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Fluorescein aqueous solutions, diluted from 10,000 to 1 parts-per-million in intervals of 10 fold dilution. At 1 ppm the solution is a very pale yellow. As the concentration increases the colour becomes a more vibrant yellow, then orange, with the final 10,000 ppm a deep red colour.
1 volume percent = 10,000 ppmv (i.e., parts per million by volume) with a million being defined as 10 6. Care must be taken with the concentrations expressed as ppbv to differentiate between the British billion which is 10 12 and the USA billion which is 10 9 (also referred to as the long scale and short scale billion, respectively).
Although ppmv and grains per dscf have been used in the above examples, concentrations such as ppbv (i.e., parts per billion by volume), volume percent, grams per dscm and many others may also be used. 1 percent by volume = 10,000 ppmv (i.e., parts per million by volume).
where TDS is expressed in mg/L and EC is the electrical conductivity in microsiemens per centimeter at 25 °C. The conversion factor k e varies between 0.55 and 0.8. [5] Some TDS meters use an electrical conductivity measurement to the ppm using the above formula. Regarding units, 1 ppm indicates 1 mg of dissolved solids per 1,000 g of water. [6]
As a more complex example, the concentration of nitrogen oxides (NO x) in the flue gas from an industrial furnace can be converted to a mass flow rate expressed in grams per hour (g/h) of NO x by using the following information as shown below: NO x concentration = 10 parts per million by volume = 10 ppmv = 10 volumes/10 6 volumes NO x molar mass
Moisture content measurements can be reported in multiple units, such as: parts per million, pounds of water per million standard cubic feet of gas, mass of water vapor per unit volume or mass of water vapor per unit mass of dry gas.
The U.S. Environmental Protection Agency, however, has a much higher tolerance for glysphosate in crops, allowing levels ranging from 0.1 to 310 parts per million.
The scale for APHA color goes from 0 to 500 in units of parts per million of platinum cobalt to water. Zero on this scale represents distilled water, or what is more commonly called white water. APHA standards can be used for both visual comparison and instrumental measurements.