Registration Dossier

Diss Factsheets

Physical & Chemical properties

Dissociation constant

Currently viewing:

Administrative data

Link to relevant study record(s)

Description of key information

The dissociation constants of the substances in the lithium salts of monocarboxylic acids category have been read across from the respective acids (measured as potassium or sodium salts). The acids (as potassium salts (from Kanicky 2002) or sodium salts (Kanicky 2000)) have measured pKA values of 8.1-8.2 (C14, sodium salt), 8.6-8.6 (C16, sodium salt), 9.24 (C18”, potassium salt), 9.85 (C18’, potassium salt) and 10.15 (C18, potassium salt). These values are relatively high, therefore these carboxylate substances are expected to be in the salt (ionic) form at environmental pH.

Key value for chemical safety assessment

Additional information

The substances are all lithium salts of monocarboxylic acids. Aqueous solutions of the substances are therefore expected to dissociate to free metal ions and carboxylic acid ions. The carboxylic acid ions would then be expected to achieve acid-base equilibrium, depending on the pKA of the carboxylic acid, at the pH of the solution. The dissociation constant of the substance is effectively represented by the dissociation constant(s) of the relevant carboxylic acid, as the ionisable moiety. As the monocarboxylic acids and the lithium salts of monocarboxylic acids are not soluble in water, data have been read across from the acids tested as potassium or sodium salts, which have higher solubility.

Reliable measured data available in the published literature for the dissociation constants of sodium and potassium salts of the relevant monocarboxylic acids have been used to complete this endpoint (Kanicky 2000, 2002): sodium myristate (C14), sodium palmitate (C16), potassium linoleate (C18”), potassium oleate (C18’) and potassium stearate (C18). The substances have measured pKA values of 8.1-8.2 (C14), 8.6-8.6 (C16), 9.24 (C18”), 9.85 (C18’’) and 10.15 (C18). These values are relatively high, therefore these carboxylate substances are expected to be in the salt (ionic) form at environmental pH.

Further investigations on the dissociation constant of lithium 12 -hydroxystearate are currently ongoing.

Categories Display