The gas liberated on heating a mixture of two salts with NaOH, give a reddish brown precipitate with an alkaline solution of K2Hgl4. The aqueous solution of the mixture on treatment with BaCl2 gives a white precipitate which is sparingly soluble in concentrated HCl. On heating the mixture with K2Cr2O7 and concentrated H2SO4, red vapour (A) are produced. The aqueous solution of the mixture gives a deep blue ppt. (B) with Potassium ferricyanide solution. Identify the radicals.