Collier's New Encyclopedia (1921)/Albumen

ALBUMEN or ALBUMIN. (1) In chemistry, the name of a class of albuminoids that are soluble in water, as serum and egg albumen. Egg albumen differs from serum by giving a precipitate when agitated with ether; it is scarcely soluble in strong nitric acid; its specific relation is 35.50 for yellow light. The white of eggs is composed of this substance; it dries up into a light yellow gum-like substance, which will not putrefy. It is an antidote in cases of poisoning by corrosive sublimate or copper salts.

Derived albumens are insoluble in water, and in solutions of NaCl (sodium chloride), but soluble in dilute acids and alkalies. There are acid albumens and alkali albumens.

Acid albumen is formed by adding a small quantity of dilute HCl (hydrochloric acid) to serum or egg albumen, and gradually raising the temperature to 70°.

Alkali albumen, or albumenate, is obtained by adding very dilute caustic alkali, heating the liquid, and precipitating with acids. It closely resembles the casein of milk. Potassium albuminate is also called protein.

(2) In botany, a substance interposed between the embryo and the testa of many plants. It varies greatly in amount, being particularly large in some endogens, such as the cocoanut, in which it constitutes the eatable part of the fruit.

(3) In photography, a process by which albumen is used instead of collodion to coat glass or paper.