Ammonia is a compound of nitrogen with the formula NH3. It is a colorless gas with a characteristic pungent smell. Ammonia contributes significantly to the nutritional needs of terrestrial organisms by serving as a precursor to food and fertilizers. Ammonia, either directly or indirectly, is also a building block for the synthesis of many pharmaceuticalsand is used in many commercial cleaning products. Although in wide use, ammonia is both caustic and hazardous.