Potassium Ferrocyanide [K4Fe(CN)6] or "Green salt" is an inorganic compound. It consists of potassium, iron, carbon, and nitrogen. It is also known as yellow potash prussiate (a yellow crystal). It was first discovered by French chemist Pierre Joseph Macquer in 1752 by reacting Prussian blue (C18Fe7N18 ) and potassium hydroxide (KOH). Sometimes it is used for the detection of metals in the analytical laboratory. In this article, we will discuss potassium ferrocyanide, its properties, and its applications in detail.