Microcosmic salt

Microcosmic salt (see infobox for systematic names) is a salt found in urine with the formula Na(NH4)HPO4. It is left behind in the residues after extracting the urea from dried urine crystals with alcohol. In the mineral form, microcosmic salt is called stercorite.

Its name was coined in Latin (sal microcosmicum) by Paracelsus in the 16th century, but it was also referenced by Pseudo-Geber in the late Middle Ages; another alchemical name for it was sal urinae fixum (as opposed to sal urinae volatile). The first extraction of pure phosphorus came from this salt in the 17th century, when Hennig Brandt attempted to extract gold from urine.

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

Microcosmic salts form a tetrahydrate.