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Physical & Chemical properties

Melting point / freezing point

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Description of key information

Decomposition: 282 - 375 °C

Key value for chemical safety assessment

Additional information

Acid Red 131:1 is a multiconstituent substance composed by the acidic and the sodium salt forms of the same structure (70.9 % and 13 % of the substance respectively). EPI Suite v4.10 has been used in order to compare the two structures. The two results, derived from estimation of melting point by means of MPBPVP v1.43, are identical (349.84 °C both for the salt and for the acidic form) due to the great similarity between the two molecules.

Considering the great similarity of the molecules, the composition of the substance and the results of the estimation with EPI Suite v4.10, Acid Red 131:1 is expected to release water/imbibition solvent by between 50 and 150 °C, followed by product decomposition between 282 and 375 °C (onset at 307.5 °C, enthalpy: 113.9 J/g).

The smile notations used for the estimations are:


Sodium salt


Acidic form