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Physical & Chemical properties

Auto flammability

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Description of key information

Relative self ignition (HEBMP-H): No self-ignition temperature below 400°C (EU Method A.15) for sodium salt of the substance.

Key value for chemical safety assessment

Autoflammability / Self-ignition temperature at 101 325 Pa:
400 °C

Additional information

A reliable test on sodium salt of the substance conducting according to EU Method A.16 showed no relative self-ignition below 400˚C.

In solution, HEBMP-H (CAS 5995-42-6) undergoes a reversible internal condensation reaction to form a pH-dependent equilibrium mixture with the cyclised structure 4-(Phosphonomethyl)-2-hydroxy-2-oxo-1,4,2-oxaza-phosphorinane (CAS 32422-02-9, c-HEBMP) and water. The precise proportion of the two forms is dependent on pH, temperature and time, and under acidic or neutral conditions, the proportion of c-HEBMP in the multi-constituent substance may reach proportions as high as ≥50% w/w. Spectroscopic evidence from 31P-NMR analysis suggests that in the pH range ca. 1 – 7 a high proportion (50-75% w/w) is present as the cyclised form. The two forms exist in equilibrium therefore it is extremely difficult to separate and purify both forms. The properties of the whole substance, in which both forms are present at representative levels, are used in the chemical safety assessment.