A Textbook of Inorganic Chemistry (Paperback)

This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1906 Excerpt: ...walls of these tubes small Platinum wires are melted', and these serve as the poles of an induction apparatus. If sparks are passed through these tubes, the gas commences to glow and gives its characteristic spectrum. Hydrogen glows with a red light, and Nitrogen with a violet light. If one of these glowing gases be held before the slit in tube A, the spectrum it forms can be examined. The Hydrogen spectrum is seen to consist of a red, a blue and a green line; the Nitrogen of a great number mostly in the violet, etc. Absorption spectra., Before this form of spectrum can be understood, absorption of light must be explained. Bodies are either opaque or transparent. A transparent body is one that offers no resistance to the passage of light (glass). An opaque body offers resistance to the passage of light. The light which acts upon an opaque body is either reflected or, penetrating into the body, is converted into other kinds of energy (heat, chemical energy). This is the extinction or absorption of light. Photo-thermal absorption occurs when light entering a body is converted into heat. Photo-chemical absorption is the conversion of the light entering a body into chemical energy. Some transparent bodies transmit all kinds of light-rays practically unabsorbed; such transparent bodies are therefore white or--as they are usually called--colorless ( window-glass); but not all bodies do this. Some are transparent to certain rays, while others of a different wavelength are absorbed. The rays not absorbed determine the color of the light after passing through the body. A monochromatic or a mixed color will be produced according to the rays that pass through. Use is made of this fact in analytical chemistry. Sodium imparts a yellow color to the flame, Potassium a vio...