Density gradients forming apparatus

Figure 38-3. A simple density gradient forming where D, = the density of the lighter liquid. = the apparatus, density of the heavier liquid. F, = the volume of the lighter (Courtesy - The Textile Institute, Manchester, England)...

Column apparatus can be very simple, since the entire pH-gradient between the electrode can be utilized. No special electrode vessels are necessary. Steps must be taken, however, to prevent gas bubbles from the electrodes from entering the separation compartment. A very simple type of apparatus has been described by Svensson (3) (see Figure 9), and a similar apparatus was used 65 years ago by Picton and Linder (55). They did not use a density gradient for stabilization purposes. The gas bubbles formed at the central electrode develop only inside the central tube, which protects the density gradient. Thus they do not enter the separation compartment. The bubbles from the top electrode are developed close to the upper surface, to which they rise, and do not cause any convection in the separation compartment. 

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