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1949
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Γ Ή Κ Ε Ε hundred registered for the second annual Summer Sym• posium of the Division of Analytical and Micro Chemistry on organic reagents, held last mouth at Wesleyan University. Many favorable comments on local meeting arrangements were expressed, and Professor Burford and his staff deserve the highest praise. S. E. Q. Ashley, the symposium chairman, is also to be congratu lated on organizing a splendid program. The meeting brought to focus the importance of organic reagents in analysis, and Pro fessor Feigl's review paper, "The Role of Organic Reagents in the Chemistry of Specific, Selective, and Sensitive Reactions," was timely and highlighted the meeting in that it placed emphasis on the fundamental structural properties which are responsible for the analytical adequacy of organic compounds with respect to selectivity, solubility, and color. In his discussion of the signifi cance of the chemistry of specific and selective reactions, the fol lowing topics were covered: atomic groupings in organic reagents, new complex compounds formed by organic reagents, real and false equilibrium by formation of metal-organic compounds, masking of reagents and innercomplex salts, and adsorption com pounds and lakes.
w h e n it's accuracy and control that counts
It is planned to publish the symposium papers in ANALYTICAL CHEMISTRY in November. Another paper of general interest by I. M. Kolthoff, "Amperometric Titrations with Organic Rea gents" (which the author does not now plan to submit for publica tion), stressed the advantages of such titrations as follows : The stoichiometry of the reaction during the titration and at the end point is found without collecting, washing, and drying the precipitate. Coprecipitation of other constituents during the titration can be established in a direct way The effect of factors which affect the solubility, such as p H , change of solvent, and presence of complex formers, is found easiiyFractional precipitations can be studied easily. If fractionable precipitation is possible, the successive titra tions of two metals or more can be carried out. The usual advantages of amperometric titrations, such as rapid performance, even at high dilutions, satisfactory accuracy, and graphical location of the end point pertain. Typical examples illustrate the above points. In the titration of cobalt with a-nitrose-,8-naphthol in acetate buffer the precipi tate contains 4 molecules of reagent per atom of cobalt, but in ammoniacal medium there are 3 molecules of reagent per atom of cobalt in the precipitate. Copper and palladium react with 2 molecules of reagent. The use of cupferron has been investigated in the titration of copper and iron. Both can be titrated in a citrate buffer. Al though ferric cupferronate is much less soluble than the copper compound, a quantitative fractional precipitation was not found possible. In 0.1 Ν hydrochloric acid iron can be titrated in the presence of the same amount of copper, but larger amounts inter fere. On the other hand, copper can be titrated in the presence of large amounts of iron when much potassium bifluoride is added. When a reagent does not portray satisfactory polarographic waves, it can be polarographically tagged. For example, the re duction wave of phenylarsonic acid is not suitable for ampero metric titrations. Introduction of a nitro group makes the com pound easily reducible. Results obtained with nitrophenylarsonic and tetraphenyl arsonium chloride as reagents were re ported. A DISPLAY by publishers of approximately 125 books on organic reagents and analytical chemistry, together with an exhibit of selected organic reagents by the Eastman Kodak Company and the G. Frederick Smith Chemical Company, attracted many visi tors. Professor Feigl's book, "Chemistry of Specific, Selective, and Sensitive Reactions," translated by Ralph E. Oesper, has just been announced by the Academic Press and, because it deals with principles and fundamentals of this subject, wall be found ex tremely useful in research in this important field.
A ssociatc Editor
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