Sodium carbonate, commonly known as washing soda, is a white, crystalline powder. This coloration is due to the compound's chemical structure, which consists of sodium ions (Na+) and carbonate ions (CO3^2-). The white color is a characteristic of many inorganic compounds and is a result of the way light interacts with the molecular structure of sodium carbonate.

The color of sodium carbonate is consistent with the data from various scientific studies. For instance, the CRC Handbook of Chemistry and Physics lists sodium carbonate as a white solid, and the same is true for the MSDS (Material Safety Data Sheet) for sodium carbonate, which is a standard document used to provide information on the properties and hazards of chemicals. The white color is also observed in the literature on inorganic chemistry, where sodium carbonate is often used as a reference compound. The color remains white regardless of the form of sodium carbonate, whether it is in its anhydrous (dried) or hydrated state. The hydration state can affect the physical properties such as solubility and crystalline form, but the color remains white.