Hull cell

Testing and Control. Analysis and testing are required whenever a new plating solution is made up, and thereafter at periodic intervals. The analyses are relatively simple and require Httie equipment (78—80). Trace metal contaminants can be analy2ed using spot tests, colorimetricaHy, and with atomic absorption spectrophotometry (see Trace and residue analysis). Additives, chemical balance, impurity effects, and many other variables are tested with small plating cells, such as the Hull cell developed in 1937 (81,82). 

Current densities cited are average based on racked work, not Hull cell derived. 

W. Nohse, The Hull Cell, Robert Draper Ltd., Teddington, UK, 1966. 

Fig. 12.11 (a) Haring-Blum cell for throwing index measurement, in elevation and (b) Hull cell... 

The Hull cell cathode has a continuous variation of current density along its length, and there are equations which give the primary current density at any point not too near the end. If the local thickness is measured at two points for which P is known, Tcan be calculated. The real current distribution is a function of cathode and anode polarisation as well as of the resistance of the electrolyte. The metal distribution ratio will be... 

Throwing indices measured in a Hull cell differ from those in a Haring-Blum cell because of the differences in geometry. In a Hull cell several pairs of points can be found which have the same primary current ratio, but for which M and hence T are found to vary because of polarisation changes. 

Hull cell PHYS CHEM An electrodeposition cell that operates within a simultaneous range of known current densities. hoi, sel humectant chem A substance which absorbs or retains moisture examples are glycerol, propylene glycol, and sorbitol used in preparing confectioneries and dried fruit. hyu mek-tont ... 

Figure 12.1. Schematic of a Hull cell. (From Electrodeposition by J. W. Dini 1993 Noyes Publications, with permission.)...

Explain the basis for the operation of the Hull cell in other words, why it is expected that different points on a slanted cathode will be electroplated to different degrees. 

Hubble telescope Hudson-Bertrand rules Huffn puff HUFT theory Hull cell... 

Hull cell — The Hull cell is a trapezoidal cell (see Fig. 1) and is used for screening purposes of electrolytes. Due to the asymmetric shape the current varies over a wide range from the high current density (hed) to the low current density (led) edge. Thus the effect of the current density can be checked by visual inspection of the cathode after the plating process. A typical cell volume is 250 ml. A useful formula for the estimation of the local current density is i/im = -2.33 log(z) - 0.08, where im is the average current density and z the normalized distance from the hed edge. 

Current density distributions in electrochemical systems are governed by Laplace equation (Newman, 1991) with linear/nonlinear boundary condition at the boundaries (electrodes). Consider a Hull cell (see Fig. 6.13) in which a metal is deposited at the cathode (Subramanian and White, 1999). 

Consider current-potential distribution in a curvilinear Hull cell (Subramanian and White, 1999 Chapman, 1997 ). The governing equations and boundary conditions are ... 

The effect of current density on the structure of electrodeposits has been investigated in a special trapezoidal cell with a purposely nonuniform current distribution known as the Hull cell... 

FIGURE 26.24 The classical Hull cell for electroplating. All dimensions are in mm. Figure from [94] (copyright Elsevier 1994). 

Sugar Sbm Cell Wall Sb Cotyledon Cell Wall Sb Hull Cell Wall Combined Cotyledon And Hull... 

Aspinall, G.O. K. Hunt I.M. Morrison. Polysaccharides of soy-beans. Part II. Fractionation of hull cell-wall polysaccharides and the structure ofxylan./. Chem. Soc. 1966, 1945-1949. 

The Hull-cell (fig. 3.19) is one of the standard cells used in conventional plating industry to control the process parameters. As can be seen on the figure, the current density along the cathode varies in a wide range, from zero to infinity for a primary distribution, such that with one experiment the influence of the current density on the process can be investigated. 

Fig, 3.195 Hull-cell geometry and primary distribution along the cathode. 

Fig. 3.20 Current distributions in a Hull-cell three current distributions are represented all having the same total current. The formula (3.21) holds only for small Wagner numbers.

In section 3.5.1 we discussed the current distribution in a Hull-cell. This cell has an obtuse and a sharp angle and is therefore an interesting sample problem to check the electrode shape change algorithm. 

A very simple method to rotate an electrode is the rotation of an electrode rod or of an electrode cylinder. The calculation of the thickness of the diffusion layer is complicated but, in a first approximation, is proportional to an exponential dependence on rotation speed. An application of this method is the cell developed by Landolt for testing plating electrolytes. The standard equipment for such tests is the Hull cell (Figure 5.26). ... 

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