Colorimetric estimation of thorium with quinalizarin

Color Reaction between Thorium and Quercetin and Separation Scheme for Interfering Ions

“…Other reagents which have been utilized successfully are Alizarin Red S (28, 84), carminic acid (17), and p-arsonic acid (83). Several proposed reagents are Carmine Red (11), naphthazarin (27), quinalizarin (30), and oxalohydroxamic acid (9). Morin is reported to be extremely sensitive to thorium (12).…”

Spectrophotometric determination of thorium with molybdophosphoric acid

“…Other reagents which have been utilized successfully are alizarin red S (2), naphthazarin (3), quinalizarin (4), quercetin (5), carmine red (6), carminic acid (7), Erichrome Black T (S), and , -arsonic acid (9). The most sensitive chemical procedure currently available appears to be the spectrophotometric method using morin (10), which is capable of determining about 0.2 pg of thorium in a 50-ml volume using 5-cm cells.…”