Preparation of copper(I) tetraiodomercurate(II)
Mercuric iodide is precipitated by mixing solutions con taining 6.8g of mercuric chloride and 8.3g of potassium iodide. The washed material is dissolved in 50ml of water containing a similar quantity of potassium iodide, and mixed with a saturated aqueous solution of 12g of copper sulfate 5-hydrate. A stream of sulfur dioxide is passed into the mixture until precipitation is complete and the supernatant liquid is very faintly colored. The deep red salt is filtered off, washed with water, and irrigated with 50ml of acetone to facilitate drying in warm air. Yield about 20g. By means of a melting point capillary and a water bath, the transition point from red to black is easily observed. The procedure may be hastened by pre-heating the bath to about 65°C.
Inorganic laboratory preparations, by G. G. Schlessinger, 88-89, 1962