Glycin is a photographic developing agent used in classic black-and-white developer. When fresh, it is typically characterized as thin plates of white or silvery powder, turning brown with age. It is sparingly soluble in water and most organic solvents; it is readily soluble in alkalies and acids.
Glycin is related to Metol. Compared to Metol, glycin has a carboxyl group attached to the methyl group of the Metol. This weakens the reduction potential of the compound, and the two developers have markedly different character. Glycin is slower-acting, but much longer-lasting in solution. Glycin is rarely used as a developing agent today, primarily because it is expensive and manufactured for specialty applications only. In its dry form, it also has limited shelf life compared to Metol and Phenidone.