I think you have mislabeled your "melting point". that should be the critical point.
Perhaps it is necessary to more carefully define terms. Unqualified, the term vapor pressure is usually taken to mean "the pressure exerted by a pure vapor/gas in equilibrium with its liquid phase." Sometimes this is extended to solids, though it is also common to use the term sublimation pressure to distinguish vapor-solid equilibrium from vapor-liquid equilibrium. Because the liquid phase only exists between the melting point and critical point, vapor pressure only has physical meaning between those two temperatures. Here's an introductory discussion of pure component phase diagrams. What we usually call "vapor pressure" is the curve connecting the triple point and the critical on these kind of phase diagrams. http://www.chemguide...phasediags.html
Someone who uses the term "vapor pressure" in reference to nitrogen at room temperature is playing rather loose and careless with the terminology. The first step in understanding what he means is to get him to either define what he means by "vapor pressure" or get him to use a better term that better describes his meaning.
Perhaps he really means "extrapolated" or "hypothetical" vapor pressure of pure nitrogen. What is the purpose for this extrapolation? What equation is wanted, because each vapor pressure equation is going to give a different extrapolation that far removed from the critical point?
Or perhaps he is really referring to "partial pressure" of nitrogen over some solution -- more of a "how soluble is nitrogen in solvent x at room temperature?". If this is what is meant, then we would be looking at Henry's law or other mixture VLE type calculation, which is much more complex than simply using the Antoine equation.
Until we know what is meant by "vapor pressure nitrogen at ambient temperatures and above," I'm not sure we can really explain how the calculations could have been performed.
Edited by MrShorty, 16 October 2013 - 12:58 PM.