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Isolation of a Pure Substance

  1. Jul 4, 2007 #1
    In the crystallization process after gravity filtration is carried out, a mixture of ice and water is sometimes used as a bath instead of just ice. I know that the ice/water bath can be used to cool the filtrate to around 0 C while just crushed ice or an ice-salt bath may cool the filtrate to below 0 C. An ice/water mixture instead of pure ice is used so that the solution does not ultimately freeze?? (Are there any examples where one is preferred over another?)

    Thank you.
  2. jcsd
  3. Jul 5, 2007 #2


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    It is usually because there is better contact between the liquid and the flask in an ice/water bath. An ice bath would only contact the flask in spots.
  4. Jul 5, 2007 #3
    sometimes they add salts to the icewater bath to get it colder around -3C and the better efficency at cooling because more surface is contacted
    it depends what application is used but the freezing is not usually a problem unless you have a pure liquid with a higher freezing point. in distillation sometimes they use an isopropanol water ice bath to slow the corrosion of metal parts and it gets very cold
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