Hydroxide
The solubility in water of the other hydroxides in this group increases with increasing atomic number. Magnesium hydroxide Mg(OH) is a strong base (up to the limit of its solubility, which is very low in pure water), as are the hydroxides of the heavier alkaline earths: calcium hydroxide, strontium hydroxide, and barium hydroxide. A solution or suspension of calcium hydroxide is known as limewater and can be used to test for the weak acid carbon dioxide. The reaction Ca(OH) + CO Ca + + OH illustrates the basicity of calcium hydroxide. Soda lime, which is a mixture of the strong bases NaOH and KOH with Ca(OH), is used as a CO absorbent.
Acetate
When part of a salt, the formula of the acetate ion is written as , , or . Chemists often represent acetate as OAc or, less commonly, AcO. Thus, HOAc is the symbol for acetic acid, NaOAc for sodium acetate, and EtOAc for ethyl acetate. The pseudoelement symbol "Ac" is also sometimes encountered in chemical formulas as indicating the entire acetate ion (CHCO), or the acetyl group (CHCO). It is not to be confused with the symbol of actinium, the first element of the actinide series; context guides disambiguation. For example, the formula for sodium acetate might be abbreviated as "NaAc", rather than "NaCHO". Care should also be taken to avoid confusion with peracetic acid when using the OAc abbreviation; for clarity and to avoid errors when translated, HOAc should be avoided in literature mentioning both compounds.