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KF5JRV > TECH 04.08.16 13:45l 81 Lines 4477 Bytes #999 (0) @ WW
BID : 7112_KF5JRV
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Subj: Early thermometers and temp scales
Path: IW8PGT<CX2SA<ZL2BAU<N0KFQ<KF5JRV
Sent: 160804/1126Z 7112@KF5JRV.#NWAR.AR.USA.NA BPQK1.4.65
Early thermometers and temperature scales
Although a type of thermometer called the thermoscope had been invented in the
late sixteenth century, it was not until the seventeenth and eighteenth
centuries that natural philosophers attempted to develop a standard
temperature-scale according to fixed points, such as the degree of heat in
boiling or freezing water. While many scales were developed, only a few types
persisted in the design and manufacturing of thermometers into the nineteenth
and twentieth centuries. Still familiar to us today, temperature scales
developed by Anders Celsius (1701-44) and Daniel Gabriel Fahrenheit
In a letter to Balthasar de Monconys (1611-1665) dated 1646, Evangelista
Torricelli (1608-1647) described the earliest known sealed liquid-in-glass
thermometer. Developed in Florence, a vibrant commercial center with a rich
glass-blowing culture, the phial of these early thermometers contained glass
balls of different weight to volume ratios.
Small air bubbles trapped in the glass balls would shrink or expand according
to the surrounding liquid, causing the balls to rise or fall in the tube and
indicate temperature. The principles of the Galilean thermometer are based on
the air thermoscope as invented by Galileo Galilei (1564-1642); however,
Galileo did not invent the Galilean thermometer.
Florentine thermometers
The later Florentine thermometer was also a sealed liquid-in-glass design. In
this instance, the expansion and contraction of the thermometer's liquid was
measured against a scale of glass beads that marked the neck of the phial. A
variety of liquids were used to measure temperature, but most thermometers
were filled with water or spirit of wine. This was a colourless spirit, as red
dye tended to soil the tube.
Andrea Mariani, master glass-blower to Ferdinand II, Grand Duke of Tuscany,
produced many of the thermometers used at the Accademia del Cimento (the
Academy of Experiments), which was founded by Ferdinand II in 1657 to conduct
extensive experiments on the conditions of the atmosphere. He claimed his
workshop could produce 50 degree thermometers with uniformity; however,
manufacturing consistent products measuring 100 and 300 degrees proved too
challenging.
Although Florentine scales did not use fixed points, such as the heat of
boiling water, to establish the amount of spirit sealed inside the tube,
thermometers produced in Mariani's workshop are remarkable in that their
temperature readings consistently agree between each other.
Due to Mariani's excellent glass-blowing skills, his Florentine thermometers
produced the same temperature readings with regularity. However, thermometers
made by different glass-blowers used different scales that did not agree when
compared.
In the 1660s, Robert Hooke (1635-1707), at the Royal Society in London,
attempted to construct thermometers that would universally agree at one fixed
point: that at which distilled water started to freeze. He experimented with
several thermometric liquids, such as spirit and mercury, to use inside his
thermometers.
The Isaac Newton (1643-1724) used linseed oil in his sealed-in-glass
thermometers. His scale used three fixed-points: the temperature of air when
water begins to freeze, the heat of blood in the human body and rapidly
boiling water. On Newton's scale, freezing air was 0º, blood heat was 12º and
boiling water was 34º.
Thermometers produced in the eighteenth century sometimes marked the
temperatures of various 'standards' for medical, economic and meteorological
purposes. For example, the long-bulb mercury thermometer made by René-Antonie
Ferchault de Réaumur (1683-1757) listed the temperatures - in his own scale -
of freezing and boiling water, the human body (30ºR), a warm bath (25ºR),
silkworms (19ºR), hothouses (15ºR), a temperate atmosphere (9.5ºR), an
orangery (6ºR), black ice (-4ºR), as well as the coldest temperature
registered in Paris in 1740 (-10.5ºR) and 1776 (-15ºR).
Réaumur divided his thermometer scale according to two standard temperatures:
when water freezes (0º) and boils (80º). The distance between these two points
on the neck of the thermometer was divided into equal increments. Throughout
his career, Réaumur continued to develop and modify his temperature scale, so
that his thermometers from the 1730s differed numerically from those produced
in 1770.
73, Scott kf5jrv
KF5JRV @ KF5JRV.#NWAR.AR.USA.NA
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