white precipitate
now rare
noun
Any of various compounds of mercury occurring as white solids; (in later use) specifically (more fully infusible white precipitate) mercury amide choride (HgNH2Cl), which has a polymeric structure and has been used medicinally, and (more fully fusible white precipitate) mercuric chloride diammoniate (Hg(NH3)2Cl2).
Origin
Late 16th century; earliest use found in William Clowes (d. 1604), surgeon.