I had to do an experiment to measure the latent heat of vaporization of liquid nitrogen. This was done by placing a canister of liquid nitrogen on a scale, and inserting a piece of aluminum of known mass into the canister. Knowing the initial temperature and heat capacity of aluminum, it's possible to figure out how much heat is added into the system. Then, using the recordings of the scale to figure out the rate of mass loss, it's not hard to calculate the latent heat of vaporization. Now, some of the mass loss will be due to heat entering the system from the surroundings. I tried to account for this by measuring the rate of mass loss before and after the aluminum was adding heat to the nitrogen. Here, there's an interesting effect: for about half a minute after the aluminum was at the same temperature as the liquid, the rate of mass loss was quite small but constant. Then, abruptly, the rate of mass loss increases to a value close to what it was before the experiment started. I suspect that's it's related to the fact that, at the end the period over which aluminum is dissipating heat, the rate of vaporization shoots up (because the layer of nitrogen created by the Leidenfrost effect disappears) and a noticeable decrease in mass occurs over a very short time interval. This is important because I need to estimate the rate of mass loss due to the surroundings while the piece of aluminum heating the nitrogen, and I'll get a different answer for the latent heat of vaporization if I say that the rate of mass loss is what is was right after the aluminum stops adding heat (when it was very small) or if I say that the rate of mass loss is what it was after it shoots up. So, which is it?