standard Solutions==

0,000 ppm Potassium Stock Solution: Weigh 19.068 g of dried, reagent grade KCl into a
1000-mL volumetric flask, dissolve, and dilute to volume with distilled water.

152% Na<sub>2</sub>SiO<sub>3</sub> Standard: Pipette a 20-mL aliquot of 10,000 ppm K stock solution and a 7-mL aliquot of 1000 ppm Si standard solution into a 200-mL volumetric flask. Add 20.00 g of reagent grade ethylene glycol and dilute to volume with distilled water.

0.109% Na<sub>2</sub>SiO<sub>3</sub> Standard: Pipette a 20-mL aliquot of 10,000 ppm K stock solution and a 5-mL aliquot of 1000 ppm Si standard solution into a 200-mL volumetric flask. Add 20.00 g of reagent grade ethylene glycol and dilute to volume with distilled water.

Blank Solution: Pipette a 10-mL aliquot of 10,000 ppm K stock solution into a 100-mL volumetric flask. Add 10.00 g of reagent grade ethylene glycol and dilute to volume with distilled water.

==106.3.2.56.3 Procedure==
Weigh, to the nearest 0.1 mg, 10 ± 0.05 g antifreeze into a 100-mL volumetric flask. Pipette a 10-mL aliquot of 10,000 ppm K stock solution into the volumetric flask and dilute to volume with distilled water.

Calibrate the instrument with the blank solution, the 0.109% Na<sub>2</sub>SiO<sub>3</sub> solution and the 0.152%
Na<sub>2</sub>SiO<sub>3</sub> solution, then determine the concentration of the sample solution.

==106.3.2.56.4 Calculation and Report==
The method of calculating the % sodium metasilicate will vary according to the make and model of instrument used.

Report the results to the nearest 0.01% Na<sub>2</sub>SiO<sub>3</sub> as follows:

:% Sodium Metasilicate (Na<sub>2</sub>SiO<sub>3</sub>), anhydrous


[[Category:106.3.2 Material Inspection Test Methods]]