Textbook on 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. 1852 Excerpt: ... does this expansion take place with an inconsiderable force. If a flaccid bladder be placed, as in Fig. 192, with several heavy leaden weights put upon it, as soon as it is caused to dilate by removing the pressure, it will push up the weights. Nor does it lose its elastic force or spring by being long pent up in close vessels. Some of the old chemists kept air compressed in copper globes for months, and found that, as soon as an opening was made for it, it expanded to its original dimensions. Let there be taken a glass bulb, a (Fig. 193), the open neck of which, b, dips beneath some water in ng. 193 a jar, e, and let the bulb and tube be full of water, with the exception of a small space occupied by atmospheric ah On covering the apparatus with an air-pump receiver, d, and exhausting, the bubble of air, a, gradually expands, and after a time, as the action of the machine is continued, fills the entire glass, both bulb and tube; but as the pressure is restored, it contracts again, and goes back to its original size. By taking advantage of the expansibility of air undeT Fig. 194. reduction of pressure, we are able to dem-Kg. i95. onstrate its existence in the pores of many bodies; thus, if we place in glasses of water an egg (Fig. 194), an apple (Fig. 195), or other such objects, and, covering them with a receiver, exhaust, we shall see innumerable bubbles of air escaping through the water. The same observation may be made in the case of many liquids which hold gaseous substances dissolved. A glass of ale placed in an exhausted receiver How may the elasticity of air be shown by an India-rubber bag? Give an illustration of the amount of this force. How may the presence of air be detected in the pores of solid bodies 1 How may air be shown to exist dissolved ...