Zinc chloride is the name of chemical compound ZnCl2 or its hydrates. All zinc chlorides are colorless or white and highly soluble in water. ZnCl2 itself is hygroscopic and can be considered deliquescent. Samples should therefore be protected from sources of moisture, such as the atmosphere. Four crystalline forms of ZnCl2 and its hydrates are known, although the anhydrous form appears to exist only in the hexagonal close-packed phase. Rapid cooling of molten ZnCl2 forms a glassy material. Concentrated aqueous solutions of zinc chloride have the interesting property of dissolving starch, silk, and cellulose. Thus, solutions of zinc chlorides cannot be filtered through standard filter papers. Zinc chloride finds wide application in textile processing, metallurgical fluxes and chemical synthesis.