IMPORTANT PRINCIPLES RELATING TO WATER.
There are some underlying natural laws and other data relating to water which every engineer should thoroughly understand. Heat, water, steam, are the three properties with which he has first to deal.
Weight of one cubic foot of Pure Water.
| At 32° F. | = | 62.418 | pounds. | |
| At 39.1°F | = | 62.425 | „ | |
| At 62° | (Standard temperature) | = | 62.355 | „ |
| At 212° | = | 59.640 | „ |
The weight of a cubic foot of water is about 1000 ounces (exactly 998.8 ounces), at the temperature of maximum density.
The weight of a cylindrical foot of water at 62° F. is 49 lbs. (nearly). The weight of a cylindrical inch is 0.4533 oz.
There are four notable temperatures for water, namely,
| 32° F., | or | 0° C. | = the freezing point under one atmosphere. |
| 39.1° | or | 4° | = the point of maximum density. |
| 62° | or | 16°.66 | = the standard temperature. |
| 212° | or | 100° | = the boiling point, under one atmosphere. |
Water rises to the same level in the opposite arms of a recurved tube, hence water will rise in pipes as high as its source.
The pressure on any particle of water is proportioned to its depth below the surface, and as the side pressure is equal to the downward pressure.
Water at rest presses equally in all directions. This is a most remarkable property, the upward direction of the pressure of water is equal to that pressing downwards, and the side pressure is also equal.
Any quantity of water, however small, may be made to balance any quantity, however great. This is called the Hydrostatic Paradox, and is sometimes exemplified by pouring liquids into casks through long tubes inserted in the bung holes. As soon as the cask is full and the water rises in the pipe to a certain height the cask bursts with violence.
Water is practically non-elastic. A pressure has been applied of 30,000 pounds to the square inch and the contraction has been found to be less than one-twelfth.
The surface of water at rest is horizontal. A familiar example of this may be noted in the fact that the water in a battery of boilers seeks a uniform level, no matter how much the cylinders may vary in size.
A given pressure or blow impressed on any portion of a mass of water confined in a vessel is distributed equally through all parts of the mass; for example a plug forced inwards on a square inch of the surface of water, is suddenly communicated to every square inch of the vessel’s surface, however large, and to every inch of the surface of any body immersed in it.
Weight and Capacity of Different Standard Gallons of Water.
| Cubic inches in a Gallon. | Weight of a Gallon in pounds. | Gallons in a cubic foot. | Weight of a cubic foot of water, English standard, 62.221 lbs. Avoirdupois. | |
|---|---|---|---|---|
| Imperial or English | 277.264 | 10.00 | 6.232102 | |
| United States | 231. | 8.33111 | 7.480519 |