To prepare Fehling's reagent for the identification of aliphatic aldehydes, aqueous copper sulphate is mixed with an alkaline solution of a complexing agent. This agent prevents the precipitation of cupric hydroxide by forming a soluble complex. The complexing agent used is:

Step-by-step solution

Fehling's reagent is prepared by mixing two solutions: Fehling's A and Fehling's B. Fehling's A is an aqueous solution of copper sulphate ( CuSO ₄ ). Fehling's B is an alkaline solution of sodium potassium tartrate, which is also known as Rochelle salt. When these two solutions are mixed, the tartrate ions act as a chelating agent and form a soluble deep blue complex with the cupric ions ( Cu ²⁺ ). This complexation prevents the precipitation of cupric hydroxide ( Cu(OH) ₂ ) in the strongly alkaline medium. Therefo