Download or read book A Short Course of Experiments in Physical Measurement Volume 1 written by Harold Whiting and published by Rarebooksclub.com. This book was released on 2013-09 with total page 66 pages. Available in PDF, EPUB and Kindle. Book excerpt: This historic book may have numerous typos and missing text. Purchasers can usually download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1890 edition. Excerpt: ...By measuring the fall thus produced, the pressure of the vapor of various liquids at different temperatures may be determined. Another way to illustrate the pressure exerted by the vapor, of a liquid is to pour a little of the liquid into a flask, so that it may evaporate into the air which the flask contains. If the flask is corked tightly as soon as the liquid is poured in, a considerable pressure may be generated. In fact, explosions sometimes occur from this cause. To measure the pressure, a tube may be passed through the cork into some mercury in the bottom of the flask (see Fig. 67), and the liquid should be injected by means of a medicine-dropper passing through the cork beside this tube, so as to avoid losing the pressure generated by evaporation before the cork can be put into its place. It has been found by experiment that the quantity of liquid.which evaporates in a flask already containing air, and the pressure which it generates, are exactly the same as in a space from which the air has been completely exhausted. This discovery (known as Dalton's Law) is believed to show that the molecules of a gas occupy very little space in comparison with the space between them, into which a liquid may evaporate. In any case, the height to which the mercury column is raised in Fig. 67 is the same as its depression in Fig. 66, other things being equal. We shall make use of this fact to determine roughly the pressure of a vapor at various temperatures. We have seen that when a liquid evaporates into a confined space filled with air, the pressure of the air is increased. It is evident that in an open flask the air must expand until the combined pressure of the air and the vapor inside becomes equal to the atmospheric pressure outside. If...