PRODUCTS OF COMBUSTION.
Carbon, en Air (69.6) Oxygen, 16.0 Carbonic acid, 22.0 Nitrogen, 53.6 Nitrogen, 53.6 75.6 75.6 Or, assuming carbon as unity: Carbon, Air (11.6) Oxygen, 2.667 Carbonic acid, 3.667 Nitrogen, 8.933 Nitrogen, 8.933 12.600 12.600 Carbon, therefore, requires about twelve times its own weight of air for perfect com bustion.
2. Amount of heat found that 1 lb. carbon produced heat equal to 1° F. in 14,220 lbs. of water. Other observations agree very closely. This may be otherwise stated thus: 1 lb. carbon will raise from freezing to boiling' point (32° to 14220 212° = 180°) — = 79 lbs. water; from mean temperature to boiling-point (60° 180 0 212 = 152°) 1422 = 93.5 lbs. water; will boil off in steam from mean temperature 152 (60° to 212° = 152°, add latent heat in steam, 965° = 1117°), 12.73 lbs.water; 1117 and will boil off in steam from boiling-point (latent• heat in steam 965°) 14.74 965 pounds.
3. Utmost Temperature or Intensity of Heat from we suppose the com bustion effected in a space inclosed by non-conducting material, so that all the heat produced by 1 lb. carbon is retained by the products of its combustion. Caloric sufficient to raise 14,220 lbs. water 1°.F. is thus compressed, as it were, into 12.6 lbs. of carbonic acid and nitrogen. To determine the temperature thus produced, we require to know the specific heat of this gaseous compound, that of water being 1.
3.667 lbs. carbonic acid. • Specific heat .2210 8.933 " nitrogen. , ..... .2754 12.600 " products of combustion. • Mean sp. " .2596 14,20° on water at 1.000 specific heat, will give 54,776° on these products per pound.
54776 weight. Distributed over 12.6 lbs., this heat will raise the to 12.0 = 4347° F., which is therefore the utmost intensity of heat attainable in burning carbon, sup posing no loss by absorption or radiation.
4. Effect of Excess of Air.-Excess of air has been proved to have no effect on the quantity of heat produced where combustion is perfect; but the intensity of temperature is diminished. Suppose two equivalents of air admitted; we then have as the products
of combustion 3.667 lbs. carbonid acid. Specific heat .2210 • 8.933 " nitrogen. " ... : .2754 11.600 ." air in excess. At.2669 .
24.200 " products. Mean sp. " .2631 14,220° on water = 54,048° on this new mixture of gases. But the heat is now diffused over 24.2 lbs. matter instead of 12.6 lbs., 54048 = 2347° F.: the utmost temperature pro ' 24.2 duced by carbon burned in two equivalents of air.
The utmost temperatures attainable, with various proportions of air, are given below, and also the appearance which the interior of the furnace would exhibit. Flame at these temperatures will present the same differences in color.
.
Weight. • Ratio of Fuel Highest Possible I Appearance of a Body exposed to Air. Temperature. to such Temperature.
Carbon. Air.
lbs. lbs.
1. 11.6 Ito 1 4347° Intensely brilliant.
I. 17.4 1 " li 2951 Banding white.
1. 23.2 1 " 2 2= Blight ignition.
1. 29.0 1 " 21 1797 Full cherry red.
I. 34.8 1 " 3 1503 Commencing cherry red.
1. 58. 1 " 5 938 Incipient red.
1. 69.6 1 " 6 758 Black.
5. Effect of Deficiency of Air.-If, before reaching the upper layers of carbon or cinder, the air has partedwith all its oxygen to form carbonic acid with the production of heat, then the carbonic acid combines with part of the remaining carbon to form carbonic oxide, CO (q.v.), but without producing heat. The loss may amount, there fore, to one half of the F.: some have stated it as high as three fourths. If this oxide, when it gets above the F., meet with air before cooling, it burns with a pale blue flame, restoring part of the lost heat; but to what extent has not yet been determined.
G. Effect of Water Present.-Passing into vapor, water absorbs both sensible and latent heat, and thus diminishes the temperature. Heating power is also lost, as prod ucts of combustion are generally passed into the atmosphere at a high temperature.