[supercat]

Unless this bulb was illuminated at the time it broke, the mercury in it was in the form of a tiny droplet. It is not a gas or vapor until you start the bulb when it aid the formation of the plasma.

I'm pretty sure a typical fluorescent tube doesn't contain any significant quantity of gas other than mercury. Since mercury evaporates at low pressures, the tube would be filled with mercury vapor. Depending upon temperature, there may be some liquid mercury as well, but mercury in its liquid state doesn't fluoresce usefully.

[Swordmaker]

I'm pretty sure a typical fluorescent tube doesn't contain any significant quantity of gas other than mercury. Since mercury evaporates at low pressures, the tube would be filled with mercury vapor. Depending upon temperature, there may be some liquid mercury as well, but mercury in its liquid state doesn't fluoresce usefully.

The majority of the gas in fluorescent lamps is usually low pressure Argon. After first firing, it's a mixture of Argon and Mercury vapor. Some of the Mercury will condense after the power is shut off.

This guy reported finding the lamp, broken, still in its box. it may or may not have been powered up before.