Fig. 13.
§ 35. The "bottle" form of the bichromate or chromic acid battery (as illustrated at [Fig. 13]) is much employed where powerful currents of short duration are required. It consists of a globular bottle with a rather long wide neck, in which are placed two long narrow graphite plates, electrically connected to each other and to one of the binding screws on the top. Between these two plates is a sliding rod, carrying at its lower extremity the plate of zinc. This sliding rod can be lowered and raised, or retained in any position, by means of a set screw. The zinc is in metallic connection with the other binding screw. This battery (which, owing to the facility with which the zinc can be removed from the fluid, is extremely convenient and economical for short experiments) may be charged with either of the following fluids:—
First Recipe.
Bichromate Solution.
Bichromate of potash (finely powdered) 3 oz.
Boiling water 1 pint.
Stir with a glass rod, allow to cool, then add, in a fine stream, with constant stirring,
Strong sulphuric acid (oil of vitriol) 3 fluid oz.