Neutron activation methods for the determination of the rare earths in minerals

11 1.311 Growth of Activity on irradiation 14 1.312 Decay of radioactivity 15 1.313 Determination of required constituent 16 1.3131Practical steps in analysis 18 1 ,12 Errors in Neutron Activation Analysis 20 1.321 Interfering nuclear reactions in lanthanides 23 1.33 Nuclear Properties of the Rare Earths 25 1.34 Survey of Published Methods 28 1.4 OBJECT OF PRESENT WORK 39 2 MEPERIMENTAL 42 -135 2.1 OUTLINE PLAN OF .7.7ESTIGATION 42 2.2 COUNTING EQUIPMENT 44 2.21 Solid Geiger-7qUller Counter 44 -vi 2.22 Gamma-Ray Scintillation Spectrometer 2.221 Apparatus 2.222 The scintillation process 2.223 Calibration of spectrometer 2.3 IRRADIATION OF MATERIALS 2.31 Ampouling of Samples 2.32 Choice of Irradiation Time 2.33 Self-shielding 2.331 Dilution of samples 2.332 Sodium from magnesia diluent 2.4 RADIOCHEMICAL PURIFICATION OF LANTHANUM AND YT:RIUM 2.41 Removal of Non-Rare-Earths 2.411 Sodium 2.412 Niobium 2.413 Phosphorous 2.414 Isolation of the rare earth group 2.42 Removal of Interfering Rare Earths 2.421 Separation of lanthanum and yttrium 2.422 Separation of praseodymium from yttrium 2.423 Separation of europium from yttrium 2.A231 Separation after reduction to Eu2+ -, ,1-Separation of holmium from yttrium ri 5 2.425 Procedure evolved for purifying La and Y 2.5 COUNTING TECHNIQUES 2.51 For Lanthanum 2.511 Sample-mounting 2.512 Stability of counter 2.513 Gamma scintillatipn spectra, 2.514 Contribution of14-Pr and 1°°Ho to lanthanum count 2.515 Spectra and decay curves of La separated from samples 2.52 For Yttrium 2.521 Sample--moue: in_ 2,522 Absorber cuo2veo -vii 2.523 Contribution of 152u and 166 Ho to Yttrium counting 2.524 Choice of optimum absorber thicknesscounti)4 time 2.525 Absorber and decay curves of J separated from samples 2.6 DETERMINATION OF CHEMICAL YIELD 2.61 Dry Hydrated Oxalates -Gravimetric 2.62 Ignited Oxides -Gravimetric 2.63 Oxalate -Permanganate Titration 2.64 Choice of Method 2.65 Effect of Co-precipitation of Nd with Yttrium 2.7 RECOMMENDED PROCEDURE 2.71 Health Precautions and Handling 2.72 Preparation and Standardisation of Reagents 2.73 Stepwise Procedure for Mineral Analysis 2.74 Modifications for Lanthanum-rich Minerals 2.741 In determination of lanthanum 12-2.742In determination of yttrium 2.75 Determination of Lanthanum without Fractionation 2.8 RESULTS OF MINERAL ANALYSIS 2.81 Table of Results 2.82 Estimate of P:7ecsion viii 3.