Albumin
This name is given to a group of proteins which are soluble in water. Albumin is an organic body of very great complexity. It is better for present purposes to give examples of substances containing albumin which can be easily recognized than to try to describe its properties and structure at length.
Egg albumin is found in the white of an egg; meat contains myosin; milk, caseinogen; cheese, casein. Heating, and boiling albumin with water, causes it to coagulate, a phenomenon which can well be seen in the boiled egg.
Albumins generally are water-soluble before coagulation, but after coagulation can only be dissolved by a causdc alkali (sodium hydroxide solution) or a mineral acid (dilute nitric or hydrochloric acid, for example).
Egg-stains on silver can be removed by rubbing with a little salt on the finger-tips.
Blood-stains contain albumin.
See Egg as Medium in Painting; Emulsion; Tempera.