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Physical & Chemical properties

Dissociation constant

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Description of key information

ZMBT is an organic complex and its aqueous solution is a balance of weak

base Zn(OH)2 and weak acid of MBT. The ionisation state depends upon pH and the pKa of each half. The pKa of MBT has been experimentally determined to be 7.03 at 20 +/-1°C (CMA, 1989). The pKb of Zn(OH)2 is known as ca. 3, which is lower than the pKa of MBT; and hence the aqueous solution of ZMBT should have a basic character and the dissociation property of ZMBT is mainly determined by the one of MBT. Under environmentally relevant pHs (4 -9), the higher is the pH and the higher is the percentage of undissociated MBT.

Key value for chemical safety assessment

pKa at 20°C:
7.03

Additional information

Result from MBT