Spectrophotometric determination of praseodymium, neodymium, and samarium

Praseodymium, neodymium, and samarium, in nitrate solutions, have been determined by measuring the transmittancies of the solutions with a doublemonochromator photoelectric spectrophotometer.Spectral transmittancy curves from 350 to 1,000 mil were obtained for lanthanum, cerium, praseodymium, neodymium, samarium, europium, and gadolinium.The absorption band found to be most suitable for the determination of praseodymium was at 446 mil; for neodymium, the bands at 521 and 798 mil; and for samarium, 402 mil.Lanthanum, cerium, and gadolinium show negligible absorption between 400 and 1,000 mil.Europium shows a sma)) absorption band at 396 mil.Transmittancy-concentration curves were obtained for the individual elements in concentrations ranging from 0.25 to 25 mg/m!.These curves show that for concentrations up to 10 mg/ml, solutions of neodymium follow Beer's law, while in concentrations greater than 10 mg/ml this law does not hold.Praseodymium and samarium solutions do not follow Beer's law under the conditions used.Approximately 1 mg of praseodymium per 6 ml can be detected.The sensitivity of the neodymium test depends on the band used; 1.5 mg can be detected by using the 521 mIL band and 0.5 mg by using the 798 mil band.The test for samarium is less sensitive than for the other two elements, 3 mg being the minimum detected.Mixtures of the three elements were analyzed and also mixtures of each of the three elements with lanthanum.The mixtures varied from one containing 5.0 mg of neodymium and 200 mg of lanthanum, to one consisting of 75 mg of samarium, 75 mg of praseodymium, and 50 mg of neodymium.A weight of mixed oxides corresponding to approximately 200 mg of rare earth elements was used for each analysis.The accuracy obtained was of the order of ± 3 mg.A method is given for correcting the slight interference of each element in a mixture, and a procedure is outlined for the analysis of a mixture of the cerium group of elements obtained during the course of a mineral analysis.