Appearance: White or slightly yellow crystalline powder. Solubility: Freely soluble in 10% ethanol in water; soluble in solution containing surfactants in water or in 1%-10% ethanol; slightly soluble in water and in oil. The solubility in water varies by pH value, and is a litter larger in neutral or weak basic solution than in acid solution. PH: 8.5-10.0 (1% suspension in water, 20°C) PKa: 7.4 Melting range: 130-135°C