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Physical & Chemical properties

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Urea is a non-flammable, crystalline solid with a melting point between 133.3 -134 °C. The substance is reported to decompose before the boiling point is reached (CRC Handbook, 2006). The density and vapour pressure of urea was measured to be 1.33 g/cm³ (Gwerder et al, 2009) and 1.2 x 10-5mmHg at 25 °C (Jones, 1960) respectively. Urea is very water soluble and has a partition coefficient of -1.56. The dissociation constant of urea (pKb) is reported to be 0.10 at 21 °C (Perrin, 1965) and is measured to be lower than 0.6 in a modern proprietary study (Gwerderet al, 2009). Urea is not predicted to have any oxidising properties based on a theoretical assessment of its chemical structure.