Determination of trace amounts of thorium and lanthanides by successive titrations using Semi-xylenol Orange with spectrophotometric end-point indication
Abstract
The precision and accuracy attainable in successive titrations of Th4+ and either La3+, Nd3+ or Gd3+ with a 0.001 M solution of disodium ethylenediaminetetraacetate using Semi-xylenol Orange (SXO) as a metallochromic indicator were studied. Thorium(IV) was titrated at pH 2, the pH was adjusted to 5.5–5.9 by adding hexamethylenetetramine buffer and La3+(or Nd3+ or Gd3+) was then titrated. A comparison of the indicators SXO and Xylenol Orange for successive titrations of Th4+ and either La3+, Nd3+ or Gd3+ was carried out.