A SYSTEMATIC SEPARATION OF THE ANIONS OF GROUP I. ANIONS WHOSE SILVER SALTS ARE INSOLUBLE IN NITRIC ACID.¹

Abstract

having one duplicate, to the condition where calcium is ready for precipitation as oxalate. Summary.A more rapid and accurate method is recommended for the determination of calcium in the ash of agricultural products. It consists essentially in removing the phosphorus as ammonium phosphomolybdate from an acid solution of the ash, and precipitation of calcium from the filtrate as calcium oxalate, either directly or after the removal of the excess of molybdenum as sulfide. Since no advantage was found in removing the molybdenum, it is recommended that this step be omitted.A comparison of this method with the so-called basic acetate method in common use brings out the following points in its favor:I. It yields more accurate and concordant results than the basic acetate method.2 . No attention need be given to the maintenance of exact neutrality of the solution.3. The volume of the filtrate resulting from the precipitation of phosphorus can be kept reasonably small, so that no evaporation is necessary. 4. The time required for the determination is greatly shortened. 5. Phosphorus and calcium may be determined in the same aliquot. AMES, IOWA.The customary methods for the examination and separation of the acids depend mainly upon various group reactions, followed by specific tests for one or the other anion, combined with a process of elimination based upon the results of the analysis for the cations. For a limited number of anions special methods of separation have been worked out in detail, as for instance for certain of the acids containing sulfur. The literature on the separation of the halogens C1, Br, I, is quite voluminous and in this particular case a choice of various satisfactory methods of separation is possible. On the whole these methods are, however, limited in scope and very little work has been done upon systematic methods for the separation of the anions.2 1 Portions of this work were submitted by Mr. H. A. Winkelmapn in partial fulfilment of the requirements for the degree of Master of Science in Chemistry in the Graduate School of the University of Illinois, June, 1915. 2 The lack of such a systematic procedure is shown particularly by the errors and confusion resulting from the customary method of attack in the hands of students

A importância da Química Analítica Qualitativa nos cursos de Química das instituições de ensino superior brasileiras

“…Através de consulta ao Chemical Abstracts, verificou-se que grande parte dos trabalhos publicados sobre análises qualitativas até cerca da metade do século XX compreendiam, principalmente, estudos e aplicações de novos reagentes (geralmente orgânicos), novos testes para detecção de cátions e ânions usando técnicas microanalíticas , e vários estudos sobre métodos de separação de íons em uma análise sistemática [31][32][33][34][35][36][37][38][39][40][41][42][43][44][45][46][47][48][49][50] . A partir dos anos 60, as publicações sobre Química Analítica Qualitativa tiveram seu foco voltado para as atividades de ensino .…”