Formalin is a fixation solution suitable for the preparation of histological specimens. It consists of 40% formaldehyde (4% w/w), diluted in distilled water at a 1/10 ratio and buffered to a pH of 7. As a fixative, Formalin provides the inactivation of the autolytic enzymes and bacteria that cause the putrefaction of tissues and the provision of structural stability to the chemical components of the protoplasm.