Litmus "Lecanora tartarea" (Norway, Sweden), "Variolaria dealbata", "Ochrolechia parella", "Parmotrema tinctorum", and "Parmelia". Currently, the main sources are "Roccella montagnei" (Mozambique) and "Dendrographa leucophoea" (California). The main use of litmus is to test whether a solution is acidic or basic. Wet litmus paper can also be used to test for water-soluble gases that affect acidity or alkalinity; the gas dissolves in the water and the resulting solution colors the litmus paper. For instance, ammonia gas, which is alkaline, turn the red litmus paper blue. Blue litmus paper turns red under acidic conditions and red litmus paper turns blue under basic or
Alkalinity given in the unit mEq/L (milliequivalent per liter). Commercially, as in the swimming pool industry, alkalinity might also be given in parts per million of equivalent calcium carbonate (ppm CaCO). Alkalinity is sometimes incorrectly used interchangeably with basicity. For example, the addition of CO lowers the pH of a solution. This increase reduces the basicity; however, the alkalinity remains unchanged (see example below).For total alkalinity testing, N/10 HSO is used by hydrologists along with phenolphthalein indicator. In typical groundwater or seawater, the measured alkalinity is set equal to: Alkalinity can be measured by titrating a sample with a strong acid