|MadSci Network: Chemistry|
While there would be certain cases of particular reagents and tests where it would not be critical for the reagents to be prepared in distilled water, I would not presume to know which they might be, and therefore, I must answer that, "No it would not be 'safe' to substitute tap water." I would also add that using tap water might lead to a contention that any evidential conclusions drawn from the use of such reagents might be brought under suspicion by the claim that the result of the test came from impurities in the tap water. Distilled water and deionized water are not the same. In distilling the water, it is ideally separated from all other materials whether they are ionic such as salts and minerals or non-ionic such as many organic compounds (sugar, urea, alcohol, etc.)which are soluble in water. By boiling it in the distillation, the water is also sterilized. Deionized water is not boiled but passed through some material which removes only the ions which come from ionic substances. The non-ionic sustances are not removed from the water and any bacteria may be still present. So for work that must leave no doubt, deionized water would not be a good substitute for distilled water.
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