STEAM HEATING AND ENGINEERING 145 



2, WATER 



Water is composed of oxygen and hydrogen; it is com- 

 pressible and elastic, but the change is very minute and has no 

 practical consequence. A column of fresh water 27.71 (27 T y^) 

 inches high, at a temperature of 62 degrees Fahr., would 

 exert a pressure, at the bottom, of one pound, while at the 

 same temperature a column of fresh water 33.947 (33 yVbir) 

 feet high, would have a pressure of one atmospheres 

 14.7 Ibs., per square inch at the base. Water is 815 times 

 heavier than air at the sea level with a mean temperature, 56 

 degrees Fahr. Fresh water will boil in a vacuum at a tempera- 

 ture of 72 degrees Fahr.; in the open air at sea level at 212 

 degreees Fahr.; and under a pressure of 15 Ibs. per square inch 

 at a temperature of 234 degrees Fahr. 



Water is the heaviest, or at its greatest density, at about 39 

 degrees Fahr. ; at this point it will expand with either heat or 

 cold. From this fact it is evident that there is a point on either 

 side of this temperature where the water has the same weight, 

 and this point is reached when the water is at 32 degrees and 47 

 degrees Fahr. 



Water will expand in rising from 60 degrees Fahr. to 212 

 degrees (its boiling point) 21-4 per cent, in volume. On ac- 

 count of its solvent power water is never obtained pure except 

 when freshly distilled. It dissolves minerals, vegetables and 

 gases. It holds foreign matter in suspension and in solution. 

 The particles held in suspension can be filtered out. The mat- 

 ter held in solution can only be separated by evaporation. Salt 

 in water raises the temperature of the boiling and lowers that 

 of the freezing point. 



3, FUEL 



The third point to be considered is fuel. Artificial heat is 

 in the most common form derived through the combining of the 



