A United States standard gallon holds 231 cubic inches and weighs, at 62 degrees Fahrenheit, approximately 8 1 ⁄ 3 pounds.

A British Imperial gallon holds 277.42 cubic inches and weighs, at 62 degrees Fahrenheit, 10 pounds.

The above are the true weights corrected for the effect of the buoyancy of the air, or the weight in vacuo . If water is weighed in air in the ordinary way, there is a correction of about one-eighth of one per cent which is usually negligible.

[TABLE 11]
VOLUME AND WEIGHT OF DISTILLED WATER AT VARIOUS TEMPERATURES [12]
Temper-
ature
Degrees
Fahren-
heit 		Relative
Volume
Water
at 39.2°
= 1.000 		Weight
per
Cubic
Foot
Pounds 		Temper-
ature
Degrees
Fahren-
heit 		Relative
Volume
Water
at 39.2°
= 1.000 		Weight
per
Cubic
Foot
Pounds 		Temper-
ature
Degrees
Fahren-
heit 		Relative
Volume
Water
at 39.2°
= 1.000 		Weight
per
Cubic
Foot
Pounds 		Temper-
ature
Degrees
Fahren-
heit 		Relative
Volume
Water
at 39.2°
= 1.000 		Weight
per
Cubic
Foot
Pounds
32 1.000176 62.42 160 1.02337 61.00 290 1.0830 57.65 430 1.197 52.2
39.2 1.000000 62.43 170 1.02682 60.80 300 1.0890 57.33 440 1.208 51.7
40 1.000004 62.43 180 1.03047 60.58 310 1.0953 57.00 450 1.220 51.2
50 1.00027 62.42 190 1.03431 60.36 320 1.1019 56.66 460 1.232 50.7
60 1.00096 62.37 200 1.03835 60.12 330 1.1088 56.30 470 1.244 50.2
70 1.00201 62.30 210 1.04256 59.88 340 1.1160 55.94 480 1.256 49.7
80 1.00338 62.22 212 1.04343 59.83 350 1.1235 55.57 490 1.269 49.2
90 1.00504 62.11 220 1.0469 59.63 360 1.1313 55.18 500 1.283 48.7
100 1.00698 62.00 230 1.0515 59.37 370 1.1396 54.78 510 1.297 48.1
110 1.00915 61.86 240 1.0562 59.11 380 1.1483 54.36 520 1.312 47.6
120 1.01157 61.71 250 1.0611 58.83 390 1.1573 53.94 530 1.329 47.0
130 1.01420 61.55 260 1.0662 58.55 400 1.167 53.5 540 1.35 46.3
140 1.01705 61.38 270 1.0715 58.26 410 1.177 53.0 550 1.37 45.6
150 1.02011 61.20 280 1.0771 57.96 420 1.187 52.6 560 1.39 44.9

[Pg 97]

Water is but slightly compressible and for all practical purposes may be considered non-compressible. The coefficient of compressibility ranges from 0.000040 to 0.000051 per atmosphere at ordinary temperatures, this coefficient decreasing as the temperature increases.

[Table 11] gives the weight in vacuo and the relative volume of a cubic foot of distilled water at various temperatures.

The weight of water at the standard temperature being taken as 62.355 pounds per cubic foot, the pressure exerted by the column of water of any stated height, and conversely the height of any column required to produce a stated pressure, may be computed as follows:

The pressure in pounds per square foot = 62.355 × height of column in feet.

The pressure in pounds per square inch = 0.433 × height of column in feet.