Thermometer fluid is separated, defective? I bought a thermometer from Cole-Parmer having kerosene as the fluid, and the fluid is broken up. The fluid in the bottom part goes up to about 10 °C even though it is 20 °C in the room, then there is a gap followed by fluid between 23 °C and 25 °C, then there is no fluid going all the way to the top where there is another small stretch of fluid. There is a short black rubber sleeve on the top of thermometer.

Does this mean the thermometer is defective or am I using it incorrectly, not “calibrating” it or something?
No, it is not defective, just slightly damaged, possibly from shipping. You should call customer service at Cole-Palmer and see if they will replace (or repair) the thermometer.

If not, there are 2 ways to fix it. I haven't tried either one, so I don't know how well they work.

If there is a bulb at the top and the thermometer is low range (under 150°C), then you would heat the thermometer in an upright position until all the bubbles are pushed up into the bulb. 

The other method is to cool the thermometer down until all the liquid is in the bottom bulb. The second method may not work if the liquid freezes before all the liquid has moved into the bulb.