TDS - the abbreviation for "total dissolved solids"
Threshhold - a very low concentration of a substance in water. The term is sometimes used to indicate the concentration which can just be detected.
Titration - an analytical process in which a standard solution in a calibrated vessel is added to a measured volume of sample until an end point, such as color change, is reached. From the volume of the sample and the volume of standard solution used, the concentration of a specific material may be calculated.
Total Acidity - the total of all forms of acidity, including mineral acidity, carbon dioxide and acid salts. Total acidity is usually determined by titration with a standard base solution to the phenolphathlein endpoint.
Total Alkalinity - the alkalinity of a water as determined by titration with standard with standard acid solution to the methyl orange endpoint(ph approx. 4.5); sometimes abbreviated as "M alkalinity" Total alkalinity includes many components, such as hydroxides, carbonates, and bicarbonates.
Total Dissolved Solids - the weight of solids per unit volume of water which are in true solution, usually determined by the evaporation of a measured volume of filtered water, and of the residue weight.
Total Hardness - the sum of all hardness constituents in a water, expressed as their equivalent concentration of calcium carbonate. Primarily due to the calcium and magnesium in solution, but may include small amounts of metals such as iron which can act like calcium and magnesium in certain reactions.
Total Solids - the weight of all solids, dissolved and suspended organic and inorganic, per unit volume of water; usually determined by the evaporation of a measured volume of water at 105c in a preweighed dish.
Turbidity - a measure of the amount of finely divided suspended matter in water, which causes the scattering and absorption of light rays.