Mercuric iodide red or mercury(II) iodide red is the alpha crystalline form of mercury(II) iodide and is available as a red colored powder. It is widely used for demonstrating thermochromism as it forms a yellow beta form of mercuric iodide when heated above 126 C. It is odorless and hardly soluble in water. It has a melting point of 259 C (498 F; 532 K) and boiling point of 350 C (662 F; 623 K). It is used in the synthesis of Nesslers reagent (used in the detection of ammonia). It is also used in x-ray and gamma ray detection and imaging devices operating at room temperatures. Quantity Provided: 25 gm/Bottle Molecular Weight: 454.40 Molecular Formula: HgI2 CAS No: 7774-29-0 Assay: Min. 99-100.5%