Hydrogen peroxide can be prepared by the action of dil. $H_{2}S{O}_4$ or $H_{3}P{O}_4$ on barium peroxide or by bubbling carbon dioxide through a thin paste of barium peroxide. On an industrial scale it can be prepared by hydrolysis of peroxodisulphuric acid obtained by electrolysis of 50% $H_{2}S{O}_4$ or an equimolar mixture of $H_{2}S{O}_4$ and ammonium sulphate. The strength of $H_2{O}_2$ solution can be expressed in a number ways namely normality molarity percentage strength and volume strength. Volume strength refers to the volume of $O_2$ produced at N.T.P by decomposition of 1mL of $H_2{O}_2$ solution $H_2{O}_2$ acts as an oxidising as well a reducing agent both in acidic and basic media (molar volume of any gas at S.T.P =22.4lit)