Patent Blue V calcium salt (Standard) is the standard substance of Patent Blue V calcium salt, and it is applicable for quantitative analysis, quality control, and related research in biochemical experiments. Acid blue is a dark bluish synthetic triphenylmethane dye. It used as a food coloring. The color of the dye is pH-dependent. The structure is also redox-sensitive, changing from a reduced yellow form to an oxidized red form in solution. It is usable as a reversible redox indicator in some analytical methods.