Answer to Question #126745 in Physical Chemistry for Eddy

Question

How does gravity affects Daniell cell?

Answer 1

Early 20th-century engraving of a gravity cell. Note the distinctive crowfoot shape of the zinc anode.

This variant, called a gravity cell, consists of a glass jar in which a copper cathode sat on the bottom and a zinc anode is suspended beneath the rim in the zinc sulfate layer. Copper sulfate crystals are scattered around the cathode and the jar then filled with distilled water. As the current is drawn, a layer of zinc sulfate solution forms at the top around the anode. This top layer is kept separate from the bottom copper sulfate layer by its lower density and by the polarity of the cell. A disadvantage of the gravity cell is that a current has to be continually drawn to keep the two solutions from mixing by diffusion, so it is unsuitable for intermittent use. In addition, it was vulnerable to loss of integrity if too much electric current is drawn, which also causes the layers to mix.