Fahrenheit Scale
Steve Okonski
djl...@erols.com wrote:
>
> Anybody have an answer, or at least a theory?
>
I'm not familiar with the body temperature theory. I always assumed
Fahrenheit constructed a thermometer, labeled it with an (arbitrary)
scale, then went about measuring the temperature of various things.
Craig Burley
zud...@athena.mit.edu (Ethan Michael O'Connor) writes:
< This is from http://www.unidata.ucar.edu/staff/blynds/tmp.html#Dev
<
< Fahrenheit described how he calibrated the scale of his mercury thermometer:
<
< "placing the thermometer in a mixture of sal ammoniac or sea salt,
< ice, and water a point on the scale will be found which is denoted
< as zero. A second point is obtained if the same mixture is used
< without salt. Denote this position as 30. A third point, designated
< as 96, is obtained if the thermometer is placed in the mouth so as
< to acquire the heat of a healthy man." (D. G. Fahrenheit,Phil.
< Trans. (London) 33, 78, 1724)
<
< On this scale, Fahrenheit measured the boiling point of water to be 212.
< Later he adjusted the freezing point of water to 32 so that the interval
< between the boiling and freezing points of water could be represented by the
< more rational number 180. Temperatures measured on this scale are designated
< as degrees Fahrenheit.
He must have had magical powers to be able to adjust the freezing point
of water without changing the 0 and 212 points! Wonder what the
freezing point was *before* he made that adjustment? ;)
< In 1745, Carolus Linnaeus of Upsula, Sweden, described a scale in which the
< freezing point of water was zero, and the boiling point 100, making it a
< centigrade (one hundred steps) scale. Anders Celsius (1701-1744) used the
< reverse scale in which 100 represented the freezing point and zero the
< boiling point of water, still, of course, with 100 degrees between the two
< defining points.
Huh, so Celsius was really a "backwards" scale, with lower temperatures
being denoted by higher *values*? Wow!
< In 1948 use of the Centigrade scale was dropped in favor of a new scale using
< degrees Celsius (° C). The Celsius scale is defined by the following two
< items that will be discussed later in this essay:
<
< (i) the triple point of water is defined to be 0.01 C
< (ii) a degree Celsius equals the same temperature change as a degree on the
< ideal-gas scale.
<
< On the Celsius scale the boiling point of water at standard atmospheric
< pressure is 99.975 C in contrast to the 100 degrees defined by the Centigrade
< scale."
Hmm. Well, *I'm* confused, but thanks for the URL, someday I might
look it up.
--
"Practice random senselessness and act kind of beautiful."
James Craig Burley, Software Craftsperson bur...@gnu.ai.mit.edu
dba...@mindspring.com
I remember reading about his development (15 years ago) that zero was
the point at which salt water would freeze.
Erick R. Williams
Found this on the 'net:
It was in 1724 that Gabriel Fahrenheit, an instrument maker of Däanzig
and Amsterdam, used mercury as the thermometric
liquid. Mercury's thermal expansion is large and fairly uniform, it does
not adhere to the glass, and it remains a liquid over a
wide range of temperatures. Its silvery appearance makes it easy to
read.
Fahrenheit described how he calibrated the scale of his mercury
thermometer:
"placing the thermometer in a mixture of sal ammoniac or sea salt,
ice, and water a point on the scale will be
found which is denoted as zero. A second point is obtained if the
same mixture is used without salt. Denote this
position as 30. A third point, designated as 96, is obtained if the
thermometer is placed in the mouth so as to
acquire the heat of a healthy man." (D. G. Fahrenheit,Phil. Trans.
(London) 33, 78, 1724)
On this scale, Fahrenheit measured the boiling point of water to be 212.
Later he adjusted the freezing point of water to 32 so
that the interval between the boiling and freezing points of water could
be represented by the more rational number 180.
Temperatures measured on this scale are designated as degrees Fahrenheit
(° F).