Definitions of Interest, Water Related
Steve Warner April 9, 2002

Acidity: An expression of the concentration of Hydrogen ions present in a solution.

Buffer: A chemical that causes a solution to resist changes in pH, or to shift the pH to a specific value.

Chloramines: Compounds formed when Chlorine and Ammonia are mixed in water. Used to kill bacteria in water, Chloramines can be inadvertently formed in Chlorinated water supplies that contain nitrogenous impurities. Can be removed by activated carbon. Chloramine level can be determined by subtracting the free Chlorine level from the total Chlorine level.

Conductivity: The electrical measurement of the water's ability to pass electric current. It is dependent on temperature and total concentration of ionized substances in solution. The lower the level of ionized substances, the lower the conductivity. Conductivity is inverse of resistivity and is measured in microsiemens/cm.

Hardness: The solution of Calcium and Magnesium as cations independent of the nature of anions present. Generally expressed in terms of Calcium Carbonate.

Micromho (microsiemens): One millionth of a Mho. Unit of measurement for conductivity (equivalent to the inverse of 1 million Ohms of resistivity). Water quality is measured by its conductivity in micromhos per centimeter. The higher the quality the lower the micromho reading.

pH: An expression of the acidity of a solution. The negative logarithm of the Hydrogen ion concentration. A pH of 1 is very acidic; pH 7 is neutral; pH 14 is very basic.

Parts per million (ppm): A measure of concentration. One part per million of water is equivalent to 1mg/liter of liquid. This is also equivalent to 0.0584 grains/U.S gallon. 17.1 ppm is equal to 1 grain per gallon.

Resistivity (of water): The electrical measurement of the water's ability to resist the flow of electric current, and is dependent on the temperature and total concentration of the ionized substances in solution. the lower the level of ionized substances, the higher the resistivity. Resistivity is the inverse of conductivity, and is measured in megaohms per centimeter.

Reverse osmosis (ro): The process by which a solution under pressure (in excess of osmotic pressure) is forced through a semi-permeable membrane from a more concentrated to a less concentrated solution.

Softener: Ion-exchange device that removes hardness from water by exchanging Calcium and Magnesium in the water for Sodium ions. The softener is regenerated with Sodium Chloride, and the Calcium and Magnesium salts are rinsed to drain.

Total dissolved solids (TDS): The total of all dissolved matter (both organic and inorganic) present in a water sample.

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