Equivalent \E*quiv"a*lent\ ([-e]*kw[i^]v"[.a]*lent), n.
1. Something equivalent; that which is equal in value, worth,
weight, or force; as, to offer an equivalent for damage
done.
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He owned that, if the Test Act were repealed, the
Protestants were entitled to some equivalent. . . .
During some weeks the word equivalent, then lately
imported from France, was in the mouths of all the
coffeehouse orators. --Macaulay.
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2. (Chem.) That comparative quantity by weight of an element
which possesses the same chemical value as other elements,
as determined by actual experiment and reference to the
same standard. Specifically:
(a) The comparative proportions by which one element
replaces another in any particular compound; thus, as
zinc replaces hydrogen in hydrochloric acid, their
equivalents are 32.5 and 1.
(b) The combining proportion by weight of a substance, or
the number expressing this proportion, in any
particular compound; as, the equivalents of hydrogen
and oxygen in water are respectively 1 and 8, and in
hydric dioxide 1 and 16.
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Note: This term was adopted by Wollaston to avoid using the
conjectural expression atomic weight, with which,
however, for a time it was practically synonymous. The
attempt to limit the term to the meaning of a
universally comparative combining weight failed,
because of the possibility of several compounds of the
substances by reason of the variation in combining
power which most elements exhibit. The equivalent was
really identical with, or a multiple of submultiple of,
the atomic weight.
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3. (Chem.) A combining unit, whether an atom, a radical, or a
molecule; as, in acid salt two or more equivalents of acid
unite with one or more equivalents of base.
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Mechanical equivalent of heat (Physics), originally defined
as the number of units of work which the unit of heat can
perform, equivalent to the mechanical energy which must be
expended to raise the temperature of a pound of water one
degree Fahrenheit; later this value was defined as one
British thermal unit (B.t.u). Its value was found by
Joule to be 772 foot pounds; later measurements give the
value as 777.65 foot-pounds, equivalent to 107.5
kg-meters. This value was originally called Joule's
equivalent, but the modern Joule is defined differently,
being 10^7 ergs. The B.t.u. is now given as 1,054.35
absolute Joules, and therefore 1 calorie (the amount of
heat needed to raise one gram of water one degree
centigrade) is equivalent to 4.186 Joules.
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Note: The original definition of the Mechanical equivalent of
heat in the 1913 Webster was as below. The difference
between foot pounds and kilogram-meters ("on the
centigrade scale") is puzzling as it should be a factor
of 7.23, and the figure given for kilogram-meters may
be a mistaken misinterpretation of the report. -- PJC:
The number of units of work which the unit of heat can
perform; the mechanical energy which must be expended
to raise the temperature of a unit weight of water from
0[deg] C. to 1[deg] C., or from 32[deg] F. to 33[deg]
F. The term was introduced by Dr. Mayer of Heilbronn.
Its value was found by Joule to be 1390 foot pounds
upon the Centigrade, or 772 foot pounds upon the
Fahrenheit, thermometric scale, whence it is often
called Joule's equivalent, and represented by the
symbol J. This is equal to 424 kilogram meters
(Centigrade scale). A more recent determination by
Professor Rowland gives the value 426.9 kilogram
meters, for the latitude of Baltimore.
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Heat \Heat\ (h[=e]t), n. [OE. hete, h[ae]te, AS. h[=ae]tu,
h[=ae]to, fr. h[=a]t hot; akin to OHG. heizi heat, Dan. hede,
Sw. hetta. See Hot.]
1. A force in nature which is recognized in various effects,
but especially in the phenomena of fusion and evaporation,
and which, as manifested in fire, the sun's rays,
mechanical action, chemical combination, etc., becomes
directly known to us through the sense of feeling. In its
nature heat is a mode of motion, being in general a form
of molecular disturbance or vibration. It was formerly
supposed to be a subtile, imponderable fluid, to which was
given the name caloric.
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Note: As affecting the human body, heat produces different
sensations, which are called by different names, as
heat or sensible heat, warmth, cold, etc., according to
its degree or amount relatively to the normal
temperature of the body.
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2. The sensation caused by the force or influence of heat
when excessive, or above that which is normal to the human
body; the bodily feeling experienced on exposure to fire,
the sun's rays, etc.; the reverse of cold.
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3. High temperature, as distinguished from low temperature,
or cold; as, the heat of summer and the cold of winter;
heat of the skin or body in fever, etc.
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Else how had the world . . .
Avoided pinching cold and scorching heat! --Milton.
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4. Indication of high temperature; appearance, condition, or
color of a body, as indicating its temperature; redness;
high color; flush; degree of temperature to which
something is heated, as indicated by appearance,
condition, or otherwise.
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It has raised . . . heats in their faces. --Addison.
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The heats smiths take of their iron are a blood-red
heat, a white-flame heat, and a sparkling or welding
heat. --Moxon.
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5. A single complete operation of heating, as at a forge or
in a furnace; as, to make a horseshoe in a certain number
of heats.
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6. A violent action unintermitted; a single effort; a single
course in a race that consists of two or more courses; as,
he won two heats out of three.
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Many causes . . . for refreshment betwixt the heats.
--Dryden.
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[He] struck off at one heat the matchless tale of
"Tam o' Shanter." --J. C.
Shairp.
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7. Utmost violence; rage; vehemence; as, the heat of battle
or party. "The heat of their division." --Shak.
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8. Agitation of mind; inflammation or excitement;
exasperation. "The heat and hurry of his rage." --South.
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9. Animation, as in discourse; ardor; fervency; as, in the
heat of argument.
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With all the strength and heat of eloquence.
--Addison.
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10. (Zool.) Sexual excitement in animals; readiness for
sexual activity; estrus or rut.
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11. Fermentation.
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12. Strong psychological pressure, as in a police
investigation; as, when they turned up the heat, he took
it on the lam. [slang]
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Animal heat, Blood heat, Capacity for heat, etc. See
under Animal, Blood, etc.
Atomic heat (Chem.), the product obtained by multiplying
the atomic weight of any element by its specific heat. The
atomic heat of all solid elements is nearly a constant,
the mean value being 6.4.
Dynamical theory of heat, that theory of heat which assumes
it to be, not a peculiar kind of matter, but a peculiar
motion of the ultimate particles of matter.
Heat engine, any apparatus by which a heated substance, as
a heated fluid, is made to perform work by giving motion
to mechanism, as a hot-air engine, or a steam engine.
Heat producers. (Physiol.) See under Food.
Heat rays, a term formerly applied to the rays near the red
end of the spectrum, whether within or beyond the visible
spectrum.
Heat weight (Mech.), the product of any quantity of heat by
the mechanical equivalent of heat divided by the absolute
temperature; -- called also thermodynamic function, and
entropy.
Mechanical equivalent of heat. See under Equivalent.
Specific heat of a substance (at any temperature), the
number of units of heat required to raise the temperature
of a unit mass of the substance at that temperature one
degree.
Unit of heat, the quantity of heat required to raise, by
one degree, the temperature of a unit mass of water,
initially at a certain standard temperature. The
temperature usually employed is that of 0[deg] Centigrade,
or 32[deg] Fahrenheit.
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