when was it first measured?
1865.
Avogadro constant
The value of Avogadro's number (not yet known by that name) was first obtained indirectly by Josef Loschmidt in 1865, by estimating the number of particles in a given volume of gas.
all valid methods for calculating avogadro’s number would indicate a constant value UNANSWERABLE what is this constant? It is the proportionality factor that relates the number of constituent particles in a sample with the amount of substance in that sample. whom is it named after? The Italian scientist Amedeo Avogadro.
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Avogadro constant [SEP] First measurements
The value of Avogadro's number (not yet known by that name) was first obtained indirectly by Josef Loschmidt in 1865, by estimating the number of particles in a given volume of gas. This value, the number density "n" of particles in an ideal gas, is now called the Loschmidt constant in his honor, and is related to the Avogadro constant, "N", by where "p" is the pressure, "R" is the gas constant, and "T" is the absolute temperature. Because of this work, the symbol "L" is sometimes used for the Avogadro constant, and, in German literature, that name may be used for both constants, distinguished only by the units of measurement.