Fig. 76
Properties. Sodium is a silver-white metal about as heavy as water, and so soft that it can be molded easily by the fingers or pressed into wire. It is very active chemically, combining with most of the non-metallic elements, such as oxygen and chlorine, with great energy. It will often withdraw these elements from combination with other elements, and is thus able to decompose water and the oxides and chlorides of many metals.
Sodium peroxide (NaO). Since sodium is a univalent element we should expect it to form an oxide of the formula Na2O. While such an oxide can be prepared, the peroxide (NaO) is much better known. It is a yellowish-white powder made by burning sodium in air. Its chief use is as an oxidizing agent. When heated with oxidizable substances it gives up a part of its oxygen, as shown in the equation
2NaO = Na2O + O.
Water decomposes it in accordance with the equation
2NaO + 2H2O = 2NaOH + H2O2.
Acids act readily upon it, forming a sodium salt and hydrogen peroxide:
2NaO + 2HCl = 2NaCl + H2O2.
In these last two reactions the hydrogen dioxide formed may decompose into water and oxygen if the temperature is allowed to rise: