[en] Dimethylsulfoxide is used as a solvent for the growth of red mercuric iodide (HgI2) crystals for use in radiation detectors. The hygroscopic property of the solvent allows controlled amounts of water to enter into the solvent phase and diminish the large solubility of HgI2 so that the precipitating solid collects as well-defined euhedral crystals which grow into a volume of several cc