<P> Distilled water is water that has had many of its impurities removed through distillation . Distillation involves boiling the water and then condensing the steam into a clean container . </P> <P> Drinking water has been distilled from sea water since at least about AD 200, 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 . </P> <P> In chemical and biological laboratories, as well as in industry, cheaper alternatives such as deionized water are preferred to distilled water . But if these alternatives are not pure enough, distilled water is used . If exceptionally high purity water is required, double distilled water is used . </P>

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