Hawzah News Agency – If a canonically impure substance undergoes a substantial change that causes it to turn into a different substance—such as if a canonically impure stick burns and turns to ash, wine turns to vinegar, or the carcass of a dog in a salt flat transforms into salt—it becomes canonically pure. If, however, it does not undergo such a substantial transformation but only changes in form—such as if impurified wheat is ground into flour or impurified sugar is dissolved in water—it does not become canonically pure.

Source: https://www.leader.ir/en/book/32/Practical-Laws-of-Islam