The threshold of science : a variety of simple and amusing experiments illustrating some of the chief physical and chemical properties of surrounding objects, and the effects upon them of light and heat / by C.R. Alder Wright.

  • Wright, C. R. Alder (Charles Romley Alder), 1844-
Date:
1891
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Licence: Public Domain Mark

Credit: The threshold of science : a variety of simple and amusing experiments illustrating some of the chief physical and chemical properties of surrounding objects, and the effects upon them of light and heat / by C.R. Alder Wright. Source: Wellcome Collection.

    201/464 (page 171)
    sodium chloride and aimnoniiim nitrite, which latter substance is a ternary compound of nitrogen, hydrogen, and oxygen; being unstable, it is immediately decomposed by the heat, forming a mixture of water vapour and nitrogen gas. The latter may be collected over water at the pneumatic trough, like oxygen. Expt. 184. Another Method.—Ordinary atmospheric air is shown by Expt. 148 to be a mixture of oxygen and nitrogen, from which the former can be removed by the action of pyrogallic acid dissolved in caustic soda. Many other substances may be employed in the same way; for instance, phosphorus. Float on water a large bung, and on it put a bit of phosphorus the size of a pea, carefully dried in blotting paper. Touch the phosphorus with a hot wire, and it will begin to burn; as soon as this occurs hold over the bung and burning phosphorus a jar or bell-shaped vessel (fig. 78), so that the bottom of the jar just touches the water. At first the heat of the burn- ing phosphorus expands the air, and drives a httle out, so that a few bubbles escape under the edge of the jar; the jar should then be lowered so that its mouth is an inch or two under water. As the phosphorus burns it ab- sorbs the oxygen, and the compound formed produces a white cloud of solid oxide of phosphorus particles ; so that the bullc of gas in the jar diminishes from the removal of the oxygen. Soon the flame of the phosphorus goes out, all the oxygen being consumed; let the jar remain at rest for half an hour ; by that time the fumes will have all subsided, and the gas in the jar will be clear ; it will consist of nearly pure nitrogen. (Compare Expt. 169. Caution.) Expt. 185. To show that Nitrogen extinguishes Flame.— Prepare nitrogen in a bell jar with a stopper in the top; when the gas is clear remove the stopper, taking care that the jar is sunk so deep in the basin that the water stands at the same level iaside and out. Introduce a lighted candle by a wire; the candle will be extinguished, just as in Expts. 71 and 149. Expt. 186. To reproduce Air from Nitrogen and Oxygen.— Prepare some nitrogen, and transfer it to a jar so as to fill it about four-fifths full; this is done by depressing the jar containing the