Volumetric methods kinds

NBS s involvment in SRM s for gas transmission studies arose out of activities within ASTM Committees D-20 (Plastics) and F-2 (Flexible Barrier Materials) that were aimed at standardizing a new instrumental method employing a coulometric oxygen detector for the measurement of oxygen gas transmission rates in materials used for various kinds of packaging (4 ). A subsequent reevaluation of the precision data for the classical manometric and volumetric methods (5) for gas transmission measurements showed that there are serious problems with the reproducibility and repeatability these methods. The use of SRM 1470 to verify the calibration is currently being written into ASTM standards D-3985 and D-1434. 

Among them, volumetric methods are presumably the most widely used for water analysis. They are titrimetric techniques which involve a chemical reaction between a precise concentration of a reagent or titrant and an accurately known volume of sample. The most common types of reactions as used within this method are acid-base neutralization, oxidation-reduction, precipitation, and complexation. The use of an indicator which identifies the equivalence point is required to develop this kind of method. The modem laboratories usually employ automated endpoint titrators, which largely improve the efficiency and reliability of the determination. Moreover, spectrophotometric, potentiometric, or amperometric methods to determine the endpoint of the reaction can... 

The overall association constant is =K, +K,K.+K,K.K. Most methods for studying ion association (such as conductivity or potentiometry, see below) provide values only for or K, but some methods (Section 1.12 and volumetric data according to Hemmes [25]) are able to distinguish between the three kinds of ion pairs. 

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