Thermal Cyclers

Lawrence Washington lwashing at sunflower.bio.indiana.edu
Fri Jul 1 15:16:11 EST 1994


THE PELTIER FORCE:
	In 1834 J.C.A. Peltier found that at the junction of two dissimilar metals
carrying a small current the temperature rises or falls, depending on the
direction of the current.  For example, the temperature falls where the
positive charge is from Bi to Cu.  Quintus Icilius established in 1853 that
the rate of intake or output of heat is proportional to the magnitude of
the current,
indicating that an electromotive force resides at the Cu/Bi junction,
directed from Bi to Cu.  Electromotive forces of this type are called
Peltier emfs.

A FOOTNOTE TO HISTORY:
	At the age of eighty-three, retired from academic life and living in
Nevada, Dr. Peltier, true to his credo that one should apply ones
scientific advances in a personal manner, set out to demonstrate the
practical merits of his discovery.  His resolve set in motion  an
extraordinary series of events. He had a blacksmith build for him a full
length body suit of  semi-metallic bismuth threads wrapped with fine copper
wires, and he equipped the outfit with a dry cell battery pack.  He tested
his bimetallic suit and found that, when properly configured, it could
indeed provide a strong cooling
effect. 
        On July 4, 1860 he attired himself in the odd garb and set out to
cross Death Valley, California...on foot!  With the ambient temperature a
searing 130 F by 10:00 a.m., the venerable old man of science strode out
into the burning sand.  As reported from the scene by a local newspaper,
"Our good Professor Peltier appeared as cool as a cucumber sandwich whilst
we observers in the crowd suffered mightily beneath the cruel, hell-sent
furnace of demon Sol."  Peltier reportedly whistled a then popular Eskimo
ice fishing tune as he struck out on an intended 75 mile crossing of the
"hottest place on earth", a feat never before accomplished.
        He was not to succeed.  Tragedy struck in a most unexpected and
peculiar
way, as investigators were later to discover.  According to the coroner's
report, Dr. Peltier was in the habit of carrying several pennies with him
as good luck charms.  At the midway point in his Death Valley hike he
passed a
previously unknown hidden deposit of very rich bismuth ore.  The proximity
of the bismuth, combined with the large amount of concentrated copper in
his "lucky" pennies, created an extremely potent "Peltier" effect.  At
around noon on July 4th, in the middle of Death Valley, J.C.A. Peltier was 
found in the blazing sun, frozen into a solid block of human ice. 



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