Tawas itu ada berbagai macam 1. Tawas Kalium (rumus molekulnya KAl(SO4)2)Sifat fisikaMassa molar = 258.21 g/molDensitas = 1.76 g/cm3Titik leleh = 92–93 °CTitik didih = 200 °CKelarutan dalam air = 36.80 g/100 g (50 °C)

2. Tawas Soda (rumus molekulnya NaAl(SO4)2·12H2O)Sifat fisikaMassa molar = 458.28 g/molDensitas = 1.6754 (20 °C)Titik leleh = 61 °CIndeks bias = 1.4388Kelarutan dalam air =208 g/100 ml (15 °C)

3. Tawas amonium (rumus molekulnya (NH4)Al(SO4)2)Sifat fisikaMassa molar = 237.15 g/mol (anhydrous)453.33 g/mol (dodecahydrate)Densitas = 2.45 g/cm3 (anhydrous)1.64 g/cm3 (dodecahydrate)Titik leleh = 93.5 °C (dodecahydrate)Titik didih = 120 °C (dodecahydrate)Solubility in water = 15 g/100 ml (20 °C, dodecahydrate)

4. Tawas krom (rumus molekulnya KCr(SO4)2)Sifat fisikaMassa molar = 499,246 g/molDensitas = 1.83 g/cm3Titik leleh = 89 °CKelarutan dalam air = 244 g/100 g (25 °C)