In metallurgy, refining consists of PURIFYING an impure metal. It is to be distinguished from other processes such as smelting and calcining in that those two involve a chemical CHANGE to the raw material, whereas in refining, the final material is usually identical chemically to the original one, only it is purer. The processes used are of many types, including pyrometallurgical and hydrometallurgical techniques.Explanation:In order to isolate noble-metalliferous materials, pyrolysis and/or hydrolysis PROCEDURES are used. In pyrolysis, the noble-metalliferous products are released from the other materials by solidifying in a melt to become cinder and then poured off or oxidized. In hydrolysis, the noble-metalliferous products are dissolved either in aqua regia (consisting of hydrochloric acid and nitric acid) or in hydrochloric acid and chlorine gas in solution. Subsequently, certain metals can be precipitated or reduced directly with a salt, gas, ORGANIC, and/or nitro hydrate connection. Afterwards, they go through cleaning stages or are recrystallized. The precious metals are separated from the metal salt by CALCINATION. The noble-metalliferous materials are hydrolyzed first and thermally prepared (pyrolysed) thereafter. The processes are better yielding when using catalysts that may sometimes contain precious metals themselves. When using catalysts, the recycling product is removed in each case and driven several times through the cycle.Thanks for the question. Hope it helps you.