_Radiating_
_Material._ _Power._
Lampblack 100
Water 100
Writing paper 98
Glass 90
Tissue paper 88
Ice 85
Wrought lead 45
Mercury 20
Polished lead 19
Polished iron 15
Gold, silver 12
Copper, tin 12
From the above tables, it will be seen that water, being an excellent
radiator, and of great specific heat, and iron a good conductor, these
qualities, together with the small cost of the materials, combine to
render them efficient, economic and convenient for the transmission and
distribution of artificial heat.
By adopting certain standards we are enabled to define, compare and
calculate so as to arrive at definite results, hence the adoption of a
standard unit of heat, unit of power, unit of work, etc.
The standard unit of heat is the amount necessary to raise the
temperature of one pound of water at 32° Fahr. one degree, _i.e._, from
32° to 33°.
Specific heat is the amount of heat necessary to raise the temperature
of a solid or liquid body a certain number of degrees; water is adopted
as the unit or standard of comparison. The heat necessary to raise one
pound of water one degree, will raise one pound of mercury about 30
degrees, and one pound of lead about 32 degrees.