If you could contain it, it would probably work great because of its high heat conductivity. To be honest though, there are just far too many practical problems to over come to make it worth your while considering the likely small return in temperatures. Between dealing with a low evaporation point (at what temperature the enrgy is put towards the phase change), a low heat of evaporation (the amount of energy it takes to evaporate a given amount), its high reactivity with some metals, and limited availability and its associated expense, it just isn't a worthwhile investment man.
Also, coming from a pre-med/chemistry major/researcher and to all of those people who say mercury is poisoness, you are techncally correct. In practice though, it is exceedingly
unlikely that a person would incur any
long term detrimental effects or problems as a result of using mercury in the amounts you would be working with, in the manner you would be working with it, and for the relatively short amount of time you would be exposed. Short of sitting there and sniffing the fumes for hours on end, drinking the stuff, boiling it on your stove, or having a disease or reaction which could be aggravated by the minimal exposure and small aquntities you are using there would be an unbelievably low chance of anything bad happening. For those who say organic chemists often avoid using mercury for synthesis, first of all, it isn't true, and second the main reasons mercury and mercury containing compounds are avoided as reagents are the same as any other elements or compounds are avoided, that they often have physical properties associated with them which would either hinder the yield, or make the synthesis itself impractical and/or overly expensive. It is also, by the way, not even close to the most toxic metal. That term is usually reserved for uranium, and transuraniums (plutonium, americium, etc...). Keep in mind as well that most of the biological pathways which lead to the toxicity of mercury either begin with or have numerous intermediates which are organomercuries in them and that there are just as many organometallic copounds which can be toxic in the right amounts which primarily contain metals we would normally think of as harmless. That all being said, an application where you are heating mercury, such as using it in a TIM, will create more fumes and might be a bit more unadvisable, especially if done repeatedly or exposure is over a long period of time. If there would be a way to seal it off though (then you would have to work against the intense pressure the vapor would create), this effect could and probably would be negligable. I'm not sure quite how you would go about doing that though. I'll think on it a bit.
Finally, if this thought experiment were ever to become a reality, there are plenty of standard lab procedures and and precautions you could easily take even in a residential setting, which would even further dramatically limit the possible dangers of using and handling mercury.
I hope this helps more than what some of the opthers have been saying. To everyone else: Keep in mind that, at least at this point this is simply a thought experiment. Treat it as such. I understand that there is a lot of misinformation available regarding mercury and its effects, a lot of old wives tails about it, and that you guys, especially the more senior members, are simply trying to help keep you safe (a noble and important cause if I do say so myself) but instead of putting down the idea because you think it is too dangerous (which most probably isn't true in this case anyway) try and help his speculation along and try and help him brainstorm ways that he could overcome all of the practical problems that have been mentioned.Edited by looknohands119 - 10/18/09 at 9:52pm