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Physical & Chemical properties

Dissociation constant

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Description of key information

There are two different sources of information available which are used in a weight-of-evidence approach. In the CRC Handbook of Chemistry and Physics the dissociation constant of thiourea at 25 °C is stated to be pKa = –1. Data on the determination dissociation constant according OECD guideline 112 of the sponsor showed that  pka-value is not determinable because Thiourea forms no OH or H ions.

Key value for chemical safety assessment

Additional information

According the CRC Handbook of Chemistry and physics the dissociation constant of thiourea at 25 °C is pKa = –1.

In another study provided by the sponsor the dissociation constant of Thiourea was determined according to OECD guideline no. 112 with the titration method at 24 °C. It was shown that the pka-value was not determinable because Thiourea forms no OH or H ions. This study is chosen as key value as an experimental result has a higher reliability than handbook data.