The difference effect (Delta) behaviour of magnesium is studied in Na2SO4, NaBr, MgSO4 and MgBr2 solutions up to 2.0 M concentration using galvano-gasometry set up. Comparison of the hydrogen gas evolution rates obtained from galvano-gasometry method and from the atomic absorption spectrophotometer (AAS) shows a lower value in the former. A transition from positive difference effect to negative difference effect in sodium salt solutions and its absence in magnesium salt solutions are observed during the study. The current density at which the transition occurred is termed as transition current density denoted by the symbol i(tau). The relationship of i(tau) with the nature and concentration of the electrolytes are also discussed in this communication.