Sinossi
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. 1888 Excerpt: ... and is pressed by, the sides of the vessel. A gas cannot be contained in an open vessel, unless the space outside the vessel contains some fluid which exerts pressure on the gas. For example, if an open vessel containing a gas be placed in a space exhausted of air, the gas will expand and fill the whole space. On the other hand, if a vessel containing gas be held mouth downwards in water, the gas will remain in the vessel. It is to be observed that changes due to such causes as chemical reactions, absorption of gases by liquids, etc., are not considered in this treatise. 77. Density.--If we take equal volumes of two bodies, and find that the mass of one is greater than the mass of the other, the body which has the greater mass is said to be denser than the other. Thus, if we compare a cubic foot of iron with a cubic foot of wood, we find that the iron has the greater mass, and is therefore denser than the wood. Similarly mercury is denser than iron, iron than water, water than air. The Density of a body is the mass contained in unit volume. If we take a foot as the unit of length, a cubic foot will be the corresponding unit of volume. Let p be the density of a body of mass M, whose volume is V cubic feet. Then the mass of 1 cubic foot is p, „ „ 2 „ feet „ 2p, „,, o „ feet „ op, and so on. Therefore the mass of V cubic feet is Vp, or M = V/ (29) Since the volume of a given mass of a liquid is constant, its density is also constant, but different liquids have different densities. In a gas the volume varies with the pressure, and therefore the density also varies. If we divide both sides of (29) by (1) p, (2) V, it takes the forms V = andP=,.... (29') p V which show us that the volume of a given mass varies in versely...
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