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Brix to Specific Gravity for Glycol Solutions

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  • Brix to Specific Gravity for Glycol Solutions

    Is there a reference chart available to convert a brix reading to Specific Gravity when measuring an antifreeze solution. I know refractometers are manufactured with a scale specific to percent of antifreeze concentration. My refractomoters are used in my homebrewing hobby so are scaled to surcrose solutions and read in Brix only. I've found data online that relates S.G. measurements to antifreeze ratios at sample temperatures and freeze protection, but nothing for a brix reading.
    I have 2 different antifreeze solutions; with the 20 year old antifreeze out of a bulk 55gal barrel at 50/50 with RO water I read 29 Brix, at 60/40 = 35 brix. With newly purchased antifreeze I get 35 brix at 50/50 mix.

  • #2
    Re: Brix to Specific Gravity for Glycol Solutions

    Originally posted by jdieter View Post
    Is there a reference chart available to convert a brix reading to Specific Gravity when measuring an antifreeze solution. I know refractometers are manufactured with a scale specific to percent of antifreeze concentration. My refractomoters are used in my homebrewing hobby so are scaled to surcrose solutions and read in Brix only. I've found data online that relates S.G. measurements to antifreeze ratios at sample temperatures and freeze protection, but nothing for a brix reading.
    I have 2 different antifreeze solutions; with the 20 year old antifreeze out of a bulk 55gal barrel at 50/50 with RO water I read 29 Brix, at 60/40 = 35 brix. With newly purchased antifreeze I get 35 brix at 50/50 mix.
    Your refractometer measures index of refraction, it does not measure SG directly.

    The Handbook of Chemistry and Physics has an extensive table of concentrative properties of solutions. For sugar 29 Brix = 29% by weight and has an index of refraction of n = 1.3794, and 35 Brix, n = 1.3904.

    In the table for ethylene glycol, these indexes are naturally between table entries. I'll let you interpolate. The values are:
    % by weight, SG, index of refraction
    44, 1.0586, 1.3769
    48, 1.0638, 1.3811

    56, 1.0738, 1.3892
    60, 1.0784, 1.3931

    Use the index column to interpolate %by weight, then use that to interpolate the SG.

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    • #3
      Re: Brix to Specific Gravity for Glycol Solutions

      Thanks for the help JohnS exactly what I'm looking for. I'll plot the data and see how close it comes to the empirical data I've collected.

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