Analysis, Volumetric

( Chem.) A branch of chemical analysis in which the substance treated is subjected to characteristic reactions, for which solutions of known strength are employed. From the quantity of these that is required, the quantity of the substance sought can be determined by aid of the fixed laws of equivalence. These proce es usually require le time and le elaborate apparatus than the ordinary methods of analysis by weight, and as the results are equally if not more accurate, they are well adapted for technical purposes, as when the valuation of commercial products is sought. As an example we may mention the method salt. In the ordinary method of analysis, a known weight of the silver-containing substance is di olved in nitric acid. Then, by the addition of hydrochloric acid, an insoluble chloride of silver is formed and precipitated. This, after being separated by filtration, is washed, dried, fused, and carefully weighed. As the composition of silver chloride is well known, the amount of silver present in the precipitate can then be easily calculated. In V. A. , a solution of common salt, of known strength, is slowly added to the nitric acid silver solution until the precipitate ceases to form, when the proce is stopped, and the exact quantity of the salt solution added is ascertained. As it is known that 58.5 parts by weight of salt (sodium chloride), will convert 108 parts by weight of silver into silver chloride, it become easy to determine the weight of silver present in the precipitate. This operation can be completed in half an hour, while the former would occupy half a day; it is also more nearly accurate in result. In addition to analysis by precipitation, alkimetric and acidimetric methods are employed, and also analysis by oxidation or reduction, in which the same principle of employing a known quantity of acid or alkali, or of a reducing agent, is employed, and the result estimated as before.