What is ‘mineral water’?
Drinking water is a scarce commodity on earth – about 97.4% of the water supply is undrinkable salt water. Only 2.6% of the water on earth is ‘fresh water’ and only a fraction of those supplies is high-quality mineral water.
Mineral water is water containing minerals or other dissolved substances that alter its taste or give it therapeutic value. Salts, sulfur compounds, and gases are among the substances that can be dissolved in the water. Mineral water can often be effervescent. Mineral water can be prepared or can occur naturally.
Traditionally, mineral waters were used or consumed at their source, often referred to as taking the waters or taking the cure and such sites were referred to as spas, baths, or wells. A spa would be a place where the water was consumed and used for bathing, a bath refers to a place where the water was not generally consumed, and well refers to a place where the water was not generally used for bathing. Often an active tourist centre would grow up around a mineral water site. Such development resulted in spa towns and hydropathic hotels (often referred to as a Hydros).
In modern times, it is far more common for mineral waters to be bottled at the source and distributed for consumption. Traveling to the mineral water site for direct access to the water is now uncommon, and in many cases not possible (because of exclusive commercial ownership rights). There are over 3000 brands of mineral water commercially available worldwide.
The US FDA definition in "Standards of Identity" for Bottled Mineral Water is: This type of water contains at least 250 parts per million total dissolved solids (TDS). It comes from a source tapped at one or more bore holes or springs and originates from a geologically and physically protected underground water source. No minerals may be added to this water.
How is it different from ‘carbonated water’?
Carbonated water, also known as soda water, sparkling water, fizzy water, club soda, or seltzer water, is plain water into which carbon dioxide gas has been dissolved. The process of dissolving carbon dioxide gas is called carbonation. It results in the formation of carbonic acid (which has the chemical formula H2CO3).
In the past, soda water was produced in the home by "charging" a refillable seltzer bottle by filling it with water and then adding carbon dioxide. Club soda may be identical to plain carbonated water or it may contain a small amount of table salt, sodium citrate, sodium bicarbonate, potassium bicarbonate, potassium sulfate, or disodium phosphate, depending on the bottler. These additives are included to emulate the slightly salty taste of homemade soda water. In the UK, Soda Water is almost always made with Sodium Bicarbonate.
Today, carbonated water is made by passing pressurized carbon dioxide through water. The pressure increases the solubility and allows more carbon dioxide to dissolve than would be possible under standard atmospheric pressure. When the bottle is opened, the pressure is released, allowing the gas to come out of the solution, thus forming the characteristic bubbles.
Incidentally, carbonated water was commonly known by the name of soda water until World War II. In the 1950's new terms such as sparkling water and seltzer water began to be used. The term seltzer water is a generic trademark that comes from the German brand Selters.