Distilled water is water that has many of its impurities removed through distillation. Distillation involves boiling the water and then condensing the steam into a clean container.
History
Drinking water has been distilled from sea water since at least ca. 200 AD when the process was clearly described by Alexander of Aphrodisias. Its history predates this, as a passage in Aristotle’s Meteorologica (II.3, 358b16) refers to the distillation of water. Captain Israel Williams of the Friendship (1797) improvised a way to distill water, which he described in his journal.
Applications
In chemical and biological laboratories, as well as industry, cheaper alternatives such as deionized water are preferred over distilled water. However, if these alternatives are not sufficiently pure, distilled water is used. Where exceptionally high purity water is required, double distilled water is used.
Distilled water is also commonly used to top off lead acid batteries used in cars and trucks. The presence of other ions commonly found in tap water will cause a drastic reduction in an automobile's battery lifespan.
Distilled water is preferable to tap water for use in automotive cooling systems. The minerals and ions typically found in tap water can be corrosive to internal engine components, and can cause a more rapid depletion of the anti-corrosion additives found in most antifreeze formulations.
Distilled water is also preferable to tap water for use in model steam engine boilers and model engines of other types. Mineral build-up resulting from the use of tap water in model boilers can severely reduce the efficiency of the boilers if run for long periods. This build-up is known as boiler scale.
Using distilled water in steam irons for pressing clothes can help reduce mineral build-up and make the iron last longer. However, many iron manufacturers say that distilled water is no longer necessary in their irons.
Some people use distilled water for household aquariums because it lacks the chemicals found in tap water supplies. It is important to supplement distilled water when using it for fishkeeping;; it is too pure to sustain proper chemistry to support an aquarium ecosystem.
Distilled water is also an essential component for use in cigar humidors. Mineral build-up resulting from the
use of tap water (including bottled water) will reduce the effectiveness of the humidor.
In addition, some home brewers, who are interested in brewing a Traditional European Pilsner, will dilute their hard water with distilled water so as to mimic the soft waters of Pilsen.
Another application is to increase the density of the air to assist early airplane jet engines during takeoff in "hot and high" atmospheric conditions, as was used on the early Boeing 707.
Distilled water is also used in Constant Positive Airway Pressure (CPAP) machines. These machines are used by people with sleep apnea to help breathing throughout sleep cycles. The water evaporates and is used to humidify the air going into the users mouth. Distilled water will not leave any contaminants behind when the humidifier in the CPAP machine evaporates the water.
Equipment to Distill Water
Up until World War Two, distilling sea water to fresh water was time consuming and expensive in fuel. The saying was: "It takes one gallon of fuel to make one gallon of fresh water." Shortly before the war, Dr. R.V. Kleinschmidt developed the compression still, that became known as the Kleinschmidt Still, for extracting fresh water from sea water or contaminated water. By compressing the steam produced by boiling water, 175 gallons of fresh water could be extracted from sea water for every gallon of fuel used.
During World War Two this unit became standard on Allied ships and on trailer mounts for armies. This method was in widespread use for ships and portable water distilling units during the latter half of the century. Modern vessels now use flash-type evaporators to boil sea water, heating the water to between 70-80°C and evaporating the water in a vacuum - this is then collected as condensation before being stored.
Solar stills can be relatively simple to design and build, with very cheap materials.
[Atmospheric Water Generators also exist which make distilled water from air].
Drinking distilled water
Bottled distilled water can usually be found in supermarkets or pharmacies, and home water distillers are available as well. Water purification, such as distillation, is especially important in regions where water resources or tap water is not suitable for ingesting without boiling or chemical treatment.
Municipal water supplies almost always contain trace components at levels, which are regulated to be safe for consumption. Some other components such as trace levels of aluminium may result from the treatment process (see water purification). Fluoride and other ions are not removed through conventional water filter treatments. However, distillation eliminates most impurities.
Distilled water is also used for drinking water in arid seaside areas lacking sufficient freshwater, via desalination of seawater.
Health Concerns
The drinking of distilled water has been both advocated and discouraged for health reasons. The lack of naturally occurring minerals in distilled water has raised some concerns. The Journal of General Internal Medicine published a study on the mineral contents of different waters available in the US. The study concluded:
Drinking water sources available to North Americans may contain high levels of Ca2+, Mg2+, and Na+ and may provide clinically important portions of the recommended dietary intake of these minerals. Physicians should encourage patients to check the mineral content of their drinking water, whether tap or bottled, and choose water most appropriate for their needs.It was observed that consumption of "hard" water, or water containing dissolved solids, is associated with possible cardiovascular effects. As noted in the American Journal of Epidemiology, consumption of hard drinking water is negatively correlated with (i.e., helping to prevent) atherosclerotic heart disease.
From: http://en.wikipedia.org/wiki/Distilled_water
No comments:
Post a Comment