Kligler Iron Agar is used for differentiating Gram-negative bacilli based on the fermentation of Dextrose and Lactose. This medium is also used in the production of hydrogen sulfide. Peptic Digest of Animal Tissue and Enzymatic Digest of Casein provide nitrogenous compounds, carbon, and vitamins. Dextrose and Lactose are the fermentable carbohydrates. Ferric Ammonium and Sodium Thiosulfate allow for the detection of hydrogen sulfide production. Phenol Red is the pH indicator that indicates carbohydrate metabolization. Sodium Chloride maintains the osmotic balance. Agar is the gelifying agent.