REPORT
pound in the mixture may be called for. The amount present may be in the p.p.m. range or less, or it may be nearly 100 per cent. Extensive separation work by chemical or other means may have to be carried out to remove interfering constitu ents before identifications and measurements. One compound may have to be transformed into another for separation, identification, or measurement. Usually more than one parameter must be measured to ensure correct identification; some times complete proof of structure of a compound is necessary. Many such measurements can be stand ardized, and, where this is possi ble, are carried out by nonprofes sional workers under the supervi sion of experienced chemists. Analysis of samples, however, is only a part of the analytical chem ist's work in research. He has an other very important role. A major amount of his effort is devoted to diagnosis of problems, determining analytical needs, making decisions on how best to get the desired infor mation, evaluating and integrating the information with that of other chemists, working toward the com mon goal of creating or developing a new product or process, etc. To get the answers, he used x-ray, nmr, and mass spectroscopy; absorption spectrophotometry ; colorimetric, volumetric, gravimetric, and complexometric methods; all the tech niques of chromatography; thermochemical, electrochemical, radio chemical, semimicro and micro methods; and many others. The problems may be concerned with the misbehavior of a catalyst in a reaction, the search for and identifi cation of some impurity suspected of causing difficulty in a process, a kinetic study of a chemical reac tion, or measurement of a physical constant of a compound which may involve extensive purification or even synthesis. During the writing of this paragraph, within a single hour, the author received requests for (1) critical characterization of seven different chemical compounds thought (or hoped) to be pure; (2) a quick practical method for deter mining fractional p.p.m., possibly p.p.b., of an exotic chemical in water; and (3) analysis of a raw material for the chemical form of a
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