Prep. The white of one egg is well triturated in a mortar with four ounces of distilled water, and filtered through clean tow, previously moistened with distilled water.

Use. This is used for testing phosphoric acid. The phosphoric acid, which is the tribasic variety, is not precipitated by albumen, this test distinguishes it from the monobasic phosphoric acid; both the monobasic and bibasic varieties give white precipitates with nitrate of silver, but the latter does not precipitate albumen, while the former does. Creosote also coagulates the solution of albumen, which property is given in the Pharmacopoeia as one of its characteristics.