Haring-Blum cathode

The Haring-Blum cathode is divided into two equal plane areas, distant f 1 and fj from a common anode, and a quantity called the primary current density ratio P is defined as... 

On this scale, zero represents the case when M = P, and electrolyte resistance is the main factor. Throwing power can be worse, down to a limit T = - 100% when A/ = oo, i.e. no deposit at all on the far cathode. Conversely, when M < P, T is positive. Were M to reach 1-0 despite the difference in position, 7" = -F 100%. At one time +100% was regarded as an unrealisable limit, but conditions have been found for which T = -f150% in a Haring-Blum cell. 

Haring-Blum cell — A rectangular cell with two cathodes at the small ends with an anode placed between them (see Fig. 1). The two cathodes are connected electrically. Usually the ratio, L, of the two anode-cathode distances is five. Thus a high current density (hcd) and a low current density (led) edge results. The Haring-Blum cell is used to determine the macro - throwing power, TP, of an electrolyte, according to the relation TP = (L - M) / (L + M - 2) where M is the ratio of the deposited masses. 

The throwing power of a bath is a measure of its ability to produce electroplated coatings of uniform thickness on samples having complex geometries. A quantitative measure of this property can be defined in terms of the so-called Haring and Blum cell, which is used to determine it. In this cell, two cathodes are positioned at unequal distances from two sides of an anode, as shown in Fig. 24M. The throwing power (T.P.) is defined as ... 

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