Copper deposits are sometimes seen in tissues from pathological conditions. They may be demonstrated with rubeanic acid, albeit with variable success.
The commonest current use for copper is small copper shot, placed into protargol solutions in Bodian type impregnations as an activator. Although considered to be a useful technique for demonstrating nerve fibres, this method is not the most popular.
Copper salts have been recommended for inclusion in preservatives at low concentrations, presumably because of copper's bacteriostatic nature. They have been included in fixatives and may also be used as mordants for hematein, where they are reputed to produce intense black staining. They may also mordant other dyes. Although recommended in the past for these purposes, in modern practice copper salts are not used in human histology to any appreciable degree.