The pH scale, which runs from 0 to 14, measures how acidic or basic a water solution is. Water with a neutral pH of 7 is neither acidic nor alkaline. Alkaline water has a pH value greater than 7, typically falling between 8 and 9.5 for commercial products. This higher pH means the water has a lower concentration of positively charged hydrogen ions (\(H^+\)) and a greater concentration of negatively charged hydroxide ions (\(OH^-\)). Interest in alkaline water for its perceived health benefits has led to various production methods.
Natural Sources of Alkalinity
Water becomes naturally alkaline through an extensive geological filtration process over long periods. As groundwater flows through deep underground springs or aquifers, it interacts with mineral-rich rocks and soil. This contact dissolves alkaline minerals from the surrounding geological structures, which are then carried into the water.
The minerals responsible for raising the water’s pH are calcium, magnesium, and potassium, often present as bicarbonates and carbonates. For example, water flowing over limestone or chalk (calcium carbonate) dissolves these compounds, increasing its alkalinity. This natural infusion of dissolved minerals gives the water its characteristic high pH and is the source of many commercially bottled natural alkaline waters.
The Process of Water Ionization
Water ionization is an artificial process that uses electricity to separate water into alkaline and acidic streams. This method, known as electrolysis, is performed by a water ionizer connected directly to a water supply. The process begins after the source water is filtered to remove contaminants.
The filtered water flows into a specialized chamber containing platinum-coated titanium plates that act as electrodes. A direct electrical current is passed through these plates, initiating electrolysis. Water molecules dissociate into \(H^+\) and \(OH^-\) ions, and the electric field pulls these ions toward the oppositely charged electrodes.
A semi-permeable membrane separates the chamber, preventing the resulting solutions from mixing. Positively charged ions (like calcium and magnesium) are drawn toward the negatively charged electrode (cathode). Here, the concentration of \(H^+\) ions decreases, creating the alkaline stream collected for drinking. Negatively charged ions are drawn to the positive electrode (anode), resulting in an acidic stream that is typically discarded or used for other purposes.
Achieving Alkalinity with Additives
A simpler, non-electrolytic method for creating alkaline water involves adding chemical compounds or mineral concentrates. Commercial options include pH drops, which are liquid concentrates composed of highly alkaline minerals. These drops often contain concentrated solutions of compounds like potassium carbonate or sodium hydroxide.
When added to regular water, these concentrated mineral solutions chemically react to raise the overall pH of the mixture. Only a few drops are needed to significantly change the water’s pH level.
A common and inexpensive home method uses food-grade sodium bicarbonate, which is ordinary baking soda. Sodium bicarbonate acts as a buffering agent, helping the water resist changes in pH. By stirring a small amount (about 1/8 teaspoon per eight ounces of water), the solution becomes alkaline, typically reaching a pH of around 8.5.