Name three important reagents necessary for the preparation of potassium
Assuming you meant Potassium hydroxide (because we cannot manufacture Potassium metal), the only reagent is Potassium chloride.
Potassium hydroxide is made by the electrolysis of an aqueous solution of potassium chloride (KCl). In the process, an electric current decomposes potassium chloride into potassium and chlorine. The chlorine escapes as a gaseous by-product and the potassium reacts with water to form potassium hydroxide.