Gravimetric determination of manganese with 8-hydroxy-quinoline

Abstract

Precipitates of manganese oxyquinolinate obtained from a mineral acid solution containing a slight excess of oxine by adding dilute ammonia, according to Berg’s second method, could be dried to constant weight at 150°C. and weighed. A slight superficial discoloration which may be observed in some cases is inappreciable even when dealing with small amounts of manganese. The composition of the dried precipitate corresponds to Mn(C₉H₆ON₂ and contains 16·03% manganese. Satisfactory results are obtained in a single precipitation provided a large excess of oxine is not added. A large excess of oxine with or without the addition of strong ammonia tends to yield higher results. Double precipitation does not improve the accuracy of the results in such cases. The presence of large amounts of ammonium or sodium chloride does not appreciably affect the accuracy of the results. Small amounts of manganese ranging from 0·3 to 4·0 mg. could be satisfactorily determined in presence of large amounts of sodium chloride and strong ammonia.