Calcium carbonate equilibrium pressure must exceed total atmospheric pressure of 101 kPa, which happens at 898 °C. Calcium carbonate is poorly soluble in pure water (47 mg/L at normal atmospheric CO partial pressure as shown below). The equilibrium of its solution is given by the equation (with dissolved calcium carbonate on the right): where the solubility product for [Ca] [CO] is given as anywhere from "K" = 3.7×10 to "K" = 8.7×10 at 25 °C, depending upon the data source. What the equation means is that the product of molar concentration of calcium ions (moles of dissolved Ca per liter of solution)
Calcium iodide in the air, liberating iodine, which is responsible for the faint yellow color of impure samples. Calcium iodide Calcium iodide (chemical formula CaI) is the ionic compound of calcium and iodine. This colourless deliquescent solid is a salt that is highly soluble in water. Its properties are similar to those for related salts, such as calcium chloride. It is used in photography. It is also used in cat food as a source of iodine. Henri Moissan first isolated pure calcium in 1898 by reducing calcium iodide with pure sodium metal: Calcium iodide can be formed by treating calcium carbonate, calcium