[ QUOTE ]
Isis said:
Correct me someone if I'm wrong but I believe distilled water is the condensation that builds up and drips when water is boiled with a lid on. It isn't the boiled water itself.
[/ QUOTE ]
Isis, you're right; it isn't just the boiled water. Usually when water is distilled, the steam (which is 100% pure water) flows through a tube into a clean section of the apparatus where it condenses back into water. By moving the steam to a new section, you separate it from other impurities that do not become vapor at 100 degrees celsius (water's boiling point). If you could find a way to collect the steam and then allow it to condense away from the original water, then you might get distilled water.
Here's a diagram showing simple distillation.
[ QUOTE ]
Simple distillation is designed to evaporate a volatile liquid from a solution of non-volatile substances; the vapour is then condensed in the water condenser and collected in the receiver.
The apparatus consists of a round-bottomed distilling flask bearing a stillhead connected to a water condenser (Liebig condenser). This is attached via a vented delivery bend to the receiver, also a round-bottomed flask. The stillhead has a thermometer adapter with a thermometer.
Notes:
<ul type="square">- the bulb of the thermometer is opposite the exit to the condenser. You want the temperature of the exit vapours since it is these that will condense.
- the delivery bend is vented so that when the apparatus is heated the joints aren't pushed apart by expanding gas. Never draw a closed apparatus.
- water goes in at the bottom of the condenser jacket and out at the top.
- note the structure of the condenser - the water jacket is separate from the tube down the middle! [/list]
[/ QUOTE ]
Source: http://www.rod.beavon.clara.net/distil.htm
Notice a thermometer is used to measure the temperature of the vapor to make sure it's at 100 degrees celsius. I guess you'd not start running the water needed to cool the vapor down through the condenser (nor start collecting any liquid) until the thermometer showed that the temperature of the vapor was 100 degrees, indicating it was pure water vapor. Any impurities in water will turn to vapor at a lower temperature. So that's why you would need to measure the temperature to make sure it was 100% water before you start cooling it down or collecting it.
OK, I'll crawl back to the hole from whence I came before my chemistry teacher from high school finds out I've been fronting like I ever paid attention in class.