Processing factors affecting functionality impurities

Most solutions used in the electrodeposition of metals and alloys contain one or more inorganic or organic additives that have a specific function in the deposition process. These additives (and impurities) affect the deposition and crystal-building processes as adsorbates (substances that are adsorbed) at the surface of the cathode. Adsorption and the factors that determine the adsorbate-surface interaction are discussed in detail in Volume 1 and Volume 2. 

The two azeotropic separation methods considered in Sections 5.1 and 5.2 required the addition of a third component to alter the vapor-liquid equilibrium. Another factor that sometime affects the phase equilibrium is pressure. If the composition of a binary azeotrope is a strong function of pressure, a two-column process can be used to achieve separation without adding a third component, which is desirable because small levels of impurity of this third component in the product streams are unavoidable. The two columns operate at different pressures, so the azeotropic compositions are different. 

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