Also known as 5-Bromo-4-Chloro-3-Indolyl Phosphate. A widely used chromogenic substrate for alkaline phosphatase in enzyme-linked assay systems. BCIP may be used alone, or may act in a coupled reaction with NBT. Upon cleavage of the phosphate group from the molecule, BCIP forms a bright blue, insoluble product. This product then reacts to form a chromogen homodimer. This reaction may be used to amplify the signal by catalyzing the reduction of a tetrazolium salt (usually NBT) to form an intensely colored, insoluble formazan chromogen.