Rapid determination of aluminum and fluorine in the presence of each other

Abstract

Aluminum and fluorine form a stable complexion, and it has been considered that the quantitative determination of either of these elements from their solution is interfered by the other.
However, a rapid determination of the two elements is possible by the use of the following procedure:
A sample solution containing 515 mg aluminum and 0400 mg of fluoride ions is prepared.
It is made up to about 150 ml with water; 10 ml of 5% oxine solution of acetic acid acidity is added, and then sodium hydroxide is added to above pH 12. Acetic acid is added to pH 10, and the mixture is heated at 70°C. The precipitate is filtered off, washed, and dried for determination of aluminum.
The filtrate is made up to a definite volume, a portion equivalent to about 10mg fluorine is adjusted to pH 59, and the excess of oxine is removed by extraction with chloroform. The solution is then made up to 150 ml, and adjusted to pH 3, and the fluorine is determined by the usual method of titration with thorium nitrate.