. The railroad and engineering journal . enclosed vessel, like acovered tea-kettle or a steam-boiler, what t^ccurs ? . The steam rises and fills the space above the if it cannot escape, increases in pressure. The tempera-ture of both the water and the steam rises with the pressure,and will continue to do so as long as the heat is increased, oruntil the steam can escape, or the vessel is exploded. Theboiling point also rises .as the steam prc-sure increases. •In common practice it is cenerally at 15 lbs. rer square inch, butthe average atmDspheric pressure is, nior- rc
. The railroad and engineering journal . enclosed vessel, like acovered tea-kettle or a steam-boiler, what t^ccurs ? . The steam rises and fills the space above the if it cannot escape, increases in pressure. The tempera-ture of both the water and the steam rises with the pressure,and will continue to do so as long as the heat is increased, oruntil the steam can escape, or the vessel is exploded. Theboiling point also rises .as the steam prc-sure increases. •In common practice it is cenerally at 15 lbs. rer square inch, butthe average atmDspheric pressure is, nior- rccurately, pounds ▼ol. LXI. No. II.] ENGINEERING JOURNAL. 522 Question 37. How can this effect ht itlustralai/Answer. It can be shown if we take a glass tubi- T, fig. 7,closed at its lower end, and put a small quantity of water in it,and then force a cork, C, which fits the tube, or a wad of cottonsaturated with tallow, down on top of the water, and then holdthe lower end of the tube over a spirit lamp or gas flame, and Fig- 7-. , wh< ^ IPH! pounds ■.; Fig. 9. posing, as we did before, that no power is required to overcomeits friction in the cylinder—then, if the pressure of the steamthus admitted below the piston would just balance the pressure heat it slowly, so as not to crack the glass tube. Bubbles ofsteam will then form at the bottom of the water, as shown infig. 8. These will rise to the top, and will soon force the corkor wad of cotton upward with more or less violence, in pro-portion to the tightness with which it fits the tube, and therate at which the water is boiled. Question 38. Is there any pressure which corresponds to thetemperature of steam and water? Yes. There is a fixed pressure for every tem- contact with water, and its pressurecannot be increased or diminished without at the same timeheating or cooling the water, and the higher the temperatureof the water the greater will be the corresponding steam pres-sure. Thus water at 212
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Keywords: ., bookcentury1800, bookdecade1880, booksubjectrailroa, bookyear1887
