The application of combined ion cschange enrichment and c1.c. arc spectrochemical methods for determining trace clemcnts which are not detectable by direct excitation in rocks, soils and meteorites has been discussed by EDGE et aZ.1, BROOKS et aZ.2 and AHRENS et aZ.3*4. Anion exchange enrichment has been used for estimating Cd, Zn, Sn, Bi and Tl (observations have also been maclc on Nb, MO, In, A6 and the platinum metals)znfi.fl. Cation eschange techniques 3.7eR have been applied to tin, molybdenum, caesium and some rare earths and to a few elements detectable by direct d.c. arc excitation cg. scandium, gallium and rubidium. EDGE et al.1 have briefly outlined some of these investigations and AHKENS et al. 3 have described in detail the estimation of caesium in chondritic meteorites and basic rocks.
In the present paper investigations are described on the combined use of cation exchange enrichment and spectrochemical analysis for determining SC, Y, Nd, Ce and La in common silicate rocks (granites and diabascs). Although combined cation exchange-spectrochemical analysis procedures have been employed for estimating traces of rare earths in zirconium metal" and uranium compounds'0 and trace amounts of yttrium in bioto@cal material+', no workers appear to have employed this technique for estimating rare earths in silicate rocks.
Afifiaratrrs and reagents
EXPERIMENTAL
Standard spectrographic equipment was used and is described below together with the excitation conditions: Spectrogaph: Hilger E49z large quartz and glass. External optics: Hilger Eg58 lens focusscd on slit; step sector (2 : I ratio). Slit length: II cm. Slit width: 0.001