Actually, I just double-checked the solubility of lactose in water; it's only 195 g/L at 25 °C. For reference, glucose (dextrose) is 905 g/L, and sucrose (table sugar) is about 2000 g/L.
So, if you put 454 g of lactose into 0.24 L of water, you're way over the saturation point at room temperature. Obviously, the solubility will go up with temperature, but I am not sure you can even dissolve 454 g lactose in 0.24 L water.