1. For troughs, for general purposes, medical galvanism, etc.: Nitric acid 1 fluid oz., sulphuric acid 1 1/2 fluid oz. water 4 pints.

2. Dr. Faraday. Oil of vitriol 2 fluid oz., nitric acid 1 fluid oz. water 5 pints. It should be tried by dipping into it a piece of sheet zinc. A continuous succession of small bubbles should be produced.

3. For Mr. Smee's Battery. One measure of sulphuric acid to 7 of water. The intensity of its action is increased by the addition of a few drops of nitric acid, but this tends to destroy the plates. In electro-metallurgy the water should only contain a sixteenth of sulphuric acid.

4. For Mr. Grove's Battery. For the outer vessel, 1 pint of sulphuric acid to 7 of water: for the inner, concentrated nitric acid.

5. For Daniell's Battery. For the porous tube containing the zinc, 1 part of sulphuric acid with 10 of water. For the outer cylinder, a saturated solution of sulphate of copper, with a tenth part of sulphuric acid.

6. Nitro-sulphuric acid, for Dr. T. Wright's Batteries. Nitric acid 1 part, sulphuric acid 5 parts. The zinc plate is immersed in a solution of chloride of ammonium or of salt, the platinized zinc in the above acid. The platinizing requires to he repeated every time the plate is washed.