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The History of Temperature
and Thermometry |
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The realization that some things are hotter
than others and that some are colder must have long preceded
the concept of temperature in the history of human. Although
ancient cooks and bakers, smelters and smiths, potters and ceramists
don't know the distinction between heat and temperature, their
works are involved in temperature. We can tell a toddler some
things are too hot and others are too cold even we don't know
the temperature.
Temperature may be said to derive from the recognition of the
need to define these differences more precisely than by the
positive, comparative and superlative of adjective hot and cold.
Aristotle postulated his four qualities the hot, the cold, the
moist, and the dry, set up a conception which endured for about
two thousand years.
The ideas of Aristotle were adopted by Galen(A.D. 130-200),who
was the first man to describe the heat and cold by a number
about fifteen hundred years ago. And the word temperature originated
from temper, after Galen determined the "complexion"
of a person by the proportion in which above four qualities
were tempered. [1].He gave the earliest notion of a standard
of temperature, although the temperature meant the tempering
of the qualities in a substance until the eighteenth century.
The temperature had a precise physical meaning today, temperature
is the degree of sensible heat of a body. In other words, temperature
is the hotness of a body - like the density of liquid or the
brightness of a lamp.(Even more so, for today intensity of sound
and light flux are expressed in CGS units).Unlike mass or length
which are both extensive and additive, temperature is intensive.
Temperature is an intensive and dimensionless magnitude-one
of the few purely such in all natural phenomena. [2] In other
definition, temperature can be considered to be the level of
thermal energy. It is analogous to voltage as the level of electrical
energy, or to elevation as the level of mechanical potential
energy. Temperature is the driving force for heat flow, just
as voltage is the driving force for fluid flow.[3]
The concept of temperature has been the most difficult of the
common properties of matter to define clearly. It is helpful
to review the historical development of temperature measurement
because only after crude methods of temperature measurement
were developed could the concept of temperature really be defined.
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The History of Thermometry |
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The concept of temperature, as the scientific
principles on which temperature measurement is based, evolved
as a part of the development of the science.
The instrument by which the temperature of bodies is registered
is called a thermometer or measurer of warmth, and the method
of constructing and using thermometers may be called thermometry.[4]The
history of thermometry was a part of history of science. The
history will give us insights regarding the meaning of temperature
and its measurement units, and will give us some background
regards other concerns which need to be met.
The ancient Greek knew the expansion of air by heat long time
ago. The earliest writings concerned that phenomena were the
Works of Philo of Byzantium(II Cent. B.C.) and Heron of Alexandria.
Due to the intercourse of culture, their works were translated
into Arabic and Latin version.
And della Porta was an important disseminator, whose chief work
Magia Naturalis( Natural Magic,1558,1589) not only included
many classical antiquity and tradition, but also originated
some experiments and contrivances. A simple air-thermoscope
was described, which traps air in a bulb so that the air expands
or contracts in response to a temperature increase or decrease,
it moves a liquid column in a long tube (Fig. 1.1). Thermoscope
is the not a thermometer but is its predecessor. the logical
distinction between the two is that the thermometer possesses
a scale, while a thermoscope does not.
The history of knowledge decided the earliest thermometer was
the air thermometer after the air-thermoscope appeared. There
were four inventors of thermometer at the first few years of
the seventeenth century, they were Galileo, Sanitorio, Fludd
and Drebbel.
It was said that Galileo was the first inventor of thermometer,
but there was no work or document survived in which Galileo
claimed his invention or made any question about priority, and
he certainly gave little or no attention to the use and development
of thermometer.
By modern standard the first physiologist Santorio Santorii
(Sanctorius) of Padua would be regarded as the discoverer of
the thermometer, for he published the earliest account of it
in Part III of his commentaria in artem Medicinalem Galenis
(Venice,1612),of which the Imprimatur is dated 1611.Santorio
claimed he had adapted thermometer (Fig.1.2) from Heron. He
used the instrument to estimate the heat of a patient's heart
by measuring the heat of the expired air. His method of measurement
was quite different from that of modern physicians. He measured
the rate of change of the temperature of the thermometer by
observing the distance through which the liquid fell during
ten beats of a pulsilogium, a small pendulum. The result depended
not only on the patient's temperature, but on the rapidity of
his peripheral circulation. That was a fast indictor of fever
because the ordinary thermometer took much longer to attain
the temperature of normal person than that of a fever patient. |
Fig.1.1 the first published figure
of
thermoscope(published 1620),
Inventor was Santorio.[1] |
Fig.1.2 The thermometer of Sanctorius
(1622,op. cit.,col. 22),
with pulsailogium on left. |
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Englishman Robert Fludd(1574-1651) also
was regarded as one independent inventor of thermometer, he
may have modified Philo's apparatus into the weather-glass but
did not do so until some period between 1617 and 1626. Philo
described an experiment to demonstrate the expansion of air
by heat ,in which a tube from a hollow sphere was extended over
a jug of water. If the sphere was placed in the sun, bubbles
were released as air expanded out of the sphere. When moved
to the shade, water rose in the tube as air in the sphere contracted(like
left side of Fig. 1.3 ,but no scale on the tube). Fludd's contribution
was to set the scale on the tube, and place the sphere vertically
above the jug, converting ancient Philo's air-thermoscope to
an air-thermometer.
The fourth inventor of thermometer was Drebbel, He made a two-bulbed
J-shaped thermometer at any date between 1598 and 1622. (Fig.1.4),
although Drebbel planned to construct a perpetuum mobile by
the contraction or expansion of an enclosed air at the beginning. |
Fig.1.3 The illustration of thermometer
in the
Philosophia Moysaica(by Fludd,1638,p.2) |
Fig.1.4 Drebbel Thermometers from
Leurechon's Recreations
Mathematiques(facing p.90) Enlarged from 1626 edition. |
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One fault of the air-thermometer was
they also responded to the change in atmospheric pressure. The
effect was not known originally, as there was no concept of
an atmospheric pressure. Two other problems, the lack of portability
and evaporation of water, led to the development of sealed thermometers,
namely the liquid-in-glass thermometer.
The sealed liquid-in-glass thermometer was invented by Ferdinand
II,Grand Duck of Tuscany, in about 1654[note,1641 on "Temperature"
by T.J Quinn], it used the thermal dilation of a liquid instead
of air to sense temperature changes.[3]The volume of most substances
increases continuously as the temperature rises, the liquid
dilation was much less than that of air, the first liquid in
the glass was spirits of wine, and the end of the tube was sealed
with a flame(Fig.1.5). But this kind of thermometer met the
problem of comparisons, which thermometer was the correct? Since
there was no calibration some time until the people knew a fixed
reference temperature in physical situation. Every thermometer
craftsman produced a unique instrument. One can only make comparisons
of temperature by using the same instrument, or perhaps with
a nearly identical instrument made by the same craftsman.
One of the earliest attempts at calibration and standardization
between thermometers was made in October 1663 in London. The
members of Royal Society of London agreed to use one of several
thermometers made by Robert Hooke as the standard so that the
reading of others could be adjusted to it. Thus the reading
in one laboratory could compare a temperature to reading in
another laboratory through the standard correction.
The development of stable Fahrenheit thermometers was a watershed
point in the development of thermometry. The methods of making
scale were in confusion at that time, because the craftsman
in different countries used different calibration points, there
were 18 scales up to 1841. Daniel Gabriel Fahrenheit, a Danzig
instrument maker learned the calibration of thermometer from
Ole Romer, a Danish astronomer. Between 1708 and 1724, Fahrenheit
begun producing thermometers, first with Romer's scale, then
with a modified Romer scale, and finally with the Fahrenheit's
scale, used today. Fahrenheit improved the precision of thermometer
greatly after he made the bulb of thermometer a cylinder rather
than a globe, substituted mercury for spirits because mercury
had a more nearly linear thermal expansion with temperature.
Many of his procedures for producing quality thermometers appeared
to be trade secrets, it was fairly certain that he used the
melting point of the mixture of sea salt, ice and water, the
armpit temperature of a healthy man as calibration points(Fig.1.6)).When
this scale was adopted by Great Britain, the temperature of
212?was established as the boiling point; this temperature and
the ice point was used as the two fixed calibration points.
Following Fahrenheit's work, many scientists developed the practical
scales based upon arbitrary fixed points, such as Celsius,,Daniell
,Becquerel.
In about 1740, Anders Celsius in Uppsala,Sweden, prosposed his
centigrade scale, he had the boiling point of water at 0?, and
the freezing point of water at 100?.The word "centigrade"
means a scale that is divided into 100 parts. It's not clear
that where and by whom the centigrade scale was invented, the
centigrade scale means the "Celsius" scale now. Some
believed that Carl Von Linne probably had suggested to Celsius
the possibility of dividing the space between the ice point
and steam point into 100 parts, Linnaeus inverted the scale
to the scale we use today. It was in 1948 that the name of that
scale has been the "Celsius" scale. |
Fig1.5 Liquid-in-glass thermometer
of
the Accademia del Cimento. |
Fig1.6 Fahrenheit
thermometer in1850s. |
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Daniell had invented a pyrometer in 1825,when
the future Lord Kelvin was a year old. Becquerel had used a
platinum-vs-palladium thermocouple in 1826.
The branch of thermometry initiated by Fahrenheit led ,via mercury
thermometer, platinum resistance thermometer and platinum-vs-palladium
thermocouple toward the end of the nineteenth century[5]. We'll
see the culminating result of practical thermometry the International
Temperature Scale of 1990(ITS-90) in the Chapter 2.
But the practical thermometry cannot tell the precise meaning
of temperature, and the size of the degree, the unit for measuring
temperature, was completely arbitrary. The two primary degree
units in use today were based on the original centigrade and
Fahrenheit scales. There are 180 degrees between the ice point
and the boiling point on the Fahrenheit scale, and 100 degrees
for the same interval on the centigrade scale. So the Fahrenheit
degree is smaller and 1 degree centigrade(now Celsius) equals
1.8 degrees Fahrenheit, so the practical temperature scale depends
on the properties of some bodies
Another branch of thermometry is the gas thermometry and thermodynamic
thermometry.
Before Fahrenheit thermometer appeared, Robert Boyle reported
on his study of air trapped in a U tube in 1660,he found that
the volume at constant pressure was a function of temperature.
While Fahrenheit studies his liquid-in-glass thermometer, the
French scientist Amontons developed the constant volume gas
thermometer. He used air as the thermometric medium, and concluded
that the lowest temperature which could exist would correspond
to a zero gas pressure. This must have been the first step on
the way to an understanding of the concept of temperature. According
to Amontons we could define the temperature as being simply
proportional to the pressure of a gas, and thus we would need
only one fixed point to define a scale[5]. But the new temperature
scale didn't appear at that time, maybe because of the cumbersome
operation of gas thermometer. Jacques-Alexandre Charles studied
the phenomena again in 1787.Jaspeh L. Gay-Lussac extended Charle's
work, all his gases-air, oxygen, nitrogen, hydrogen, and carbon
dioxide-expanded the same amount when heated from the ice point
to the boiling point. The result showed that at constant pressure,
and the =1/267 (degree)-1 is the mean volumetric coefficient
of thermal expansion. In 1847,Victor Regnault obtained a better
value of 1/273. Later experiments revealed that all gas had
a very slightly different thermal coefficients, however all
were found to approach a common value 1/273.15degC as the pressure
approached zero. The gases that obey the temperature-volume
relationship exactly at constant pressure (and the pressure-volume
relationship exactly at constant volume) were defined the perfect
(or "ideal" or "simple") gas. In fact,all
gases at extremely low pressure approach perfect gas behavior.
The volume of the perfect gas in the gas thermometer will approach
zero as t= -273.15 because at constant pressure. We can establish
a new zero of temperature at the ice point -273.15 , namely
the absolute zero degree. And the perfect gas temperature scale
T= t+273.16 was defined in 1954. The gas thermometer is now
rarely used directly in practical work for the measurement of
temperatures, owing to the complications that would be involved
consequently to realize the gas scale it is necessary to transfer
the scale to auxiliary standards, that is the above empirical
temperature scale.[6]
The precise meaning of temperature came after the Kelvin's thermodynamic
temperature appeared. In 1824, Carnot had laid down his principle
of reversibility with regard to "quantity of heat"
in an ideal "body" that "undergoes changes"
and in 1845(after 30 years of experiments)Joule demonstrated
mechanical equivalence. Heat now became an engineering "quantity",
measurable in foot-pounds. But what was temperature? The explanation
seems so near, but look here " the higher the temperature
the greater the quantity of heat in Carnot's "body".
If we can't ever know what temperature is ,can we at least establish
its real relation to heat independently of the actual behavior
of mercury, or of a gas and yet in such a way that we can make
the thermometers that agree with one another?[1] By the first
law and the second law of thermodynamic law, it is a stand proof
that for a reversible heat engine operating over a Carnot cycle
between two temperature and ,the ratio of the heat taken in
at the higher temperature to that given out at the lower temperature
is proportional simply to the ratio of the same function of
each of the two temperatures. . where is a function only of
,and is the same function only of ,independent of the particular
properties of the working fluid. William Thomson(later Lord
Kelvin) realized,1n 1848,that this relation could be used to
define the ration of any two temperatures. The values of the
temperatures would depend upon the functional form ,but by taking
the simplest possible form of the function he defined a temperature,
which he called thermodynamic temperature, T ,by the relation
.Thermodynamic temperature thus has the property that ratios
of T are defined in terms of the properties of reversible heat
engines and are independent of the working substance. The definition
of the quantity thermodynamic temperature then has to be completed
by assigning a particular numerical value to an arbitrary fixed
point of temperature, triple point of the water. So the real
meaning of the temperature is a physical quantity which is fundamental
for the field of thermodynamic and is directly related to the
basic laws of thermodynamics.[5]
In principle ,any suitable thermodynamic equation may be used
as the basis for a thermometer, such as Acoustic thermometer,
thermal noise thermometer, gas thermometer, radiation thermometer,
etc.
However, with the exception of the radiation thermometers used
at high temperature, thermodynamic thermometers cannot arrive
the highest precision desired, and are complex and time consuming
to use. To overcome these difficulties, the above empirical
temperature scale was defined as ITS by (CIPM) under the convention
du Metre,the founding treaty for the SI,and was regularly revised
with the current version agreed to in 1990,and known as ITS90.
The ITS are empirical temperature scales giving a close approximation
to the known thermodynamic scale, but are more precise and easier
to use. Now all temperature measurement should be traceable
to the current ITS.
[1]M. F. Behar ,Temperature and Humidity measurement and control
,Instruments publishing company,113-122, (1932)
[2] F. Sherwood Taylor, The origin of the thermometer , Annals
of Science, Vol.5, 129-156
[3]Thomas D. McGee ,Principles and Methods of Temperature Measurement,1988
[4] J. Cleak Maxwell,Theory of Heat,1916
[5] T.J. Quinn,Temperature,1990
[6] EZER,Griffiths,Charles ,Method of Measuring temperature,1947 |
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