distilled water

Distilled water is water which has been heated to the boiling point - 212 degrees farenheit (100 C.) The evaporated water is collected; the result is distilled water. Distillation of water produces the purest water available from a single stage of processing. Distilled water may contain VOCs (volatile organic compounds), which are frequently removed with a carbon filter.

Distilling water removes nearly all impurities from water, whether biological, mineral, or chemical. In itself it does not remove 100% of VOCs like benzene and toluene whose boiling points are near that of water, but it will remove calcium, magnesium, lead, viruses, bacteria, and protozoan cysts. In fact distilling water removes metals and oxygen, which results in the "flat" taste of distilled water.

Distilled water is nonconductive but is still corrosive; water is said to be the universal solvent. However, no water is pure H₂O, as it reacts with itself, forming hydroxide and hydronium ions. Hydroxide ions are the caustic component of lye, and hydronium ions make water corrosive. Deionized water (DI water) is neither corrosive nor conductive, but it will become so over time through this process.

The health benefits or drawbacks of distilled water have long been hotly debated. The argument against drinking it claims that water will leach valuable minerals from your body, as a hypotonic environment can cause cells to take on too much water and burst, or to lose too many of the solute molecules within them. The argument for distilled water is similar, but says that the leaching process is beneficial. The reasoning is that the water will carry minerals which your cells have rejected or eliminated away from your body. These are items your body would normally eliminate through urination, and are merely being carried out of the body more rapidly than they would otherwise. Also, there are no useful minerals in tap water (with the possible exception of fluoridated water), spring water, or filtered water that you would be missing if you drank distilled water.

Water can be distilled by heating it and passing it into a cooling coil. This evaporates the water and then condenses it, turning it back into a liquid which has left behind all the heavier impurities as they do not vaporize at as low a temperature. The cooling system may have gas vents of approximately .045 inches to .065 inches in diameter to allow VOCs to escape. After it has been cooled, the water is regularly passed through a carbon filter which will ionically attract and thus filter VOCs. Electrically-powered home-scale distillers consume from .25 to about .34 kWh (kilowatt-hours) per gallon (3.79 liters) and typically are capable of producing from three to twelve gallons per day.

Water can of course be distilled using energy sources other than solar. Rainfall is the result of a distillation process, though our atmosphere is full of both natural and unnatural pollutants which render rainwater effectively undrinkable. A solar distiller can be made by building a box with a slightly sloped roof, a water inlet on the high side, and an outlet on the low side connected to a gutter, with a glass roof and black inner bottom and sides. With strong sunlight, an eight square foot solar still can produce about a gallon of water per day, over five hours of full sunlight, and more will be produced after the sun goes down as the water will still be quite warm. (For a metric representation: a 60 x 120 cm still can produce about four liters of water.) Naturally, any heat source sufficient to heat water to the boiling point can be used for distillation; not only electrical and solar, but also chemical heat (to wit: fire.)

References:

1. Senese, Fred and Kim, Rachel, Is distilled water a solution? General Chemistry Online!, 2004 (http://antoine.frostburg.edu/chem/senese/101/matter/faq/is-distilled-water-a-solution.shtml)
2. Weil, Andrew, and Pietron, Joe, Is Distilled Water Dangerous? DrWeil.com, 2004 (http://www.drweil.com/app/cda/drw_cda.html-command=TodayQA-pt=Question-questionId=21181)
3. Kocher, Jodi; Dvorak, Bruce; and Skipton, Sharon, Drinking Water Treatment: Distillation. University of Nebraska Cooperative Extension, November 2003. (http://ianrpubs.unl.edu/water/g1493.htm)
4. Derickson, Russell; Bergsrud, Fred and Bruce Seelig, Treatment Systems for Household Water Supplies: Distillation. University of Minnesota Extension Service, 1992. (http://www.extension.umn.edu/distribution/naturalresources/DD5943.html)
5. Hallaway , Joann, Drinking Water Treatment Devices: Distillers. Colorado State University, October 1993. (http://muextension.missouri.edu/explore/hesguide/houseeq/gh4863.htm)
6. Solar Water Distiller. The Institute for Appropriate Technology, 2004. (http://www.i4at.org/surv/sstill.htm)

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