Does distilled water contain ions? This question arises from distilled water’s reputation for purity. Understanding its production clarifies what “pure” means regarding ion content.
Understanding Distilled Water
Distilled water is purified water produced by distillation. This involves boiling water into steam, then condensing it back into liquid in a separate container. Impurities in the original water, especially non-volatile ones, are left behind in the boiling vessel. This separates water molecules from dissolved contaminants.
The Nature of Ions
Ions are atoms or molecules that carry an electrical charge due to gaining or losing electrons. They can be positively charged (cations) or negatively charged (anions). Common ions in tap water include calcium, magnesium, sodium, and chloride. These charged particles contribute to water’s electrical conductivity and its “hardness.”
Purity and the Distillation Process
Distillation effectively removes ions because most ionic compounds are non-volatile. When water turns to steam, dissolved ions do not evaporate with water molecules. Instead, they remain in the boiling chamber as solid residues or concentrated solutions. The pure water vapor rises, leaving impurities behind. This physical separation results in water with significantly reduced ion content, often less than 1 part per million (ppm) of total dissolved solids.
Trace Impurities and Practical Considerations
While distillation yields water with very low ion content, achieving 100% purity is challenging and not maintained outside specialized conditions. Trace amounts of ions persist due to various factors. Volatile organic compounds or gases, like carbon dioxide, can vaporize with water or dissolve back into it from the air, forming weak acids that introduce ions. Slight leaching from storage containers or incomplete separation can introduce minuscule impurities. Despite these, distilled water remains exceptionally low in ion content compared to other water types.
Significance of Low Ion Content
Its low ion content makes distilled water suitable for various applications where mineral buildup or chemical interference must be avoided. It is used in car batteries to prevent corrosion, in steam irons to avoid mineral deposits, and in humidifiers. In laboratories, its purity ensures accuracy in experiments; it is also used in medical procedures and cosmetic formulations. While safe to drink, distilled water lacks beneficial minerals found in tap water, which can result in a flat taste and is not recommended as a primary source of hydration for extended periods.