X-ray fixer contains all of the following except:

An accelerator: X-ray fixing solution contains the following: * A clearing agent, such as sodium or ammonium thiosulfate, commonly called hypo, dissolves and removes the underdeveloped silver halide crystals from the emulsion. The chemical "clears" the film so that the black silver image produced by the developer becomes distinctly perceptible. W hen the film is improperly cleared, the remaining unexposed silver halide crystals darken upon exposure to light and obscure the image. * An antioxidant preservative, for example sodium sulfite, prevents the decomposition of the fixer chemical. * An acidifier such as acetic acid, that is necessary for the correct action of the other chemicals and also neutralizes any alkaline developer that may be carried over by the film or hanger.