蓝印 (blueprint) 系铁盐照相的一种,广泛用于工程图复制。十九世纪中期由J.Herschel发明。它利用三价铁盐光照生成两价铁盐,后者再与其它物质反应生成有色产物。一般用草酸铁,铁氰化钾及柠檬酸(或草酸)作为感光成分。曝光时进行如下反应: Fe_2~(3+)(C_2O_4)_3(?)2Fe~(2+)+(CaO_4)+2CO_2 Blue print (blueprint) is a kind of iron salt photography, widely used in engineering drawings. The mid-nineteenth century by J.Herschel invented. It utilizes trivalent iron salts to generate divalent iron salts, which react with other materials to form colored products. General use of iron oxalate, potassium ferricyanide and citric acid (or oxalic acid) as a photosensitive component. During the exposure, the following reaction is carried out: Fe 2 - (3 +) (C 2 O 4) 3 (?) 2Fe 2 + + (CaO 4) + 2CO 2