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Old 09-05-2011, 01:44 PM   #11
ajdelange
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Quote:
Originally Posted by Bierenliefhebber View Post
Similarly, it strikes me as courting error to assume - in the absence of much in the way of supporting data - that a weight of sugar dissolved in a volume of water doesn't significantly alter that solution's thermal expansion properties.
We looked at 12 °P wort in my last post. The ratio of densities of 12 °P sucrose solutions at 20 and 50 °C is 1.01096 whereas the ratio of the densities of water at those 2 temperatures is 1.01030 - pretty close i.e. 653 ppm. For 50 °P wort the ratio is 1.01247 for a difference of 2148 ppm. Getting more significant.
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Old 09-05-2011, 09:20 PM   #12
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Hm, gee, that's much closer that I'd have guessed; right at the limit of the typical homebrewer's ability to eyeball the scale on his bobbing hydrometer. I'm guessing that sugars, with all those hydroxyls hanging off the carbons, must sufficiently resemble water that it doesn't disrupt its physical properties all that much.

Well, I have to say it's been a genuine pleasure discussing matters of physical chemistry with people here who know what the heck they're talking about.

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Old 10-21-2011, 07:24 PM   #13
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After a long delay due to other projects in need of attention, plus a general propensity for sloth, I'm finally getting around to implementing temperature corrections in my program. Ajdelange, if you're still around, would agree that this is the proper parsing of your equation? I'm assuming the usual hierarchy of math operators, where "*" takes precedence over "+" and "-".
P + 0.000383644 + 0.0496253*T - 0.0000635525*P + 0.00110774T^2 + 0.00091996*T*P + 0.0000136646P^2 ?

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Old 10-21-2011, 08:06 PM   #14
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Ha ha ha ha - my eyeballs are falling out of my skull and my head hurts. You guys are too smart!

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Old 10-21-2011, 09:23 PM   #15
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Looks good to me.

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Old 10-26-2011, 09:35 PM   #16
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Having played with the above formula above a bit, I've found that T in the ASBC formula given by ajdelange is apparently not the actual temperature in °C, but rather appears to be the difference from the calibration temperature, 20° C. This is an important distinction, and one I don't think this is stated explicitly (or at least, not explicitly enough after quaffing my second 33 cl "Prince of Darkness", 9.2% a.b.v. Belgian Strong ale for the evening) anywhere in the discussion.

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Old 10-26-2011, 11:03 PM   #17
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It is an important distinction and while it is sort of obvious that this is the case it should have been stated clearly. I've edited the post in which the polynomial was introduced to make sure that people are aware of this.

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Old 10-27-2012, 11:20 AM   #18
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For those perusing this ancient thread, I'd like to add that the above-given formula has since been incorported into my brew calculator software, which is available for free, along with the source code, to anybody who would like a copy. For a couple of screenshots and testimonials, see my thread "Simple Brewing Software" under the "software" section of Homebrewtalk.

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Old 07-11-2014, 02:43 PM   #19
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ancient thread but still useful !

I need something similar to sit within my spreadsheet so I don't have to do the conversions each time. However I measure with SG not plato. I believe I can perform the conversion from Plato to SG with this formula:

SG = 1+ (plato / (258.6 – ( (plato/258.2) *227.1) ) )

but I am concerned about losing accuracy if I am doing the conversions back and forth each time - is there a version of the hydrometer correction formula for SG ?

thanks

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