Centigrade scale

The name formerly used for the Celsius scale. The

name is not now used in International System of

Units (SI) but is often used by meteorologists.

Fahrenheit scale

A temperature scale for which the ice point is at 32°F

and the steam point at 212°F. Originally the zero was

obtained in a freezing mixture and another point was

fixed at 96° for blood temperature.

Rйaumur scale

A temperature scale in which the ice point is at 0° and

the steam point at 80°.

ideal gas scale

A scale in which changes of temperature are

measured either by changes of pressure, or changes

of volume, for gases operating at pressure low

enough for the gases to behave as ideal gases. The

Celsius temperature θ is defined on the scale by:

(pV )

− (pV )

θ =

0

0

×100

(pV )

−

(pV )

100

0

absolute scale

A thermodynamic temperature scale in which the

lower fixed point is absolute zero of temperature and

the interval is identic with that on the Celsius scale.

The temperature on the absolute scale is obtained by

adding to u, the Celsius temperature, 1/a where a is

the coefficient of expansion of a gas at constant

pressure. This gives a scale on which the ice point is

273.15°; i.e.

°A = °C + 273.15.

The absolute scale was often called the Kelvin scale

and temperatures measured in °A or °K. In SI units

temperature is measured in kelvins (K) by defining

the triple point of water as 273.16 K. The ice point is

then 273.15 K. The kelvin has the same size as the

degree absolute.

fixed points

Those points on a temperature scale which are fixed

and which can be referred to a given property of a

substance. The two main fixed points are the ice

point and the steam point.

ice point

That fixed point on a

temperature scale at which

pure solid water (ice) and pure liquid water are in

equilibrium at 101 325 N m-2 (760 mm Hg). It may

be more simply described as the melting point of

pure ice at standard pressure (101 325 N m-2 or 760

mm Hg).

steam point

That fixed point on a temperature scale at which

pure water boils at standard pressure (101 325 N m-

2; 760 mm Hg). This is 100° on the Celsius scale.

zinc point

A fixed point on an international temperature scale,

fixed at the temperature at which zinc changes from

liquid to solid (the freezing point of zinc) at standard

pressure (101 325 N m-2). This corresponds to

419.58 °C.

international

A practical scale which is as near as possible to the

temperature scale

thermodynamic scale but easily referable to a series of

fixed points.

Triple point of hydrogen

-259.34 °C

Boiling point of neon

-246.048 °C

Triple point of oxygen

-218.789 °C

Boiling point of oxygen

-182.962 °C

Triple point of water

0.01°C

Boiling point of water

100.0 °C

Freezing point of zinc oil

419.58 °C

Freezing point of silver

961.93 °C

Freezing point of gold

1064.43°C

Below 630°C platinum resistance thermometer; up to