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Re: 95% boiling temp. as a azeotropic mixture

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  • abbababbaccc
    Hmm, what you controll in a normal still is the reflux ratio. The temperature at the top indicates the composition of vapors there. This can be changed by
    Message 1 of 5 , Oct 1, 2006
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      Hmm, what you controll in a normal still is the reflux ratio. The
      temperature at the top indicates the composition of vapors there.
      This can be changed by changing reflux ratio and letting the column
      adapt to new RR. 95.6% alcohol has 78.2C as you mentioned, so if you
      want to produce that percentage you should "steer" your column using
      that temperature as the purity indicator.

      Cheers, Riku

      --- In Distillers@yahoogroups.com, Robert Thomas <whosbrewing@...>
      wrote:
      >
      > Whatever is stable. Remember, you can't control the head temp: the
      > mixture does that. The best you can do is have the lowest stable
      > temperature that can be produced from a healthy reflux.
      >
      > not only that but accurately measuring the 0.15 degC difference is
      > pretty much impossible on normal setups.
      >
      > cheers
      > Rob.
      >
      >
      > --- kirtgk <kirtgk@...> wrote:
      >
      > > snip<Absolute Ethanol
      > > Whatever method of preparation is used, the ethanol is initially
      > > obtained in admixture with water. The ethanol is then extracted
      from
      > > this solution by fractional distillation.
      > >
      > > Although the boiling point of ethanol, 78.3 degC, is significantly
      > > lower than the boiling point of water, 100 degC, these material
      > > cannot
      > > be separated completely by distillation. Instead, an azeotropic
      > > mixture (i.e. a mixture of 95% ethanol and 5% water) is obtained,
      and
      > > the boiling point of the azeotrope is 78.15oC.> snip
      > >
      > > what is the best temp to run the still head at????
      > >
      > > kirtgk
      > >
      > >
      > >
      > >
      >
      >
      > Cheers,
      > Rob.
      >
      > __________________________________________________
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      > Tired of spam? Yahoo! Mail has the best spam protection around
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    • Robert Thomas
      Isn t that what I said, Riku? If, for simplicity, we assume all heads have been removed, then the lowest stable temperature (ie stable even though you are
      Message 2 of 5 , Oct 1, 2006
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        Isn't that what I said, Riku?
        If, for simplicity, we assume all heads have been removed, then the
        lowest stable temperature (ie stable even though you are removing
        product, not drifting upwards) is the azeotrope. Providing you have a
        sufficient RR the head temp will sit at this temp until much/most of
        the ethanol in the still is depleted (providing you adjust the RR =
        takeoff speed to reflect the decreasing volumes of ethanol in the
        vapours).
        Whether your thermometer reads 78.2 or even 79.5 is not as important,
        because the accuracy, placement and even response time of the
        thermometer can be less than optimal.

        I get what you mean about "steering" the head temp, but it does suggest
        that you can make the head temp what you want and expect the product
        purity to reflect that. Surely what you are really doing is maintaining
        the lowest feasible temperature for a particular heat input, by
        adjusting the reflux ratio. after all, heads have to come off before
        ethanol, which has to be before tails: it is no coincidence that this
        is in order of boiling point ;)

        Perhaps i'm just being pedantic on this sunny Sunday morning,
        good health,
        Rob.


        --- abbababbaccc <abbababbaccc@...> wrote:

        > Hmm, what you controll in a normal still is the reflux ratio. The
        > temperature at the top indicates the composition of vapors there.
        > This can be changed by changing reflux ratio and letting the column
        > adapt to new RR. 95.6% alcohol has 78.2C as you mentioned, so if you
        > want to produce that percentage you should "steer" your column using
        > that temperature as the purity indicator.
        >
        > Cheers, Riku
        >
        > --- In Distillers@yahoogroups.com, Robert Thomas <whosbrewing@...>
        > wrote:
        > >
        > > Whatever is stable. Remember, you can't control the head temp: the
        > > mixture does that. The best you can do is have the lowest stable
        > > temperature that can be produced from a healthy reflux.
        > >
        > > not only that but accurately measuring the 0.15 degC difference is
        > > pretty much impossible on normal setups.
        > >
        > > cheers
        > > Rob.
        > >
        > >
        > > --- kirtgk <kirtgk@...> wrote:
        > >
        > > > snip<Absolute Ethanol
        > > > Whatever method of preparation is used, the ethanol is initially
        > > > obtained in admixture with water. The ethanol is then extracted
        > from
        > > > this solution by fractional distillation.
        > > >
        > > > Although the boiling point of ethanol, 78.3 degC, is
        > significantly
        > > > lower than the boiling point of water, 100 degC, these material
        > > > cannot
        > > > be separated completely by distillation. Instead, an azeotropic
        > > > mixture (i.e. a mixture of 95% ethanol and 5% water) is obtained,
        >
        > and
        > > > the boiling point of the azeotrope is 78.15oC.> snip
        > > >
        > > > what is the best temp to run the still head at????
        > > >
        > > > kirtgk
        > > >
        > > >
        > > >
        > > >
        > >
        > >
        > > Cheers,
        > > Rob.
        > >
        > > __________________________________________________
        > > Do You Yahoo!?
        > > Tired of spam? Yahoo! Mail has the best spam protection around
        > > http://mail.yahoo.com
        > >
        >
        >
        >
        >
        >
        >


        Cheers,
        Rob.

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      • kirtgk
        in my still i have a reflux condensor. with this turned up i can get full reflux and also bring the head temp down if i wish to. i can vary it down to around
        Message 3 of 5 , Oct 1, 2006
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          in my still i have a reflux condensor. with this turned up i can get
          full reflux and also bring the head temp down if i wish to. i can vary
          it down to around 130F and keep the burner on. i use propane and on
          final product collection i run the burner at 5000 btu.(half of its
          capacity)



          --- In Distillers@yahoogroups.com, Robert Thomas <whosbrewing@...> wrote:
          >
          > Whatever is stable. Remember, you can't control the head temp: the
          > mixture does that. The best you can do is have the lowest stable
          > temperature that can be produced from a healthy reflux.
          >
          > not only that but accurately measuring the 0.15 degC difference is
          > pretty much impossible on normal setups.
          >
          > cheers
          > Rob.
          >
          >
          > --- kirtgk <kirtgk@...> wrote:
          >
          > > snip<Absolute Ethanol
          > > Whatever method of preparation is used, the ethanol is initially
          > > obtained in admixture with water. The ethanol is then extracted from
          > > this solution by fractional distillation.
          > >
          > > Although the boiling point of ethanol, 78.3 degC, is significantly
          > > lower than the boiling point of water, 100 degC, these material
          > > cannot
          > > be separated completely by distillation. Instead, an azeotropic
          > > mixture (i.e. a mixture of 95% ethanol and 5% water) is obtained, and
          > > the boiling point of the azeotrope is 78.15oC.> snip
          > >
          > > what is the best temp to run the still head at????
          > >
          > > kirtgk
          > >
          > >
          > >
          > >
          >
          >
          > Cheers,
          > Rob.
          >
          > __________________________________________________
          > Do You Yahoo!?
          > Tired of spam? Yahoo! Mail has the best spam protection around
          > http://mail.yahoo.com
          >
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