الفهرس 
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Abstract
The free convection mass transfer behaviour of fixed beds of randomly packed Raschig rings (aspect ratio= I) has been investigated experimentaly using an electrochemical technique involving the measurement of the limiting current for the cathodic deposition of copper from acidified copper sulfate solutions Variables studied were physical properties of the solutions, ring diameter and bed height. The data were correlated for the range 10.6xl06< Sc.Gr<20.9x 107 by the equation
Sh= O.15(Sc.Grf32
The exponent 0.32 reveals a turbulent flow mechanism, bed height and ring diameter were found to have little effect on the mass transfer coefficient; thus confirming the turbulent nature of the flow.
Mass transfer rates were also measured for the cathodic deposition of copper from copper sulfate at a gas evolving fixed bed electrode built of randomly packed Raschig rings or cylinders (aspect ratio=l). Variables studied were bed height and rIng or cylinder diameter. The data for the range 1703<Sc<2070; 1.68x I O•IJ<Fr.Re< 1.1 x IO•K were correlated for rings by the equation:
J= 1.4(Re.Fr)’(JI62
The data for fixed bed of cylinders under the same conditions fit the equation:
J= 1.58(Re.Fr)-0166
Bed height was found to have little effect on the mass transfer coet1icicnt.