Complexometric determination of aluminium and scandium using fluorides as masking agent at low pH value

A complexometric method is suggested to determine Al and Sc by back titration of Bi(NO3)3 solution with xylenol orange indicator at low pH values. To increase selectivity fluoride additions were used which were masked by boron acid at the end titration point. EDTA was used as a complexing agent. Metals which create at low pH values stable complexes with EDTA undestroyed by fluoride, do not interfere with Al and Sc determination. Scandium is shown to be determined more selectively than aluminium