Zur Röntgen-Fluoreszenz-Spektralanalyse von Rubidium, Strontium, Barium und Blei in Kaolinen und Tonen

Abstract

An x-ray fluorescence spectrographic method is described for the determination of rubidium, strontium, barium and lead in kaolins and clays. The method is most usefull within a concentration range of 50–2000 p.p.m. Rb, Sr, Ba or Pb in the sample.

Dried powder samples of kaolins resp. clays are compressed in a suitably shaped die and its x-ray radiations are compared with those of the same kaolins or clays to which small amounts of Rb, Sr, Ba or Pb had been added. A homogenous distribution of small amounts of these elements in kaolins and clays is obtained by precipitation of Pb, Ba and Sr as sulfate and Rb as Rb[B(C₅H₆)₄] in a concentrated clay resp. kaolin suspension. The prepared suspensions are filtered (by membran-filters) and dried before compressing and x-ray measuring.

The instrumental conditions were: Siemens x-ray spectrograph “Kristalloflex IV” fitted with a lithium fluoride analysing crystall, molybdenum-target x-ray tube (type AG Mo 61), 50 kV 30 m.amp. for measuring of the Sr Kα-, Rb Kα-, Pb L/gB-lines and 60 kV 36 m.amp. for measuring of the Ba Kα-line.

The standard deviations were: ± 3 p.p.m. Rb for samples containing 25– 150 p.p.m. of Rb ± 6 p.p.m. Sr for samples containing 200– 400 p.p.m. of Sr ± 60 p.p.m. Ba for samples containing 1000–2000 p.p.m. of Ba ± 9 p.p.m. Pb for samples containing 250– 800 p.p.m. of Pb