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In science and engineering, the parts-per notation is a set of pseudo-units to describe small values of miscellaneous dimensionless quantities, e.g. mole fraction or mass fraction. Since these fractions are quantity-per-quantity measures, they are pure numbers with no associated units of measurement. Commonly used are parts-per-million (ppm, 10 ...
Correcting concentrations for altitude. Air pollutant concentrations expressed as mass per unit volume of atmospheric air (e.g., mg/m 3, μg/m 3, etc.) at sea level will decrease with increasing altitude. The concentration decrease is directly proportional to the pressure decrease with increasing altitude.
The abundance of elements in Earth's crust is shown in tabulated form with the estimated crustal abundance for each chemical element shown as mg/kg, or parts per million (ppm) by mass (10,000 ppm = 1%).
Non-road diesel engine fuel moved to 500 ppm sulfur in 2007, and further to ULSD in 2010. Railroad locomotive and marine diesel fuel moved to 500 ppm sulfur in 2007, and changed to ULSD in 2012. There were exemptions for small refiners of non-road, locomotive and marine diesel fuel that allowed for 500 ppm diesel to remain in the system until 2014.
Median lethal dose. In toxicology, the median lethal dose, LD50 (abbreviation for " lethal dose, 50%"), LC50 (lethal concentration, 50%) or LCt50 is a toxic unit that measures the lethal dose of a given substance. [1] The value of LD 50 for a substance is the dose required to kill half the members of a tested population after a specified test ...
Prophylaxis with perchlorate-containing water at concentrations of 17 ppm, corresponding to 0.5 mg/(kg·d) intake for a person of 70 kg consuming 2 litres of water per day, was found to reduce the baseline of radioiodine uptake by 67% [10] This is equivalent to ingesting a total of just 35 mg of perchlorate ions per day. In another related ...
Chemical oxygen demand. In environmental chemistry, the chemical oxygen demand (COD) is an indicative measure of the amount of oxygen that can be consumed by reactions in a measured solution. It is commonly expressed in mass of oxygen consumed over volume of solution, which in SI units is milligrams per liter (mg / L).
Diethylamine is an organic compound with the formula (CH 3 CH 2) 2 NH. It is a secondary amine. It is a flammable, weakly alkaline liquid that is miscible with most solvents. It is a colorless liquid, but commercial samples often appear brown due to impurities. It has a strong ammonia-like odor.