The mixture should be made in a glazed earthern vessel, and allowed to cool before using.
Second Recipe.
Chromic Acid Solution.
Chromic acid (chromic trioxide) 3 oz.
Water 1 pint.
Stir together till dissolved, then add gradually, with stirring,
Sulphuric acid 3 oz.
This also must not be used till cold.
In either case the bottle must not be more than three parts filled with the exciting fluid, to allow plenty of room for the zinc to be drawn right out of the liquid when not in use.
§ 36. The effects given by the above battery, though very powerful, are too transient to be of any service in continuous bell work. The following modification, known as the "Fuller" cell, is, however, useful where powerful currents are required, and, when carefully set up, may be made to do good service for five or six months at a stretch. The "Fuller" cell consists in an outer glass or glazed earthern vessel, in which stands a porous pot. In the porous pot is placed a large block of amalgamated zinc, that is cast around a stout copper rod, which carries the binding screw. This rod must be carefully protected from the action of the fluid, by being cased in an indiarubber tube. The amalgamation of the zinc must be kept up by putting a small quantity of mercury in the porous cell. The porous cells must be paraffined to within about half an inch of the bottom, to prevent too rapid diffusion of the liquids,