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Please be aware that this old REACH registration data factsheet is no longer maintained; it remains frozen as of 19th May 2023.

The new ECHA CHEM database has been released by ECHA, and it now contains all REACH registration data. There are more details on the transition of ECHA's published data to ECHA CHEM here.

Diss Factsheets

Physical & Chemical properties

Dissociation constant

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Administrative data

Link to relevant study record(s)

Reference
Endpoint:
dissociation constant
Type of information:
other: Literature
Adequacy of study:
key study
Study period:
1967
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: Published in peer-reviewed journal.
Qualifier:
no guideline available
Principles of method if other than guideline:
Chemicals used are of analytical grade. The dissociation constant of the metformin hydrochloride has been determined by pH–metric study. The hydrogen ion concentration is measured with a Systronics Model 335 pH-meter having glass/calomel electrodes and temperature probe. The electrodes are maintained at a constant temperature of 30 +/- 0.1°C. The pH-meter is calibrated directly in terms of hydrogen ion concentration at specific ionic strength (0.1 or 0.05 mol dm exp-3 potassium nitrate) using saturated potassium hydrogen phthalate at pH 3.55 and 0.05 mol dm exp-3 borax at 9.2 pH. All studies are carried out at 30 °C in an inert atmosphere using standard KOH solution at constant ionic strength.
GLP compliance:
no
Dissociating properties:
not determined
pKa:
ca. 11.61
Temp.:
30 °C

The pKa as reported in literature is 11.61 at 30.0 °C +/- 0.1 °C

Conclusions:
The pKa as reported in literature is 11.61 at 30.0 °C +/- 0.1 °C
Executive summary:

The pKa as reported in literature is 11.61 at 30.0 °C +/- 0.1 °C

Description of key information

Key value for chemical safety assessment

pKa at 20°C:
12.4

Additional information