Strontium unit Strontium unit The strontium unit is a unit used to measure the amount of radioactivity from strontium-90, a radionuclide found in nuclear fallout, in a subject's body. Since the human body absorbs strontium as if it were calcium, incorporating it into the skeleton, its presence is very common. One strontium unit is equal to one picocurie from strontium-90 per gram of calcium (37 becquerels per kilogram) in the subject's skeleton. The United States National Academy of Sciences holds that the maximum safe measure of strontium-90 in a person is one hundred strontium units (3700 Bq/kg). The average American is estimated
Mole (unit) 1%. The name "mole" is an 1897 translation of the German unit "Mol", coined by the chemist Wilhelm Ostwald in 1894 from the German word "Molekül" (molecule). However, the related concept of equivalent mass had been in use at least a century earlier. The mole was made the seventh SI base unit in 1971 by the 14th CGPM. At the 26th CGPM the definition of the mole was changed from a number derived from a weight (the number of atoms in 12 grams of carbon-12, C) to directly being equal to Avogadro's constant. Since its adoption into the International System