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Encyclopedia > Double distilled water

Double distilled water (abbreviated "ddH2O" or "Bidest. water") is prepared by double distillation of water. It is used, among other things, when single distillation does not lead to sufficiently pure water for some applications in biochemistry. Laboratory distillation set-up: 1: Heat source 2: Still pot 3: Still head 4: Thermometer/Boiling point temperature 5: Condenser 6: Cooling water in 7: Cooling water out 8: Distillate/receiving flask 9: Vacuum/gas inlet 10: Still receiver 11: Heat control 12: Stirrer speed control 13: Stirrer/heat plate... Biochemistry (from Greek: , bios, life and Egyptian kēme, earth[1]) is the study of the chemical processes in living organisms. ...


Bidest water is used when pure, sterile water is essential. Whereas distilled water is enough for most chemical reactions, a molecular biologist attempting to create sterile, enzyme-free media might use bidest. water to ensure sterility. Molecular biology is the study of biology at a molecular level. ... Ribbon diagram of the enzyme TIM, surrounded by the space-filling model of the protein. ...


The theoretical pH of distilled water is 7.0. In practice, however, most distilled water will have a pH that is slightly acidic (less than 7.0) due to the presence of carbon dioxide (CO2) that is absorbed from the atmosphere. Dissolved carbon dioxide reacts slowly with water to give the bicarbonate and hydronium ions. Carbon dioxide is a chemical compound composed of two oxygen atoms covalently bonded to a single carbon atom. ... For baking soda, see Sodium bicarbonate In inorganic chemistry, a bicarbonate (IUPAC-recommended nomenclature: hydrogencarbonate) is an intermediate form in the deprotonation of carbonic acid. ... In chemistry, hydronium is the common name for the cation H3O+ derived from protonation of water. ...

CO2 + 2H2O rightleftharpoons HCO3- + H3O+

(carbonic acid, H2CO3, is only formed in strongly acid solutions). During distillation, the dissolved CO2 will be driven out of the liquid. However, during condensation the water will re-absorb the CO2 again resulting in a pH that is less than 7.0. Carbonic acid (ancient name acid of air or aerial acid) has the formula H2CO3. ...


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