Istihalat

Istihalat means change or, more precisely, a chemical change. It is the transformation or conversion from one material to another. It can be defined as a complete physical and/or chemical transformation that changes color, taste, odor, physical appearance, or material state. Something impure or najis  can become pure (tahir) by chemically changing into another element. Some examples of something impure that transforms into something pure are: urine evaporating and becoming vapor later becomes liquid; the body of a animal thrown into a salt mine becomes salt; manure made from animal excrement, which after going through a long process becomes fertilizer for the earth.

Another good example is the chemical transformation to generate the ester. Ester is obtained from an esterification reaction. This kind of reaction occurs between a carboxylic acid and an alcohol, forming water (besides the ester itself). The esters, even being from alcohol, are Halal food because the residual of the alcohol in the final product is minimum or inexistent.