AB 1-100

Aluminum compounds dissolved in water are treated with an organic complexing agent (gluconate or tartrate) and the pH is adjusted with NaOH to 11.5...12. The free alkali is now titrated and the solution is treated with potassium fluoride. After the reaction has been completed the released alkali, which is proportional to the aluminum content, is back-titrated with HCl.

Al(OH)₃ + KF → K₃AlF₆ + 3 OH^-