Nitric acid concentrated acid and nitric oxide for dilute acid. or Concentrated nitric acid oxidizes I, P, and S into HIO, HPO, and HSO, respectively. Nitric acid reacts with proteins to form yellow nitrated products. This reaction is known as the xanthoproteic reaction. This test is carried out by adding concentrated nitric acid to the substance being tested, and then heating the mixture. If proteins that contain amino acids with aromatic rings are present, the mixture turns yellow. Upon adding a base such as ammonia, the color turns orange. These color changes are caused by nitrated aromatic rings in the protein. Xanthoproteic
Acid–base reaction Instead of defining acid–base reactions in terms of protons or other bonded substances, the Lewis definition defines a base (referred to as a "Lewis base") to be a compound that can donate an "electron pair", and an acid (a "Lewis acid") to be a compound that can receive this electron pair. For example, boron trifluoride, BF is a typical Lewis acid. It can accept a pair of electrons as it has a vacancy in its octet. The fluoride ion has a full octet and can donate a pair of electrons. Thus is a typical Lewis acid, Lewis base reaction. All