68) Which is the smallest potential, which can produce electrolytic deposition when applied to an electrolytic cell.

69) The oxidation number of Aluminium in Aluminium metal is

70) Heavy metals are converted into its _____ for precipitation and separation in effluent treatment

71) Electro-forming of _____ is possible

72) Which is the elastic like force existing in surface of a body, especially a liquid tending to minimize the area of the surface.