Riba equal quantities of the same kind of commodity ("like for like") — for example 100 kilograms of wheat for 100 kg of wheat — in a riba-free transaction called for by quoted ahadith. Or how "divine law" could prescribe that a jeweler — "who has spent his time and effort to convert gold into jewelry" and is taking gold as payment — not be compensated? M.A. Khan also notes that the authors of the IIIE blueprint have no objection to traders selling higher purity/quality commodity for cash and using the proceeds to buying more less purity/quality commodity, and wonders what
Industrial separation processes which restricts the movement of one compound but not of the other one (semipermeable membranes) is less common; external fields are used just in special applications. Industrial separation processes Industrial separation processes are technical procedures which are used in industry to separate a product from impurities or other products. The original mixture may either be a natural resource (like ore, oil or sugar cane) or the product of a chemical reaction (like a drug or an organic solvent). Separation processes are of great economic importance as they are accounting for 40 – 90% of capital and operating costs in industry.