Page 2 :
LEARNING PLUS, (a) Function of Rochelle salt in Fehling solution. We know, that Cu2+ ions form a precipitate of Cu(OH)2 in alkaline, solution. To retain Cu?* ions in alkaline solution, Rochelle, salt is added. It combines with Cu(OH), to form a soluble, complex between Cu2+ lons and tartarate ion and thus,, goes in solution., НО СН СОО Na, Cu (OH)2 + 2, HO-CH COO K, H., HO-C-CO0, OOC - C-OH, Cu 2+, Cu, HO-C-COO, OOC- C-OH, H., + 2 NaOH + 2KOH, (b) Fehling solution and Benedict's solution are weak, oxidising agents. They oxidise only aliphatic aldehydes,, but do not oxidise aromatic aldehydes., (c) a-Hydroxy ketones give positive test with Tollen's reagent, and Fehling solution.