Also known as spirit of nider, what reacts with proteins to form yellow products?
Xanthoproteic acid Xanthoproteic acid is a noncrystallizable yellow substance derived from proteins upon treatment with nitric acid. 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 are present that contains amino acids with aromatic rings, the mixture turns yellow. Upon adding a strong base such as liquid ammonia, the color turns orange. These color changes are caused by nitrated aromatic rings in the protein. The xanthoproteic test is specific for aromatic compounds such as tyrosine, tryptophan and phenyalanine.
Heptasulfur imide Heptasulfur imide is the inorganic compound with the formula SNH. It is a pale yellow solid that is, like elemental sulfur, highly soluble in carbon disulfide. The compound, which is only of academic interest, is representative of a family of sulfur imides S(NH).