Mercuric orthoarsenate

Mercurous orthoarsenate yields orange rhombic prisms which are insoluble in water. Hydrochloric acid converts it into calomel and arsenic acid. 

Mercuric Orthoarsenate, Hg8(As04)2, is obtained by precipitating a solution of mercuric nitrate with a solution of sodium mono- or dihydrogen arsenate, or by dropping aqueous arsenic acid into excess of mercuric nitrate solution.4 It is a heavy citron-yellow powder. Hot water dissolves it slightly without decomposition, and shining crystals may separate from the cooled solution. Hydrochloric acid dissolves it freely, nitric acid less readily, and arsenic acid not at all. Brine solution converts it into red-brown mercury oxychloride. Potassium bromide solution colours it brown, and a yellow residue is ultimately left. Potassium iodide forms mercuric iodide. 

Basic mercuric sulphate is converted into mercuric orthoarsenate and mercuric oxide by warming with sodium mono hydrogen arsenate solution. Hot acetic acid will extract the oxide.5... 

Colloidal mercuric orthoarsenate has been prepared9 by adding... 

In addition to the basic double salt with mercurous nitrate mentioned on p. 212, a double salt of composition HgsAs04.2HgN03.2H20 has been described as separating in warty masses or needle-shaped crystals when a solution of mercurous monohydrogen orthoarsenate in concentrated nitric acid is diluted with its own volume of water and then treated with aqueous ammonia and allowed to stand for a time.8... 

Synonyms cas 7784-37-4 mercury arsenate mercury orthoarsenate Mercuric Chloride... 

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