Consider the case of nickel(II) chloride hexahydrate. The most common form of the trichloride is the dark green hexahydrate, CrCl. The yellow-green crystals of dioxouranium nitrate hexahydrate are triboluminescent. The hexahydrate and the anhydrous salt are weak Lewis acids. NMR spectroscopy indicates that solutions derived from this hexahydrate contain significant amounts of HF. Nickel sulfate occurs as the rare mineral retgersite, which is a hexahydrate. STPP is a colourless salt, which exists both in anhydrous form and as the hexahydrate. In fact, samples of ScCl converts to this hexahydrate upon exposure to air. NiCl-dme (or NiCl-glyme) is used due to its increased solubility in comparison to the hexahydrate. Calcium chloride occurs as the rare evaporite minerals sinjarite (dihydrate) and antarcticite (hexahydrate). The anhydrous salt is hygroscopic and the hexahydrate is deliquescent. The main hexahydrate can be more precisely described as [CrCl(HO)]Cl. A form in which piperazine is commonly available industrially is as the hexahydrate, CHN. Topical hyperhidrosis gels containing aluminum chloride hexahydrate are usually first choice treatments for this condition. One popular brand includes 10% total strontium chloride hexahydrate by weight.