Sir William Ramsey, Lord Rayleigh, prepared nitrogen

samples by several different methods. The density of each

sample was measured as the mass of gas required to fill

a particular flask at a certain temperature and pressure.

Masses of nitrogen samples prepared by decomposition

of various nitrogen compounds were 2.29280, 2.29940,

2.29849, and 2.30054 g. Masses of "nitrogen" prepared

by removing oxygen from air in various ways were

2.31001, 2.31163, and 2.31028 g. Is the density of nitrogen

prepared from nitrogen compounds significantly different

from that prepared from air? What are the chances

of the conclusion being in error? (Study of this difference

led to the discovery of the inert gases by Lord Rayleigh).