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Gases and Vapors

.05701 ... .03244 .03234 .622 .2777 .504 Steam Air (atmospheric) Hydrogen.

Oxygen .4805 Carbonic oxide. .2450 .2374 Carbonic acid. .2163 3.4090 Marsh gas. .5929 .2175 Olefiant gas .2438 .4040 Nitrogen LATENT HEAT OF VARIOUS BODIES.-Latent heat is the quantity of heat which must be communicated to a body in a given state in order to convert it into another state without changing its temperature. The latent heat of a liquid body expresses the number of thermal units required to change it from the solid to the liquid form. The latent heat of a vapor expresses the number of thermal units required to change the body from the liquid to the gaseous condition. The following is a short table of latent heat:

Water Sulphur Lead..

Mercury 162.65 | Steam 16.68 Alcohol vapor 9.66 Silver Colors and Temperatures. The following is a table of colors expressive of the corresponding high temperature reduced to Fahrenheit: Faint red Dull red Brilliant red Cherry red Bright cherry red.

Orange Fahr.

Fahr. 960º Bright orange 2190° 1290° White heat 2370° 1470° Bright white heat 2550° 1650° Brilliant white 2730° 1830° Melting point of cast-iron 2786° 2010° | Greatest heat of iron blast furnace. .3300° Ether boils at 104; alcohol at 173.5; nitric acid at 210; oil of turpentine at 304; phosphorus at 554; sulphur at 570; and mercury at 656. Eggs are hatched at 104° of heat.

Polished steel is a blue color at 580° of heat, and at 460° it is straw color. A bath at 150° scalds, but hot air at 260º is not painful. The usual heat of tea and coffee when drunk is 110°. Hemp, cotton, waste, matting, etc., with oil and lamp-black generate heat, and finally ignite spontaneously when exposed to air.

Solids slightly dilate by enlarging the orbits of the gases in their pores. Further enlargement by more heat breaks up their structure, and ultimately renders the whole fluid as a volume of excited atoms. The degree of excitement to effect this varies with the structure. Mercury, alcohol, ether, etc., have feeble structures, and platinum, gold, iron, etc., impregnable structures.

Cork and wood from boiling water water may be handled, but not metals, though both effect the thermometer equally. The heat conducting powers of metals are: gold, 1,000°; platinum, 981; silver, 973; copper, 898.2; iron, 374.3; zinc, 363; tin, 303.9; lead, 179.6; marble, 23.6; porcelain, 12.2; fire clay, 11.4. All hot bodies distribute their heat or atomic motion to other atoms around. This depends on the roughness of the surface as exposing the greatest number of points to surrounding atoms. Metals radiate the least, lamp-black, paper, and glass the most.

The visible radiations from heated bodies are reflected like light, but they do not pass through transparent bodies.

A poker laid over a fire concentrates the heat of passing smoke, and creates a draught through the fire.

Water is called hard when, from containing too much carbonic acid, it holds lime in solution.

A phial of water in freezing, parts with as much atomic motion as would make an equal bulk of gold white hot.

Water in heating makes two currents, one up the sides of the vessel and another down the centre.

A scientist name Chabert is reported to have entered an oven, the air in which was 500º. Blagden and others in rooms at 289º experienced no discomfiture. Fish can live in hot baths up to 158°. Trees will grow in a bath at 174°; flowers near a volcano at 210°, and water plants are found in boiling springs. Extreme cold produces the same perception on the skin as great heat. When mercury is frozen at 40° below zero the sensation to the skin is the same as that of touching red-hot iron.

When water freezes it forms itself into crystals with interstices and expands; hence ice swims, and is 8 parts in 100 lighter than water. Salt renders snow liquid, and the liquidity absorbs motion from surrounding bodies, so as to freeze them.

The conductivity of metals as regards heat is as follows: Gold being 100; platinum, 98; silver, 97; copper, 90; iron, 37; zinc, 36; tin, 30; lead, 18. Ice melts at 32° Fahrenheit; water boils at 212°; alcohol at 174; leads melts at 594°; brass at 2233; and iron at 3479; Blood heat is 98°; heat of a common fire 1140°; and that of the globe 50.