Mercurous tantalate

Mercurous Tantalate, 4Hg20.3Ta205.5H20, is a greenish-yellow compound which is precipitated by mixing a mercurous salt and a tantalate in solution.2... 

Ligands are named first, starting with any anionic ones, and the name of the metal is followed without a space by the oxidation state in Roman numerals (or the Arabic 0, for zero-valent metal centers) in parentheses. If the complex as a whole is anionic, the metal name is made to end in -ate, which replaces endings such as -ium or -um (nickelate, chromate, tantalate) and is followed by the oxidation state. Where the chemical symbol is derived from a Latin name, the anion name is usually also Latinized cuprate, argentate, aurate, ferrate, stannate, plumbate—but mercurate is an exception. 

One of the most tantalizing chemical transformations known to ancient practitioners of inorganic chemistry involved roasting of mercuric sulfide ores such as cinnabar to form hydrargyrum or quicksilver (60). As the toxic properties of mercury became more widely appreciated in the middle ages, formulations of the metal and its salts were used in medical applications. 

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