![]() ![]() The reagent of exactly known concentration is refered to as standard reagent. This involves measuring volume of solution of known concentration that is needed to react completely with the sample. Titrimetric methods include powerful group of quantitative procedures that are based on measuring the amount of reagent consumed by the analyte. The volume or mass of the reagent needed to react completely with a fixed quantity of the analyte is obtained from which the amount of analyte is determined. Titration is based on a reaction between the analyte (unknown sample) and the regent of known concentration and reaction stoichiometry. TITRIMETRIC MTHODS Titrimetric methods are widely used in chemistry to determine oxidants, reductants, acids, bases, metal ions, etc. Let's examine these options for two very simple examples (Figure A.1): These are in a fashion all representations of the same thing – a desire to express the character of a chemical compound in a manner that will be understandable to others. Molecules can be described in terms of a structural drawing, a written name or a formula. We shall try and provide just a basic and introductory nomenclature here, even neglecting some more advanced aspects of naming for the sake of brevity and clarity. Collectively, these place a great deal of demand on the nomenclature system, to the point where it has become both sophisticated and difficult to use. For coordination chemistry, we need to deal with a number of aspects – the ligands (of which there may be more than one type), the central metal (or metals, in some cases), metal oxidation state(s), ligand distributions around the metal(s) and counter-ions (if the compound is ionic). The object of the nomenclature adopted is to provide information on the full stoichiometric formula and shape of a compound in a systematic manner. This body produces 'dictionaries' for chemical nomenclature that serve in much the same way as a conventional dictionary, thesaurus or grammar rule book, and which are updated regularly. One advantage is that it is a universal language, governed by rules set in place by the International Union of Pure and Applied Chemists (IUPAC). In a sense, chemical nomenclature is as much a language as is Greek or Mandarin, albeit a restricted one with a very specific purpose it has an organized structure, 'rules of grammar', conventions, and undergoes continuous evolution. In describing chemical substances, we are dealing with a need for effective communication using an appropriate language. Constant development in the field has demanded evolution of nomenclature, and the international rules were revised or supplemented in 1959, 1970, 1977, 1990 and again early in the twentyfirst century like all languages, chemical language continues to evolve. Although an international 'language' for organic molecules commenced from a meeting in 1892, it was some time later that a systematic international inorganic nomenclature developed, and it was as late as 1940 that a full systematic nomenclature was assembled. His system of leading with the names of ligands followed by the metal name, as well as also employing structural 'locators', is still with us today. ![]() ![]() In large part, our current approach in coordination chemistry derived from nomenclature concepts introduced by Werner to represent the range of new complexes that he and contemporaries were developing, providing both composition and structural information. Since nomenclature evolved along with chemistry, it was far from systematic even up to the beginning of the twentieth century. This was eventually addressed in the early days of 'modern' chemistry in the late eighteenth century, and modern nomenclature evolved from that early work. From very early times, alchemists gave names to substances, although these names gave little if any indication of the actual composition and or structure, which is the aim of a true nomenclature. ![]()
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