Sodium carbonate, commonly known as washing soda, is a white, crystalline powder. This color is due to its chemical composition, which includes sodium, carbon, and oxygen atoms arranged in a specific molecular structure. The white color is consistent across various forms of sodium carbonate, whether it is in its anhydrous (dried) or hydrated state. This characteristic color is important in its identification and usage in various industrial applications, such as in the manufacturing of glass, detergents, and paper. The purity of sodium carbonate is also indicated by its color, with higher purity levels typically resulting in a brighter white appearance.

The white color of sodium carbonate is a result of its chemical properties. It is an ionic compound, meaning it consists of positively charged sodium ions (Na+) and negatively charged carbonate ions (CO3^2-). These ions are arranged in a crystal lattice structure that reflects light in a way that gives the compound its characteristic white color. The color is not influenced by the presence of water molecules in the hydrated form of sodium carbonate, as the color remains white even when the compound is in its dehydrated state. This consistency in color across different forms of sodium carbonate is a key factor in its identification and use in various industries.