Water, considered from a chemical standpoint, is a compound substance consisting of hydrogen and oxygen, in the proportion of two volumes of the former gas to one volume of the latter; or by weight it is composed of two parts of hydrogen united with sixteen parts of oxygen. It should be noted that the union of these two gases is effected by chemical action and not by mechanical mixture. Pure water is transparent, inodorous and tasteless.
Under ordinary conditions water passes the liquid form only at temperatures lying between 32° F. and 212° F.; it assumes a solid form, that of ice or snow at 32° F., and it takes the form of vapor or steam at 212° F.
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. |
The temperature 62° F. is the temperature of water used in calculating the specific gravity of bodies, with respect to the gravity or density of water as a basis, or as unity.
Weight of one cubic foot of Pure Water.
| At 32° F. | = 62·418 | pounds. | |
| At 39°·1. | = 62·425 | „ | |
| At 62° | (Standard temperature) | = 62·355 | „ |
| At 212° | = 59·640 | „ |
The weight of a cubic foot of water is, it may be added, 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 48·973 pounds.