This SOPs covers a method for determination of aluminum in alumino silicate refractory materials.

Aluminum (also iron and titanium when present) is complexed quantitatively with EDTA by boiling with an excess of the reagent. The excess EDTA is back titrated with standard zinc acetate solution at pH 5.3 using xylenol orange indicator. The aluminum EDTA complex (also titanium EDTA complex, if present) on boiling with sodium fluoride liberates EDTA which when titrated with standard zinc acetate solution gives the amount of aluminum and titanium present in the solution. Due correction for titania is also carried out.

• Burette – 50 ml
• Measuring Cylinder – 50ml
• Pipette – 10 ml

• EDTA solution 0.025 M – Dissolve 9.31 g of EDTA (disodium salt) in 1 litre of water. 
• Methyl Orange indicator- 0.05 percent (m/v) in ethanol. 
• Dilute ammonia solution – 1:2 (v/v). 
• Buffer solution (pH 5.3]
• Xylenol orange indicator solution 0.7 % (m/v) – Dissolve 0.1 g of xylenol orange indicator in 100 ml of water containing 2-3 drops of dilute hydrochloric acid (1: 1). 
• Standard zinc acetate solution (0.025 M) – Dissolve 5.50 g of zinc acetate in 1 000 ml of water containing 25 ml of buffer solution (pH 5.3). Standardize against standard aluminum solution.
• Standard aluminum solution (0.025 M) -Take an aluminum foil and wash it with absolute alcohol and dry in a desiccator. Weigh O.674 5 g of aluminum foil into a beaker containing 25 ml of water and 25 ml of concentrated hydrochloric acid. Heat the solution to dissolve the metal. Cool and dilute the solution to 1000 ml in a volumetric flask (1 ml – 0.001275 g of Al2O3). 
• Sodium fluoride – Solid. 
• Dilute hydrochloric acid – 1: 3 (v/v)

• Transfer 25 ml of main solution (Determination of silica – IS: 12107 (Part 2)-I 987) to a 250 conical flask.
•  Add 35 ml of EDTA solution and 2-3 drops of methyl orange indicator solution. 
• Add dilute ammonia solution dropwise to just yellow color. Add 15 ml of buffer solution and boil for 5 minutes. Cool to room temperature.
• Add 5-6 drops of xylenol orange indicator and titrate the solution with standard zinc acetate solution to just pink color. 
• Add 1 g of sodium fluoride to the solution followed by 2-3 drops of dilute hydrochloric acid. Boil the solution again for 5 minutes. Cool to room temperature. 
• Add 5 ml of buffer solution and titrate the released EDTA with standard zinc acetate solution using 5-6 drops of xylenol orange indicator to pink end Point. The second titrate (V ml) corresponds to the amount of titanium and aluminum.

Reference Standard: IS 12107: 1987 part – 3