Sulfates can be subdivided into anhydrous and hydrous minerals. Several reductants are currently used in SCR applications including anhydrous ammonia, aqueous ammonia or urea. In addition to the anhydrous material, ferric chloride forms four hydrates. Anhydrous copper sulfate is a grey powder. The oil is dried by mixing it with a small amount of anhydrous calcium chloride. The compound adopts the structure seen for anhydrous sodium sulfate. For example, an aqueous solution prepared from CuSO and anhydrous CuSO behave identically. Tin(II) hydroxide Sn(OH) was prepared in anhydrous media. Dissolution is also different for anhydrous and hydrous forms of a drug. Reaction of the anhydrous compound with sodium cyclopentadienide gives cobaltocene . Substitution of urea can reduce costs and potential hazards associated with storage of anhydrous ammonia. Barium carbonate is often added to maintain anhydrous and acid-free conditions. Fe is in oxides, hydrous, anhydrous, and in glauconites. Anhydrous copper(II) sulfate is a white solid. Fluoroantimonic acid is made by dissolving antimony pentafluoride (SbF) in anhydrous hydrogen fluoride (HF).