Mixed acid-base indicators Terms

The last of these methods has been applied particularly to chemical reaction vessels. It is covered in detail in Chapter 17. In most cases, however, the RTDs have not been correlated with impeller characteristics or other mixing parameters. Largely this also is true of most mixing investigations, but Figure 10.3 is an uncommon example of correlation of blend time in terms of Reynolds number for the popular pitched blade turbine impeller. As expected, the blend time levels off beyond a certain mixing intensity, in this case beyond Reynolds numbers of 30,000 or so. The acid-base indicator technique was used. Other details of the test work and the scatter of the data are not revealed in the published information. Another practical solution of the problem is typified by Table 10.1 which relates blend time to power input to... 

EMF measurements on the ZnQa-AQ (A = K, Rb or Cs) systems have yielded partial molar free energies, enthalpies and entropies, and the results have been interpreted in terms of an acid-base reaction. Tlie enthalpy of mixing consists of a contribution from the reaction to form the tetrahedral complex A2ZnCl4, and a contribution from the mixing of the products with remaining reactants to form a solution. The results indicate that as the polarizing power of the alkaU metal cation decreases, the reaction part of the enthalpy becomes more pronounced, reflecting the increased basicity of the alkali metal salt. 

In 1680, Robert Boyle noted that acids (1) dissolve many substances, (2) change the colors of some natural dyes (indicators), and (3) lose their characteristic properties when mixed with alkalis (bases). By 1814, J. Gay-Lussac concluded that acids neutralize bases and that the two classes of substances should be defined in terms of their reactions with each other. 

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