The sodium salt of 2-(2-hydroxy-3 3 6-disulfo-1- naphthylazo)-benzenearsonic acid, hereinafter referred to as thorin, has been extensively employed as a reagent for the spectrophotometric determination of thorium in recent years. No studies of the nature of the reaction between thorin and thorium have been reported. In this work, an examination of some properties of the complexes involved has been initiated.
Byrd, Carol H. and Banks, Charles V., "Spectrophotometric determination of thorium with the trisodium salt of 2-(2-hydroxy-3,6-disulfo-1-naphthylazo)-benzenearsonic acid and some properties of complexes involved" (1953). Ames Laboratory ISC Technical Reports. 62.