Caesium hydrogen carbonate, CsHCO₃

The primary carbonate is formed by the action of carbon dioxide on the normal carbonate, and crystallizes in long, anhydrous prisms, stable up to 125° C., but decomposing at 175° C. with evolution of carbon dioxide and formation of the normal carbonate. At 20° C. its solubility is higher than that of the corresponding potassium salt, being 67.77 grams in 100 grams of water: that of potassium hydrogen carbonate is 33.2 grams. At 15° C. the heat of solution is -4.317 Cal. The heat of formation from the elements is 232.92 Cal. The dissociation-pressure has been studied by Caven and Sand. Other primary carbonates are formed by the action of atmospheric carbon dioxide on a solution of caesium carbonate.