CONSECUTIVE CHELATOMETRIC MICRO-DETERMINATION OF SCANDIUM AND THE SUM OF OTHER RARE EARTHS

Less than 1 mg of scandium can be titrated in a porcelain crucible with disodium salt of ethylenediamine tetraacetic acid(EDTA),using xylenol orange as indicator.For titrations of 1—400 μg of scandium oxide,the relative errors lie within the range of +0.8 to-2.1%.This indicator is good for the consecutive chelatometric titrations of microgram-amounts of scandium and milligram-quantities(0.1—20mg)of the other rare earths.The scandium titration is carried out at pH 1.8—2.2,and the light lanthanons to- gether with yttrium,at pH 5.0—5.5 after adding hexamethylene tetramine.Light lan- thanons up to 25 mg do not interfere with the scandium titration,while larger amounts of light lanthanons and yttrium can be masked with sulphosalicylic acid.Interference of ceric cerium can be minimized by reducing it to the cerous state.The relative errors for titrating consecutively microgram-quantities of scandium and millgram-quantities of light lanthanons are±1% and 0—1% respectively.The effect of diverse ions is given. The authors wish to thank Dr.R.P(?)ibil of Czechoslovak Academy of Sciences for the gift of xylenol orange.