Vaporization

“ The earlier inventors often expressed the idea that an explosive mixture could be prepared without any vaporization whatever, by simply producing an atmosphere containing inflammable liquid in extremely small particles distributed throughout the air in such proportion as to allow of complete combustion. ”

“ Total Heat and Latent Heat.—To effect the conversion of a solid or liquid into a vapour without change of temperature, it is necessary to supply a certain quantity of heat. The quantity required per unit mass of the substance is termed the latent heat of vaporization. The total heat of the saturated vapour at any temperature is usually defined as the quantity of heat required to raise unit mass of the liquid from any convenient zero up to the temperature considered, and then to evaporate it at that temperature under the constant pressure of saturation. ”

“ This turbulent vaporization takes place at any temperature, even down to the freezing point, provided the pneumatic pressure be removed from the liquid by the air pump, or any other means. Ebullition always accelerates evaporation, as it serves to carry off the aqueous particles not simply from the surface, but from the whole body of the water. ”

“ Now carefully fix in the mind that a liquid does not need to be raised to its boiling point before vaporization begins, for it operates at all temperatures, even after the liquid is frozen, but much more rapidly from the liquid. ”

“ It is a matter of common experience that evaporation is accelerated by currents of air, or by the use of an exhaust pump, or by any process which removes the vapour rapidly from the liquid. On the other hand, it is retarded, and finally ceases, if the vapour is allowed to accumulate in a closed space. When this equilibrium state is reached, the space is said to be saturated with the vapour; the density of the vapour is then the maximum which can exist in the presence of the liquid at the temperature of the experiment, and its pressure is called the saturation-pressure. ”

“ The saturation-pressure invariably increases rapidly with rise of temperature, according to a regular law which has been the subject of many elaborate investigations. When the vapour-pressure of a liquid becomes equal to the external pressure, bubbles of vapour are freely formed in the interior of the liquid by the familiar process of boiling or ebullition. ”

“ In common language a vapour is a gaseous or elastic fluid, which emanates or evaporates from the surface of a solid or liquid at temperatures below its boiling-point. A volatile liquid or solid is one which evaporates rapidly at ordinary temperatures. ”

“ Since the specific heat of the liquid increases rapidly at high temperatures, while dH/dO diminishes, it is clear that the latent heat must diminish more and more rapidly as the critical point, is approached. ”

“ Water, flowing over a bed of this mineral, liberates the gas in the form of an almost invisible vapor. It is swept forward in a cloud by the wind, some of it is carried along above the course of the underground stream, and as soon as it reaches an opening in the earth, like a fissure crack in the rock or ground, the gas rises and whoever breathes it dies or is rendered unconscious for a time, according to the strength of the vapor. ”

“ I have repeated this experiment often. The elements of the water dissociate by the heat, and instantaneously recombine in cooling, causing the detonation."
The degree of dissociation, as of evaporation, depends on the pressure: under four atmospheres (60 lbs.) , the heat required for dissociation is 1,870° . But the question arises, If the vapor dissociates at these temperatures, why do not the gases instantaneously combine and detonate? The reason is plain: in the boiler the atoms at once become mixed with a volume of steam sufficient to render them inexplosive. ”

“ Thus fire has a double fund of certain subsistence; if it consume much air it can also produce much by the rarefaction of water, and thus repair, in the mass of atmosphere, all the quantity it destroyed, while ulteriorly it converts itself with air into fixed matter in the terrestrial substances which it penetrates by its heat or by its light. And so, likewise, as water is converted into air, or into vapours, as volatile as air, by its rarefaction, it is also converted into a solid substance by a kind of condensation. Every fluid is rarefied by heat and condensed by cold. ”

“ According to a law of MM. Clement and Desormes, a law established by direct experiment, the vapor of water, under whatever pressure it may be formed, contains always, at equal weights, the same quantity of heat; which leads to the assertion that steam, compressed or expanded mechanically without loss of heat, will always be found in a saturated state if it was so produced in the first place. The vapor of water so made may then be regarded as a permanent gas, and should observe all the laws of one. ”

“ If we suppose a sea of melted matter to exist beneath the crust of the earth, we should have analogous effects whenever hydrated rocks, broken off from the shell, fall into the ignited masses.
The theory of the agency of vapor is also supported by the rumblings and subterranean thunders which sometimes continue for months and even for years without being attended by shocks, and for which it is difficult to imagine any other causes than sudden condensation, or a flow of gaseous matter at very high tension through a narrow orifice. ”

“ There remained but one alternative, to pass through the thick mists of the vapor-layer itself, but that, though concealing us from the guns of air-forts above and beneath, would be in itself suicide, since such vapor-layers between the forts were invariably filled in war-time with floating air-mines, great cube-like metal containers held aloft and motionless by their own electrostatic-motors and tube-propellers and which contained a terrific heat-charge which was instantly released upon any luckless ship that touched them. ”

“ The most abundant of the substances which are ejected from volcanoes is steam or water-gas, which, as we have seen, issues in prodigious quantities during every eruption. But with the steam a great number of other volatile materials frequently make their appearance. The chief among these are the add gases known as hydrochloric acid, sulphurous acid, sulphuretted hydrogen, carbonic add, and boracic acid; and with these acid gases there issue hydrogen, nitrogen, ammonia, the volatile metals arsenic, antimony, and mercury, and some other substances. ”

“ Within the boiler this steam is transparent and invisible; but to keep it in this invisible state a heat would be required as great as that within the boiler. When the vapor mingles with the cold air above the hot funnel, it ceases to be vapor. Every bit of steam shrinks, when chilled, to a much more minute particle of water. The liquid particles thus produced form a kind of water dust of exceeding fineness, which floats in the air, and is called a cloud.
[Pg 204] Watch the cloud banner from the funnel of a running locomotive: you see it growing gradually less dense. ”

“ The Sun said “Yes,” and took ever so many other drops, too, so that Aqua might not be lonesome on the way. He did not know this, however, for they all had been changed into fine mist or vapor. Do you know what vapor is? If you breathe into the air, when it is cold enough, you will see it coming out of your mouth like steam, and you may also see very hot steam coming from the nose of a kettle of boiling water. When it is quite near to the earth, where we can see it, we call it “fog.” ”

“ As their phenomena of color show that they are not water vapor alone, it is a fair conclusion that they are made up of a mixture of dust and water vapor, such as occurs in our chimney smoke. Our ordinary coal smoke is always composed in large part of steam, in which the little bits of carbon are mingled, as the soot is in the London fog. When dust of any kind becomes entangled in water vapor, the union is of a singularly permanent nature, the two being unwilling to separate until they fall as rain. ”

“ Moreover, the amount of water vapor given off during the combustion of gas is greater than in the case of the other illuminants. Water vapor having a great power of absorbing radiant heat from the burning gas becomes heated, and diffusing itself about the room, causes great feeling of oppression; the air also being highly charged with moisture, is unable to take up so rapidly the water vapor which is always evaporating from the surface of our skin, whereby the functions of the body receive a slight check, resulting in a feeling of malaise. ”

“ Only Water Vapor Protects the Earth from Death by Freezing. In Chapter IV you are told that the earth is surrounded by four atmospheres that conduct themselves each quite independently of the others, and that water vapor (aqueous vapor) is one of them. Water vapor plays the most important part in absorbing incoming rays and in absorbing and reflecting back outgoing heat rays from the earth. Without the vaporous atmosphere the sun’s rays would be but slightly absorbed as they entered and radiation from the earth would readily escape through the atmosphere to outer space. ”

“ The vapor which is thus condensed in the air has all been obtained by the evaporation of the water on the earth’s surface. It rises with the warm air, which losing its heat as it ascends, and coming too in contact with colder layers of the atmosphere, can not hold all its vapor, and is obliged to get rid of the excess, which then condenses into cloud.
On a summer morning the sky is often free from cloud. As the day advances, and the earth gets warmed, more vapor is raised ”

“ When in every vessel of heated water mankind had always seen a vapor arise, who could have supposed that in this simple fact, nature had furnished an agent, which by skilfully managing, he could multiply his natural strength a thousand fold, and move from place to place with the swiftness of a bird? By the alternate production and condensation of this vapor, which he is able to do by the very common agents of fire and water, he is able to extract the ponderous minerals from the bowels of the earth, having made it previously drain off the water which put them out of his reach. ”

“ As the smoke and vapour which ascend from burning fuel rise in consequence of their being rarefied by heat, and made lighter than the air of the surrounding atmosphere; and as the degree of their rarefaction, and consequently their tendency to rise, is in proportion to the intensity of their heat; and further, as they are hotter near the fire than at a greater distance from it, it is clear that the nearer the throat of a Chimney is to the fire, the stronger will be, what is commonly called, its DRAUGHT, and the less danger there will be of its smoking. ”

“ If a cloud of vapor is made in a house and cannot get out, let as see what happens. The vapor from boiling water is very warm. The glass window is colder. The vapor gathers on the glass in a mist of tiny drops. The little drops roil together into big drops.
These get so heavy that they roll down the glass. They roll down the walls, too, and drop from the ceiling. If vapor is not turned out of doors it makes a room damp. That is just what happens when it rains. The vapor in the air goes up into the sky. When it finds a cold layer of air it rolls into large drops and falls. ”

“ The liquid is volatile, and its vapor is usually inhaled by the patient. Let a quantity of this vapor be introduced into a wide glass tube, and let a concentrated beam of solar light be sent through the tube along its axis. Prior to the entry of the beam, the vapor is as invisible as the purest air. When the light enters, a bright cloud is immediately precipitated on the beam. This is entirely due to the waves of light, which wreck the nitrite of amyl molecules, the products of decomposition forming innumerable liquid particles which constitute the cloud. ”

“ Vaporizing is conducted in the interior of the combustion chamber, which is so arranged that the heat of each explosion maintains it at a temperature sufficiently high to enable the oil to be vaporized by mere injection upon the hot surfaces. The vaporizer A is heated up by a separate lamp, the oil is injected at the oil inlet B, and the engine is rotated by hand. The piston then takes in a charge of air by the air-inlet valve into the cylinder, the air passing by the port directly into the cylinder without passing through the vaporizer chamber. ”

“ I. The first difference is, that heat is an expansive motion, by which the body strives to dilate itself, and to occupy a greater space than before. This difference is principally seen in flame, where the smoke or thick vapor is clearly dilated and bursts into flame. It is also shown in all boiling liquids, which swell, rise, and boil up to the sight, and the process of expansion is urged forward till they are converted into a much more extended and dilated body than the liquid itself, such as steam, smoke, or air. ”

“ A million horses would barely have standing-room on a square mile. Considerations like this show that we can account for the most violent hurricanes by the energy set free by the mere condensation of vapor required for the concomitant rain. Now, the modern kinetic theory of gases shows that the particles of water vapor are so small that there are somewhere about three hundred millions of millions of them in a single cubic inch of saturated steam at ordinary atmospheric pressure. ”

“ By means of the fan-like action resulting from the rotation of the sun, the vapors dissociated in space to-day would be drawn toward the polar surfaces of the sun to-morrow, be heated by increase in density, and would burst into flame at a point where both their density and temperature had reached the necessary elevation to induce combustion, each complete cycle taking, however, years to be accomplished. The resulting aqueous vapor, carbonic acid, and carbonic oxide would be drawn toward the equatorial regions, and be then again projected into space by centrifugal force. ”