Microcosmic salt is a salt found in urine

Urine

Urine is a typically sterile liquid by-product of the body that is secreted by the kidneys through a process called urination and excreted through the urethra. Cellular metabolism generates numerous by-products, many rich in nitrogen, that require elimination from the bloodstream...

 with the formula (NH₄)NaHPO₄. In the mineral form, microcosmic salt is called stercorite

Stercorite

Stercorite is the mineral form of microcosmic salt. The name comes from the Latin "stercus", meaning dung, since the mineral was originally discovered among guano....

.

The first extraction of pure phosphorus

Phosphorus

Phosphorus is the chemical element that has the symbol P and atomic number 15. A multivalent nonmetal of the nitrogen group, phosphorus as a mineral is almost always present in its maximally oxidized state, as inorganic phosphate rocks...

 came from this salt, when Hennig Brandt attempted to extract gold

Gold

Gold is a chemical element with the symbol Au and an atomic number of 79. Gold is a dense, soft, shiny, malleable and ductile metal. Pure gold has a bright yellow color and luster traditionally considered attractive, which it maintains without oxidizing in air or water. Chemically, gold is a...

 from urine.

Microcosmic salt is used in the laboratory as an essential ingredient of the microcosmic salt bead test for identification of metallic radicles on the basis of the color they produce in oxidising or reducing flame, in hot or cold condition.

Microcosmic salts form a tetrahydrate.