24 BULLETIN 420, U. S. DEPARTMENT OF AGRICULTURE. 
The velocity of air calculated from the Pitot-tube readings is 
99 7 V ' - = 2,253 feet a minute, and the volume of air discharged 
each minute is 2,253X1.07 = 2,410 cubic feet. The readings, how- 
ever, were taken in the discharge pipe after the air had been heated 
by passing over the hot bottles; hence the volume of cold air supplied 
should be corrected in the ratio of the absolute temperatures of the 
air at the inlet and outlet of the box, or 2?41 ?* 4 " =2,326 cu b lc feet 
. ' 517 ' 
of cold air supplied each minute. 
The time of operating was 148.5 minutes to cool to approximately 
45° F. Therefore the total amount of air supplied for cooling was 
148.5X2,326 = 345,411 cubic feet at an average temperature of 39.6° 
F. (4.2° C), or a total weight of 345,411x0.07838 = 27,069 pounds. 
The heat required to raise the temperature of this amount of 
air and perform the work of expanding the air, which was fur- 
nished by the liquid, bottles, and crates inside the box, is 
27,069x0.169(58.1-39.6+^gXl8(357,785-345,411)=84,919B. T. 
U. In other words, 34,919 B. T. U. is the amount of heat absorbed 
from the materials inside the box, and it is obvious that the heat 
given up by these materials should theoretically equal or balance the 
amount absorbed by the air. 
Following are data and calculations of the amount of heat given 
up by the liquid, glassware, and crates: 
Weight of water used in experiments 677 pounds. 
Initial temperature of water. .• 137.4° F. (58.55° C). 
Final temperature of water 45.7° F. (7.61° C). 
Difference 91.7 F. (50.94° C). 
Weight of glass 572 pounds. 
Initial temperature of glass :...'. 137.4° F. (58.55° C). 
Final temperature of glass 45.7° F. (7.61° C). 
Difference 91.7° F. (50.94° C. \. 
Weight of wood in crates 189 pounds. 
Initial temperature of wood 79.0° F. (26.11° C). 
Final temperature of wood 43.3° F. (6.28° C). 
Difference 35.7° F. (19.83° C). 
Weight of iron in crates 198 pounds. 
Initial temperature of iron 79.0° F. (26.11° C). 
Final temperature of iron 43.3° F. (6.28° C). 
Difference 35.7° F. (19.83° C). 
Average temperature of air in room 70.0° F. (21.1° C). 
Average temperature of outgoing air 58.0° F. (14.4° C). 
B. T. U. 1 extracted from water, 677 (137.4-45.7) =62,080 
B. T. U. extracted from glass, 572X0.1877 (137.4-45.7) = 9. S4S 
1 Fahrenheit degrees were used in the calculations; hence results are in B. T. U. 
