Next, there's the vapor pressure. Gases with liquid/vapor phases where the liquid has a high vapor phase such as carbon dioxide (830 PSIG), will enter gas phase quickly when released. Mercery, on the other hand, has a vapor pressure of .0017 torr (not much of a vapor pressure at all, really) at 25 degrees C. In other words, it will enter the vapor phase very slowly. Other things being equal, heat will increase the vapor pressure.
The quicker the gas enters the vapor phase, the more quickly it will disperse unless there are outside factors working against it such as an inversion, the release occurring in a valley or in a confined space. A hot day, of course, will accelerate this process.
Mercury, at normal temperature and pressure, will release slowly, continually over a long period of time, so it needs to be thought of differently than most of the dense gases. There are similarities, of course, but the gasification of mercury, I think, is a little bit different animal than most.
Refrigerant gases have high molecular weights like mercury does, but they have higher vapor pressures.
So although we're used to thinking of dense gases (liquified gases shipped under their own vapor pressure) as somewhat similar, we need to give some serious thought whenwe're calculating the gasification of mercury because of its unusual combination of extraordinarily low vapor pressure and high molecular weight.
I truly think it needs its own dispersion chart.