Steam

—The vapor of water; the hot invisible vapor given off by water at its boiling point, this latter depending upon the pre ure. The visible white vapor termed steam, is really a collection of fine watery particles, formed by condensation of true steam. When water is evaporated within a closed space, the proce will continue up to a certain point, when the steam is said to be saturated, this signifying that no more steam can be made, unle the temperature be raised or the pre ure lowered, by permitting some of the steam to escape.; The distinguishing properties of steam are: (1) Its fluidity, (2) its mobility, (3) its elasticity, and (4) its equality of pre ure in every direction; that is, steam has a flow like water, it has a circulation within its own body, it is capable of compre ion and expansion, and when it is confined it pre es equally upon all parts of the restraining ve el. Each molecule of steam is composed of two gases which have neither taste nor color. The difference in volume between water and steam at atmospheric pre ure is as 1646 to 1; that is, a given quantity of water expanded into steam will occupy 1646 times the space it did before. This is nearly one cubic foot. and one cubic foot of steam at atmospheric pre ure weighs.038 lbs. Steam is said to be: (1) saturated when its temperature corresponds to its pre ure, (2) superheated when its temperature is above that due to its pre ure, (3) gaseous steam or steam gas when it is highly super kea ted, (4) dry when it contains no moisture. It may be either saturated or superheated, (5) wet when it contains intermingled mist or spray, its temperature‘ corresponding to its pre ure.