Can liquids other than water be purified?
Chapter on what purification is achieved with regarding water
Al-Mughni
Book of Purification
Primary text
In the view of Al-Qadi and Ibn Aqil, no liquid other than water can be purified through purification methods. Ibn Aqil specifically notes that mercury is an exception because of its strength and cohesion, making it function like a solid. This is based on the narration where the Prophet, peace be upon him, was asked about fat in which a mouse fell, and he commanded them not to approach it if it was liquid, implying that if a means of purification existed, he would not have commanded its disposal.
Supporting text
Abu Al-Khuttab chose the view that substances capable of purification, like oil, can be purified because they can be washed with water, similar to solids. The method involves placing the substance in much water, agitating it until the water contacts all parts, letting it settle so the oil floats, and then removing it. It is also permissible to leave it in a jar, pour water over it, agitate it, and provide an outlet for the water to drain. The rejection of purification might be due to the difficulty involved or the limited scope of the specific narration concerning fat, which might solidify in water.