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Physical & Chemical properties

Water solubility

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Description of key information

measured:
28.35% (w/w) (this is ca. 346.15 g TMT anhydrous/L solution) at 22 °C and pH>10.1
QSAR:
≥ 1.8 g/L at pH4
≥ 9.7 g/L at pH7
≥ 350 g/L at pH9
≥ 1370 g/L at ≥pH9.9

Key value for chemical safety assessment

Water solubility:
346.15 g/L
at the temperature of:
22 °C

Additional information

The water solubility of TMT anhydrous was determined in a flask test, which meets basic scientific principles, to be 28.35 weight% at 22 °C (2011-0376-DKP). The pH value of the saturated solution is not explicitly given in the report, but due to the analytic method it should be higher than pH 10.1. In addition, from another study, where the pH value of TMT 15 (aqueous solution with 15% TMT anhydrous) was determined to be 12.3, it can be concluded that the pH of the 28.35% solution is also very high.

From this result and the measured density of this saturated solution (1.221 g/mL) a water solubility of 346.15 g/L at 22 °C can be concluded.

This result is supported by QSAR calculation: The water solubility of the trisodium salt could not directly be estimated by QSAR (2012-0406-DKB). Therefore the water solubility of the protonated forms was calculated by the ACD program. The estimation is valid for the organic acid and its sodium salts. The pH dependence of the solubility value results from the pH dependence of the ratio between the concentrations of the undissociated organic acid and the ionic species formed from the neutral acid.

Both tautomeric forms were investigated. Keto form: The solubility in water increases with pH from pH 4 (1.82 g/L) to pH 14 to 1370 g/L. The solubility will not change at pH 9.9 (1370 g/L). Enolic form: The solubility in water increases with pH from pH 0 (27.72 g/L) and with pH 1.5 the maximum of 1370 g/L will be reached. TMT anhydrous is very soluble in water.

These results are supported by a further water solubility study of the substance, which was performed by an internal lab method (88-0986-DKP). The water solubility of TMT anhydrous is given as 25 weight% at 20 °C (that is ca. 305 g/L) and 27 weight% at 25 °C (that is ca. 330 g/L). The documentation of this water solubility study is insufficient for assessment as no method of analytic and no method of determination of the density is given. Nevertheless this study is in good agreement with the key value and the QSAR results.