Limestone, chemically known as calcium carbonate (CaCO₃), has relatively low solubility in pure water.
At a standard temperature of 25 degrees Celsius (77 degrees Fahrenheit), the solubility of limestone in water is approximately 5.8 milligrams per liter (mg/L). This means that in one liter of water, only about 5.8 milligrams of limestone will dissolve.
Understanding Limestone Solubility
While often perceived as insoluble, a small amount of limestone does dissolve in water. This slight solubility is significant over geological timescales, contributing to the formation of caves and karst landscapes through dissolution by acidic rainwater (though the provided reference focuses only on pure water solubility).
Here's a summary of the solubility based on the provided information:
| Substance | Chemical Formula | Solubility in Pure Water (at 25°C) | Units |
|---|---|---|---|
| Limestone | CaCO₃ | 5.8 | mg/L |
| (Calcium Carbonate) | 0.0058 | g/L |
Why is it Considered "Relatively Insoluble"?
Compared to many common substances like salt (sodium chloride), which has a solubility of about 360,000 mg/L (360 g/L) at 25°C, limestone's solubility of 5.8 mg/L is extremely low. This vast difference is why it's accurately described as "relatively insoluble."
Practical Implications of Low Solubility
- Construction: Limestone is a durable building material precisely because it doesn't easily dissolve away when exposed to water.
- Hard Water: While low, the dissolution of limestone (and other minerals) contributes to water hardness, causing issues like scale buildup in pipes and appliances.
- Environmental Processes: Over millions of years, even this slight solubility, especially when water is slightly acidic (like rainwater absorbing atmospheric CO₂), can lead to significant geological changes like the formation of underground caverns and sinkholes.
In summary, while not zero, the solubility of limestone in pure water at typical room temperature is very low, measured in single-digit milligrams per liter.
