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The behaviour of resorcinol succinein as an adsorption indicator in mixed halide solutions has been described. The applicability of two more dyes, dibromo. and tetrabromo- resorcinol succinein as adsorption indicators has been investigated. They have been found to be very suitable indicators for the titration of bromide, iodide and thiocyanate ions.

A new adsorption indicator, phenyl-\(\alpha\)-naphthylamine-azobenzene \(p\)-sulphonic acid has been suggested for argentometric titrations. It differs from all the classical adsorption indicators in having both acidic as well as basic character which makes it applicable both in the titrations of halide ions against silver ions as well as in the reverse titrations of snivel ions against halide ions in which acidic and basic dyes respectively used to be employed separately The adsorbability of the indicator, both by the positively as well as negatively charged silver halide bodies, endows it with a sharp colour change at the end-point, a ready reversibility and a large range of applicability in the argentometrie titrations

In a comparative study of the behaviour of resorcinol aconitein and tricarballylein as adsorption indicators in argentometric titations, it has been observed that whereas the latter Is a very suitable indicator for the purpose, the former does not develop any distinct colour on being adsorbed on the silver halide bodies. The observed difference has been explained in a simple manner and casually confirms the structure assigned to the aconitein by the previous workers. As a result of the investiga­tion, a very sensitive indicator for the titration of halide and thiocyanate ions against silver ions has been described.

A comparative study has been made between the applicability of dyes obtained from succinic and derived succinic acids and the corresponding dyes from maleic acids as adsorption indicators in argen­tometric titrations. It has been shown that whereas succinic acid derivatives resorcinol succinein and itaconein —serve as very useful indicators, the corresponding dyes from maleic acid do not have any applicability. The behaviour has been explained on the existing theories of colour and of adsorption indicators. As a result of the investigation, a new adsorption indicator, resorcinol itaconein, has been described.

A NOTE ON THE EFFECT OF SURFACE ACTIVE AGENTS ON ACIDALKALI INDICATORS