Astatine sublimes less readily than does iodine, having a lower vapor pressure. It is a colorless solid that readily sublimes into intensely yellow vapors. It is a colourless solid that is slightly soluble in water and sublimes readily. It melts at , boils at and sublimes easily. It is a colorless, diamagnetic solid that sublimes readily. Indigo dye is a dark blue crystalline powder that sublimes at . Uranium hexafluoride, a solid at room temperature, sublimes at at . The chemically bound water inside these materials sublimes. On approach to the Sun, the ice many comets carry sublimes to vapor. Acetylene is also the only other common industrial gas that sublimes at atmospheric pressure. When the pressure is below the triple point, solid nitrogen directly sublimes to gas. It possesses a disagreeable odor, sublimes readily, and turns brown on exposure to air. It is a dark purple solid that sublimes readily slightly above room temperature. When the reacting selenium is heated, the product sublimes from the reaction flask. It is a dark green solid that sublimes under vacuum.