<prompt> The fluoride ion concentration in aqueous solution of acidulated phosphate fluoride solution is-1.322.231.232.32  <response>: An aqueous solution of acidulated phosphate fluoride is prepared by dissolving 20 grams of sodium fluoride in 1 liter of 0.1 M phosphoric acid and to this is added 50 hydrofluoric acid to adjust the pH at 3.0 and fluoride ion concentration at 1.23. It is also called as Brudevolds solution. 