Temperature relevance of the Franck-Hertz Experiment

[Azzaman]

I have to do a lab next week in which I repeat the Franck-Hertz experiment. I am reasonably sure that I understand most of what I need to do, but I'm just a little unsure on a couple of points, and would appreciate some guidance if anyone is knowledgeable with it.

The instructions say that the tube must be heated to ~180°C. I assume that this is to vapourise the mercury, and get it to a suitable pressure? Is there any other reason? I was looking online for an answer, and a lot of the pages said that the tube should under no circumstances be heated above 205°C. Is there any specific reason for this?

I may have further questions as my research continues. Any help on this would be greatly appreciated.

 

[Redbelly98]

Welcome to Physics Forums.

As you suspect, the high temperature is needed to get the mercury to a suitable pressure. For more info, scroll down to the first paragraph of the "Equipment" section here:
http://teacher.nsrl.rochester.edu/phy_labs/Franck_and_Hertz/Franck_Hertz.html

Lots of relevant google hits:
http://www.google.com/#hl=en&q=franck+hertz+mercury+temperature&aq=f&oq=&aqi=&fp=BV3slUUD4j0