Page:Popular Science Monthly Volume 7.djvu/717

Rh the flame wherefrom it was deposited. It is well known that the temperature of the flame varies in various places, and Magnus's experiments have proved that from heavy hydrocarbons at a less high temperature a hydrogenous tarry product besides hydrocarbon is also eliminated. The soot, whose analysis I give, was obtained from a bat's-wing burner by allowing a small silver basin, filled with water, to dip for about two or three minutes in the flame. Benzine removed traces of a solid yellow body, but the small amount of it prevented its being further investigated. Alcohol, and alcoholic solution of caustic potash, and dilute sulphuric acid, dissolved nothing.

After being carefully and repeatedly washed with boiling water and dried at 130°, 0.206 yielded: Carbonic acid, 0.6985; water, 0.0195; ash, 0.0020—which amounts in 100 parts to.

I attribute the presence of oxygen to a small amount of water, which, even at 130°, was still retained, and this, when deducted, gives the composition of 100 parts of soot free from water and ash as consisting of carbon, 99.095; hydrogen, 0.905.

This analysis is in accordance with the chemical composition of the soot of the flame, and with the well-known behavior of heated hydrocarbons.

2. "How could the light of a flame be as transparent as in reality it is, if it was filled with solid carbon-particles?" asks Dr. Frankland.

In reply to this, it must be admitted that one is able to read the writing held behind the flame of a bat's-wing burner. It is, however, easily observable that the flame is more transparent in the lower non-luminous portion. The reading becomes also more difficult through a flame of greater thickness, and impossible through the flame of a candle or petroleum-burner. If, as is proved hereby, the transparency of a flame is only very limited, it may also be remembered that one can also read the same writing through media which are known to be filled with solid particles. The fact that solid bodies are by preference apt to become light-radiating is not at all changed by this, and thus far it is demonstrated only that there can be but one solid body to which the luminosity of flame can be attributed. If we consider, therefore, all the facts, we can draw only one conclusion, namely, that the light of our illuminating flame comes from incandescent carbon-molecules, and that the old view is still to be retained.

Experience teaches that, for the artificial production of light, a high temperature is requisite before all things. Temperature is, however, that part of the total heat of a body which influences the surrounding