From the HBD Archive
From: roberts%studguppy@LANL.GOV (Doug Roberts @ Los Alamos National Laboratory)
Subject: More on temperature vs SG readings
Date: 1989-11-07 18:44:05 GMT

I bet you'd thought this one was dead, didn't you :-}...

I finally received on inter-library loan the reference that I had requested.
It's called Standard Density And Volumetric Tables, Circular of the Bureau of
Standards, No. 19. It's an old document: Goerge K. Burgess was the director of
the Bureau of Standards when this was published in 1924, if that means
anything to anyone. (The price of the document was 15 cents back then.)

Anyhow, the table I wanted was on page 23, Temperature corrections to readings
of Saccharometers (standard at 20C.) The heading of the table states:

[This table is calculated using the data on thermal expansion of sugar
solutions by Plato, assuming the instrument to be of Jena 16 glass. The table
should be used with caution and only for approximate results when the
temperature differs much from the standard temperature or from the temperature
of the surrounding air]

The table contains correction factors to be added to the SG reading when the
temperature is above 20C, and to be subtracted from the reading when the
temperature is below 20C. I plotted the table for a 5 percent sugar solution
for the following temperatures above 20C:

C Corr.
---------
21.0 0.05
22.0 0.10
23.0 0.16
24.0 0.22
25.0 0.28
26.0 0.34
27.0 0.41
28.0 0.47
29.0 0.55
30.0 0.62
35.0 1.01
40.0 1.45
45.0 1.94
50.0 2.48
55.0 3.07
60.0 3.72

The regression results are:

Number of observations = 16
Mean of independent variable = 33.75
Mean of dependent variable = 1.054375
Standard dev. of ind. variable = 12.47664
Standard dev. of dep. variable = 1.150913
Correlation coefficient = .9943109
Regression coefficient (slope) = 0.09172056
Standard error of coefficient = 0.00262603
t-value for coefficient = 34.92745
Regression constant (intercept) = -2.041194
Standard error of constant = 0.09413504
t-value for constant = -21.68368

Analysis of variance
Source d.f Sum of squares Mean Square F
Regression 1 19.64356 19.64356 1219.927
Residual 14 .2254314 0.01610224
Total 15 19.86899

The most pertainent figure, of course, is the Correlation coefficient of
0.9943109. This says that the relationship between temperature & SG reading
(within the specified temperature range) is pretty linear.

I didn't do a regression analysis for temperatures below 20C, but I can if
anybody's interested.

--Doug

================================================================
Douglas Roberts |
Los Alamos National Laboratory |I can resist anything
Box 1663, MS F-602 | except temptation.
Los Alamos, New Mexico 87545 | ...
(505)667-4569 |Oscar Wilde
dzzr@lanl.gov |
================================================================

Date: Tue, 7 Nov 89 09:25 EST
From: Mike Fertsch <FERTSCH@adc1.adc.ray.com>
Subject: Flavor Perception Seminar in Boston

The Boston Wort Processors Homebrew Club will be conducting a Flavor
Perception seminar on Tuesday evening, November 28. All local homebrewers who
want to learn more about defects and off-flavors in beer are welcome to
attend.

Jay Hersh (formerly from Troy Homebrewers) will be running the seminar. He
will "doctor" beers using a range of solutions and other methods to develop
standards for diacetyl, skunkiness, oxidation, phelolics, and other
off-flavors which can develop in beer. These standards are useful when
evaluating beers and trying to pinpoint defects.

Jim Koch, owner of the Sam Adams Brewery, has agreed to allow Jay and the Wort
Processors to use the tasting room at his brewery in Jamaica Plain, Boston for
this educational event. If individuals are interested, please contact Jay at
617-395-4745, or reply to me via e-mail. We need a firm headcount by 14
November. Jay estimates the cost will be $4-$5 to pay for beer and chemicals.

Mike Fertsch
fertsch@meccad.ray.com
fertsch%meccad.ray.com@a.cs.uiuc.edu
{any other path - see mailer header!}

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