Page:International Library of Technology, Volume 93.djvu/53

Solution.—Substituting the given values in formula 2,

$P=\left({\frac {80\times 14}{560}}+{\frac {60\times 26}{520}}\right){\frac {600}{20}}=150$ lb. per sq. in. Ans.

Example 3.—Twelve cubic feet of gas at a pressure of 120 pounds per square inch, and at a temperature of 260° F., is compressed, together with 25 cubic feet of the same gas at a pressure of 81 pounds and a temperature of 215° F., until the final temperature is 40° F. and the pressure is 100 pounds; what is the final volume of the gas?

Solution.—Substituting the given values in formula 3,

$V=\left({\frac {120\times 12}{720}}+{\frac {81\times 25}{675}}\right){\frac {500}{100}}=25$ cu. ft. Ans.

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EXAMPLES FOR PRACTICE

1. Two vessels contain air at pressures of 60 and 83 pounds per square inch. The volume of each vessel is 8.47 cubic feet. If all the air in both vessels is removed to another vessel and the new pressure is 100 pounds per square inch, what is the volume of the vessel, the temperature being the same throughout? Ans. 12.11 cu. ft.

2. A vessel contains 11.83 cubic feet of air at a pressure of 83.3 pounds per square inch. It is desired to increase the pressure to 40 pounds per square inch by supplying air from a second vessel, which contains 19.6 cubic feet of air at a pressure of 60 pounds per square inch. What will be the pressure in the second vessel after the pressure in the first has been raised to 40 pounds per square inch? Ans. 55.96 lb. per sq. in.

3. If 4.8 cubic feet of air having a pressure of 52 pounds per square inch and a temperature of 170° is mixed with 13 cubic feet having a pressure of 78 pounds per square inch and a temperature of 265°, what must be the volume of the vessel containing the mixture, in order that the pressure of the mixture may be 30 pounds per square inch and the temperature 80°? Ans. 32.31 cu. ft.

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EBULLITION AND VAPORIZATION

45. All liquids capable of boiling are also capable of evaporation. Boiling, or ebullition, is the formation of vapor within the mass of a liquid, due either to the addition of heat or to the reduction of the pressure below that of the boiling point of the liquid. For the most part, boiling takes place in that part of the liquid in contact with the surface through which the heat is transmitted to the liquid.