Third Phase Formation
also known as third phase · organic splitting
Third phase formation occurs when the metal-extractant complex reaches a concentration at which it is no longer soluble in the diluent and separates out as a dense organic layer, giving three layers in the settler instead of two. It is most common at high loading, low temperature, and with heavily loaded acidic extractants in aliphatic diluents.
Why it matters in practice
A third phase destroys the circuit's mass balance because it removes organic from circulation and its position in the settler can invert the phase continuity, pulling aqueous out with the organic. Adding a modifier such as a long-chain alcohol or operating at lower loading are the standard remedies.
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Related terms
Reference entry GL-THIRD-PHASE. Definitions on this page describe engineering practice in hydrometallurgical process design; they are not a substitute for test work on your own material.