"Athel Cornish-Bowden" wrote in message
news:afkgje...@mid.individual.net...
> On 2012-11-03 11:34:10 +0000, Don Phillipson said:
> > This is valuable evidence how often people get muddled when
> > measuring heat numerically. There is no mystery how Fahrenheit
> > first calibrated his scale (from 0 = freezing point of salt brine to 0
> 100 Shirley? (OK, I realize that it was a thinko.)
> =
> > normal blood heat), or Celsius (differently).
Actually, it was 96 degrees Fahrenheit, not 100. The melting point of water
was 32 and the human body was 96, so that gave him 64 degrees between the
two, which could be marked off by bisecting the intervals.
http://www.sizes.com/units/temperature_Fahrenheit.htm has a translation of
the source material:
" Yet before I undertake a review of these experiments it will be necessary
to say a few words about the thermometers that I have built, and the
division of the scale they use, and in addition the method of producing a
vacuum I have used. I make two particular types of thermometer, one of which
is filled with alcohol and the other with mercury. Their length varies in
accordance with the use to which they are put. Yet all use the same scale,
and their differences relate only to their fixed limits. The scale of those
thermometers that are used only for observations on the weather begins with
zero and ends on the 96th degree. The division of the scale depends on three
fixed points, which can be determined in the following manner. The first is
found in the uncalibrated part or the beginning of the scale, and is
determined by a mixture of ice, water and ammonium chloride or even sea
salt. If the thermometer is placed in this mixture, its liquid descends as
far as the degree that is marked with a zero. This experiment succeeds
better in winter than in summer. The second point is obtained if water and
ice are mixed without the aforementioned salts. When the thermometer is
placed in this mixture, its liquid reaches the 32nd degree. I call this
‘freezing point’. For still waters are already covered with a very thin
layer of ice when the liquid of the thermometer touches this point in
winter. The third point is situated at the 96th degree. Alcohol expands up
to this point when it is held in the mouth or under the armpit of a living
man in good health until it has completely acquired his body heat. But if
the temperature of a man suffering from fever or some other heating disease
is to be investigated, another thermometer must be used, with a scale
extended to the 128th or 132nd degree. I have not yet discovered by
experiment whether these degrees are sufficient for the most intense heat of
some fever, but it is scarcely credible that the heat of any fever should
exceed the degrees I have described. When a thermometer is being used to
investigate the temperature of boiling liquids, it too starts from zero and
contains 600 degrees, for around this point mercury itself (with which the
thermometer is filled) begins to boil. "
--
Guy Barry