SWEETENED CONDENSED MiILK—CONDENSING 91 
According to Kent! the relation of altitude to atmospheric 
pressure per square inch is as follows: 
Pounds Pressure 
Altitude Per Square Inch 
aN bee ete Wag Nt Xoo Dap Nae ae CoaA Pe rsh SA ar OPES eh Aree Ty RET Cork ate 14.7 
TIN TELAWOVersea-lEVEls cota craueueks Gee waged ae 14.02 
Aamile above Sea level news sees ok ta eed a ee 13.33 
Tile aboneser levels i) ua page Saas beste ad 12.66 
Ig) MTT LCSD OMGaS eae clic mon rant met a Anaya 12.02 
LermbeseabOve Sea; LEVEL pac c eee ek ee ee was 11.42 
IS miles abame sew levelic. cas 458 end Ate eo ye eane x 10.88 
2 miles above sea level 9.80 
“For a rough approximation we may assume that the pres- 
sure decreases one-half pound per square inch for every 1,C00 
feet of ascent.” 
The absolute pressure in the pan of a factory located at 
Omaha, Neb., with an altitude of 1,016 feet above sea level, and 
condensing in an actual vacuum of twenty-five inches, would 
then be as follows: 
Atmospheric pressure = 14.7 — .5 = 14.2 pounds per square 
inch. 
Absolute vacuum = 14.2 «2.04 = 28.97 inches. 
14.2 % (28.97 — 25) : 
Abe Frees = ass —— () c 
Absolute pressure = WR OF = 1.95 pounds 
per square inch, 
Relation of Steam Pressure in Jacket and Coils, Water in 
Condenser, Temperature in Pan and Vacuum, to Rapidity of 
Evaporation.— The temperature of the vapors in the vacuum pan 
depends directly upon the pressure or vacuum under which they 
are generated. ‘The more nearly complete the vacuum and, there- 
fore, the lower the pressure, the lower is the temperature, and, 
other conditions being the same, the more rapid the evaporation. 
The pressure in turn is governed by the capacity of the vacuum 
pump, the tightness of the joints, the steam pressure in jacket 
and coils and the amount and temperature of the water in the 
condenser. 
t Mechanical Engineer's Pocket-Book, p. 681. 
