What is the density of nitrogen at standard conditions?
One possibility for differences in measured density of an element is isotopic variation. For example, sulfur isotope abundance may vary, depending if the element is derived from soil, from sulfide minerals or as the native element from a volcanic vent. Nitrogen has two common stable isotopes: 14N and 15N. It is possible that the measurement of density varied because of natural variation.

However, it is possible the density varied because the definition of &quot;Standard Temperature and Pressure&quot; (STP) has changed over time (e.g., 101.325 kPa pre-1982, 100 kPa afterwards).

It is possible the density measurements varied because the definition of mass has changed over time.

It is possible the density measurements varied because of experimental error.


So if the discrepancies are a cause for concern in your work, check the source given for each measurement to help explain the differences.