This is a colorimetric laboratory reagent which measures the enzyme alkaline phosphatase in the human body by the colorimetric method. Acid Phosphatase is an enzyme of the hydrolase class of enzymes and acts in the acidic medium. It is widely distributed in the body and is found in the liver, RBC and prostrate. Increased level of the prostatic fraction is associated with prostatic carcinomas. Increased levels of the non prostatic fraction is associated with liver disease,hyperparathyroidism and Paget’s disease. ACP at an acidic pH hydrolyses di Sodium Phenyl phosphate to form phenol. The phenol formed reacts with 4- Amino antipyrine in the presence of Potassium Ferricyanide as an oxidising agent to form a red coloured complex. The intensity of the colour formed is directly proportional to the activity of the ACP present in the sample. Tartarate inhibits prostatic ACP and testing in it’s presence is done to find out non prostatic ACP. The difference in the activities of total ACP and non – prostatic ACP gives the activity of the prostatic ACP.