Carbon dioxide test, Photo 3 of 4. Lime water is a saturated calcium hydroxide (Ca(OH)2) solution. When carbon dioxide (CO2) is bubbled through lime water, calcium carbonate (CaCO3) precipitates out of the solution giving the solution a cloudy appearance. The reaction is: Ca(OH)2(aq) + CO2(g) -> CaCO3(s) + H2O(l). This series shows the solution becoming progressively cloudy as carbon dioxide is being bubbled through a drinking straw. Image 3 of 4.