Quinhydrone

Chemical properties

a dark green crystalline powder which is a complex formed by benzoquinone and hydroquinone.

Quinhydrone is a general reagent used in potentiometric titrations. It can also be used as a π-acceptor in the formation of charge-transfer complex of analytes for spectrophotometric analysis.

The Uses of Quinhydrone

In pH determinations (quinhydrone electrode).

The Uses of Quinhydrone

Quinhydrone is a hydrogen bonded 1:1 charge transfer complex of hydroquinone and p-benzo-quinone having semiconducting properties.
Quinhydrone is addition compound of one mol hydroquinone and one mol Benzoquinone.
Quinhydrone electrode is a type of redox electrode which can be used to measure the hydrogen ion concentration (pH) of a solution in a chemical experiment.
Quinhydrone/methanol treatment for the measurement of carrier lifetime in crystalline silicon substrates has been reported. Surface passivation of silicon substrates by quinhydrone/ethanol treatment has been investigated.

The Uses of Quinhydrone

Used to measure the hydrogen ion concentration (pH) of a solution in a chemical experiment. It provides an alternative to the commonly used glass electrode in a pH meter.

Definition

ChEBI: Quinhydrone is an addition compound. It contains a 1,4-benzoquinone and a hydroquinone.

Definition

The so-called quinhydrone electrode, containing equivalent amounts of p-benzoquinone and hydroquinone, is used to determine hydrogen ion concentrations of unknown solutions. Hydroquinone is used principally as a photographic developing agent. The main advantages of the quinhydrone electrode are low internal resistance, rapid response, high accuracy, simplicity, free of errors due to the presence of nonreducing gases, and free of salt errors. Major limitations are that it contaminates the solution, cannot be used to monitor a flowing solution, the solution must be free of strong oxidizing and reducing agents, and it is limited to a pH range of 1 to 9. In alkaline solution, the weakly acidic H2Q is neutralized and is subject to oxidation by air and dissolved oxygen. The main application of the quinhydrone electrode is in nonaqueous solvents where reproducible results are obtained in a variety of solvents. The tetra-chloro derivative (chloranil electrode) is even more useful.

General Description

Quinhydrone/methanol treatment for the measurement of carrier lifetime in crystalline silicon substrates has been reported. Surface passivation of silicon substrates by quinhydrone/ethanol treatment has been investigated.

Hazard

Toxic by ingestion.

Purification Methods

Crystallise quinhydrone from H2O at 65o , then dry it in vacuo.[Beilstein 7 H 617, 7 IV 2069.]