What is the Difference Between Carbonate and Non-Carbonate Hardness

The key difference between carbonate and non-carbonate hardness is that carbonate hardness comes from the presence of carbonate and bicarbonate anions, whereas non-carbonate hardness comes from sulfate and chloride anions.

Hardness can be described as the ability of water to precipitate soap. Both magnesium and calcium can precipitate soap. This forms a curd that results in rings in bathtubs and similar fixtures, as well as graying, yellowing, or brightness loss in washable fabrics.

1. Overview and Key Difference
2. What is Carbonate Hardness
3. What is Non-Carbonate Hardness
4. Carbonate vs Non-Carbonate Hardness in Tabular Form
5. Summary – Carbonate vs Non-Carbonate Hardness

What is Carbonate Hardness?

Carbonate hardness can be described as a measure of water hardness that is caused by the presence of carbonate and bicarbonate anions. Usually, this hardness is expressed either in degrees KH (dKH) or in parts per million calcium carbonate (ppm CaCO₃). There, one dKH equals 17.848 mg/L (ppm) CaCO₃. For example, one dKH is similar to carbonate and bicarbonate ions that can be found in a solution of approximately 17.848 milligrams of calcium carbonate per one liter of water. We can express both these measurements in mg/l CaCO₃. This means the concentration of carbonate is expressed as if calcium carbonate were the sole source of carbonate ions.

An aqueous solution consisting of 120 mg NaHCO₃ (baking soda) per liter of water contains 1.4285 mmol/l of bicarbonate. Since the molar mass of baking soda is 84.007 g/mol, it is equivalent to carbonate hardness in a solution composed of 0.71423 mmol/l of calcium carbonate. Or else, we can express it as 71.485 mg/l of calcium carbonate. However, one degree of KH is equal to 17.848 mg/L CaCO3, and the KH value for this particular solution is 4.0052 degrees.

What is Non-Carbonate Hardness?

Non-carbonate hardness can be described as the part of water’s total hardness that does not generate via carbonates but via anions of sulfate. It is the measure of magnesium and calcium salts that appear from bicarbonate and carbonate salts such as magnesium chloride and calcium sulfate. This is one of the components of total hardness along with carbonate hardness.

This term can be described as the measure of magnesium and calcium salts aside from bicarbonate and carbonate salts, including calcium sulfate and magnesium chloride. Generally, the water turns hard upon coming to contact with divalent, soluble, and metallic cations. Non-carbonate hardness will not be precipitated by boiling, and these anions can make the water more corrosive. Largely, this term is replaced by the term permanent hardness, which has the same meaning.

What is the Difference Between Carbonate and Non-Carbonate Hardness?

Carbonate hardness is a measure of water hardness that is caused by the presence of carbonate and bicarbonate anions while non-carbonate hardness is a measure of water hardness that does not generate via carbonates but via anions of sulfate. Therefore, the key difference between carbonate and non-carbonate hardness is that carbonate hardness comes from the presence of carbonate and bicarbonate anions, whereas non-carbonate hardness comes from sulfate and chloride anions. Moreover, carbonate hardness cannot be removed by boiling because it can form precipitations, while non-carbonate hardness can be removed by boiling because it does not cause precipitation.

Below is a summary of the difference between carbonate and non-carbonate hardness in tabular form for side-by-side comparison.

Summary – Carbonate vs Non-Carbonate Hardness

The hardness of water is an important factor regarding water because it can affect the chemical and physical properties of water. The key difference between carbonate and non-carbonate hardness is that carbonate hardness comes from the presence of carbonate and bicarbonate anions, whereas non-carbonate hardness comes from sulfate and chloride anions.