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Recalculated

Avogadro’s number recalculated

Recalculated: this silicon sphere was used to increase the precision of a basic constant used in chemistry

Enrico Massa e Carlo Sasso /INPMRecalculated: this silicon sphere was used to increase the precision of a basic constant used in chemistryEnrico Massa e Carlo Sasso /INPM

Even if your school days are long past, you may still remember Avogadro’s number: 6 x 1023.  It is just an approximation, used to facilitate calculations during chemistry classes and exams.  According to the most recent measurement of Avogadro’s number, performed by researchers from Italy, Japan and Germany, the exact value is likely somewhere between 6.02214071 x 1023 and 6.02214093 x 1023 (Journal of Physical and Chemical Reference Data, July 2015).  To determine these values, the team led by Giovanni Mana, from the National Institute of Metrological Research in Turin, Italy, developed a new method to precisely count every atom in a one-kilogram sphere of silicon-28.  Chemists use Avogadro’s number to compare masses of different substances and keep track of their chemical reactions, using a unit of measurement called the mole.

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