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Partition coefficient

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Description of key information

Tartaric acid and its salts are hydrophilic (i.e. they show high polarity).

All LogKow were < 0.

Key value for chemical safety assessment

Additional information

A collection of the partition coefficients was performed for tartaric acid and its salts. As result, some values specifically referred to tartaric acid amd calcium tartrate were found. These values were similar and support the hydrophilicity of the substance (i.e. all LogKow were < 0).

For tartaric acid Log Kow (OECD 107) is -1.91 at 20°C.

For calcium tartrate the measurement of the octanol/water coefficient was difficult to achieve. At pH < 2, recovery of calcium tartrate in the water phase was not total, suggesting that calcium tartrate in the octanol phase was not negligible. Unfortunately the developed IC method for the quantification of calcium tartrate in water was proved not to be convenient for the octanol phase. The amount of calcium tartrate in the octanol phase was calculated on the basis of total added amount minus measured amount in the water phase, while postulating that recovery of calcium tartrate in the two-phase system should be total. Depending on whether thenominal added amount or the measured added amount was taken into account, the mean value for Log Pow was calculated as -1.46 or -1.85.

At both pH = 7 and pH = 9 recovery of Calcium tartrate in the water phase was almost total, and the conclusion was that the quantification of Calcium tartrate in the octanol phase was not feasible.

The octanol/water partition coefficient was estimated on the basis of the ratio of the solubility of Calcium tartrate in each octanol and in water at the required pH value.

Log Pow at pH 7 = -3.6 a 20 °C

Log Pow at pH 9 = -3.7

Since the partition coefficient of tartaric acid is extremely low and taking into account the chemistry of its salts (i.e. their water solubility), it is believed that also the tartaric acid salts should not behave differently.

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