. A text book of physics, for the use of students of science and engineering . ntimetres. Having charged B with sufficient liquid to obtain saturatedonditions and measured the difference in mercury levels, lower B in the>ath. It will be found that the effect is to diminish the volume of theapour space ; some of the vapour condenses into the liquid state, and onaeasuring the difference in levels of the mercury in A and B, this will beound to be the same as at first. Now elevate B, thus increasing the vapourpace ; this should not be carried to excess, or the whole of the liquid wille evaporat
. A text book of physics, for the use of students of science and engineering . ntimetres. Having charged B with sufficient liquid to obtain saturatedonditions and measured the difference in mercury levels, lower B in the>ath. It will be found that the effect is to diminish the volume of theapour space ; some of the vapour condenses into the liquid state, and onaeasuring the difference in levels of the mercury in A and B, this will beound to be the same as at first. Now elevate B, thus increasing the vapourpace ; this should not be carried to excess, or the whole of the liquid wille evaporated and the vapour will be unsaturated. Again measure theifference in mercury level and compare with the initial reading. Theesult shows that, so long as the vapour is saturated, the pressure at theonstant temperature of the room remains unaltered. Expt. 100.—Maximum pressure of aqueous vapour at lower temperatures,n Fig. 432. ABC is a closed bent tube having a bulb at C. The portion BDnd part of the bulb contains mercury ; the portion AB is a Torricellian 452 HEAT CHAP. B. vacuum (p. 259). The bulb contains some water lying on the surface, ofthe mercury and the remainder of the bulb contains vapour of water. Ascale is attached to the straight part of the tube, and the bulb and bentpart of the tube are immersed in a beaker of water. The water in thebeaker may be heated by means of a bunsen flame, and its temperature is measured by a thermometer E, placed nearthe bulb. The straight part of the tubeand the scale are shielded from the flame andfrom the beaker. The aqueous vapour in the bulb is saturatedso long as there is any water in the bulb, andits pressure is equivalent to the mercury headbetween the surfaces in B and C. The level inB is read directly on the scale; that in thebulb is taken by means of a metal rod 20 , arranged to slide up and clown along thescale. The lower end of the rod is adjusted tothe mercury level in C, and the top end of therod is read on the sc
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