Absorption line

“ Thus closely do the absorptions in the two cases run together—thus emphatically do the molecules assert their individuality. As long as their number is unaltered, their action on radiant heat is unchanged. Passing from the lime light to the incandescent spiral, the absorptions of the smaller equivalent quantities, in the two tubes, were 23.5 and 23.4 per cent.; while the absorptions of the larger equivalent quantities were 32.1 and 32.6 per cent., respectively. This constancy of absorption, when the density of a gas or vapor is varied, I have called "the conservation of molecular action." ”

“ The preceding tabulation summarizes the present state of the observational material bearing on the positions of the maxima of absorption lines. The comparison with theory is an important and difficult problem. The theoretical formulae contain as variables the temperature and the pressure; and the [Pg 131] fractional concentration, , is very sensitive to changes in both these variables. ”

“ The method consists in comparing the intensity after transmission through a layer of known thickness of the absorbent with the intensity of light from the same source which has not passed through the medium, k being thus obtained for various thicknesses and found to be constant. In the case of solutions, if the absorption of the solvent is negligible, the effect of increasing the concentration of the absorbing solute is the same as that of increasing the thickness in the same ratio. ”

“ Such experiments, recently verified, entirely dispose of the hypothesis that liquid films were the cause of the observed absorption.
The vapor-hesion hypothesis involves the assumption that liquids exert on radiant heat an absorbent power which is denied to their vapors. It assumes, in other words, that the seat of absorption is the molecule considered as a whole, and not the constituent atoms of the molecule. For, were the absorption intra-molecular, the passage from the liquid to the vaporous condition, which leaves the molecules intact, could not abolish the absorption. ”

“ The Decomposition of any remaining Portion, and the adoption of measures best calculated to obviate its absorption. Where the substance is in a solid form, and acts by absorption, we should be very cautious how we favour its solution; while, if it exists in a liquid state, our object must be to render its active portion insoluble; this problem involves a series of questions which are wholly chemical. In order to prevent, or retard, the absorption of the active matter, we must, to a great degree, depend upon the agency of vital adjuvants ”

“ Because calculation of the absorbance area involves many points in the sample spectrum, Equation C3 leads to much more accurate results than the single-point calculation represented by Equation C2.
However, when many absorbing compounds are present in a sample, the absorption patterns of the various compounds often overlap. In this case, there is usually not an isolated analytical region for each compound in which only that compound absorbs infrared radiation; no single absorbance point and no simple absorbance area is suitable for determining any of the component concentrations. ”

“ Repeated tests have shown that 5.5 kilograms of sulphuric acid will remove the water-vapor from a current of air passing through the absorbers at the rate of 75 liters of air per minute, without letting any appreciable amount pass by until 500 grams of water have been absorbed. At this degree of saturation a small persistent amount of moisture escapes absorption in the acid and consequently a second absorber will begin to gain in weight. Experiments demonstrate that the first vessel can gain 1,500 grams of water before the second gains 5 grams. ”

“ Thus, when a gas is absorbed by water, much heat is evolved, and we may suppose the result to be due in part to chemical combination, and in part to the condensation of the gas into a liquid, by which means its latent heat is rendered sensible. On the other hand, when a liquid unites with a solid, or when two solids unite with one another, and the product is a liquid, we have very often the absorption of heat, the heat rendered latent by the dissolution of the solid being more than that generated by combination. ”

“ Analytical operations can often be performed still more conveniently with the help of charcoal, taking advantage of the selective character of its absorption, the general law of which is that the more volatile the gas the less is it absorbed at a given temperature. ”

“ There are two ways in which light can be absorbed. In one the atom absorbs so greedily that it bursts, and the electron scurries off with the surplus energy. That is the process of ionization which was shown in Fig. 5. Clearly this cannot be the process of absorption in the chromosphere because, as we have seen, the atom cannot afford to lose the electron. ”

“ The case for the percolation of water and the absorption of the gas is made of conical shape, with the largest diameter at the bottom, to produce the greatest absorption of the heavy gas when first admitted; while horizontal partitions, or shelves, in said case are provided with upwardly projecting tubes which hold a permanent surface of water on the said partition or shelves. ”

“ He subsequently examined the passage of gases through septa or partitions of india-rubber, unglazed earthenware and plates of metals such as palladium, and proved that gases pass through these septa neither by diffusion nor effusion nor by transpiration, but in virtue of a selective absorption which the septa appear to exert on the gases in contact with them. By this means (“atmolysis”) he was enabled partially to separate oxygen from air. ”

“ If the mixture of gas contains any muriatic or sulphurous acid gas, a rapid and considerable absorption will instantly take place, from the strong tendency these two gasses have, especially the former, to combine with, or be absorbed by water. If the water only produces a slight absorption of gas hardly equal to its own bulk, we conclude, that the mixture neither contains muriatic acid, sulphuric acid, or ammoniacal gas, but that it contains carbonic acid gas, of which water only absorbs about its own bulk. ”

“ Absorption of Gases by Solids and Liquids.—If a piece of heated charcoal is placed in a test-tube containing ammonia gas, inverted in mercury, the ammonia is seen to disappear, the mercury rising to take its place. The ammonia has been absorbed by the charcoal, the gas molecules clinging closely to the solid. The charcoal being very porous presents a large surface to the action of the gas. ”

“ These are: absorptive activity, absorptive capacity, versatility, mechanical strength, chemical stability, low breathing resistance, ease of manufacture and availability of raw materials.
Absorptive activity, or a very high rate of absorption, is one of the more important properties of a satisfactory absorbent. A normal man when exercising violently breathes about 60 liters of air per minute, and since inhalation occupies but slightly more than half of the breathing cycle, the actual rate at which gas passes through the canister during inhalation is about 100 liters per minute. ”

“ In the course of an hour there is ordinarily removed from the chamber not far from 25 grams of water-vapor and 20 to 30 grams of carbon dioxide. This necessitates weighing the absorbers to within 0.25 gram if an accuracy of 1 per cent is desired. The sulphuric-acid absorbers weigh about 18 kilograms when filled with acid. In order to weigh this receptacle so as to measure accurately the increase in weight due to the absorption of water to within less than 1 per cent, we use the balance shown in fig. ”

“ It is this principle that is utilized in refrigeration and ice making. In the absorption system, where aqua ammonia is used, the liquor is contained in a retort to which heat is applied by means of a steam coil, and a great part of the gas which was held in solution by the water is expelled, and carries with it a small amount of water or vapor. This passes into a separator in the top of a condenser, from which the water returns again to the retort, the ammonia gas, under considerable pressure, passing into the coolers. These are large receptacles in which the gas is permitted to expand. ”

“ The carbon dioxid remaining in the bottle is driven out by a stream of dry, pure air. The air is allowed to pass through the apparatus for about ten hours. The carbon dioxid driven out is collected in an absorption apparatus and weighed. The absorption apparatus should consist of a series of Geissler potash absorption bulbs and finally a ᥩ form soda-lime tube. In front of the absorption apparatus is placed a drying bulb containing sulfuric acid. Inasmuch as the temperature and pressure can be readily determined, the weight of carbon dioxid obtained is easily calculated to volume. ”

“ Attention has been called to the fact that both oxygen and nitrogen can be obtained in the liquid state by strongly cooling the gases and applying great pressure to them. Since air is largely a mixture of these two gases, it can be liquefied by the same methods.
The methods for liquefying air have been simplified greatly in that the low temperature required is obtained by allowing a portion of the compressed air to expand. The expansion of a gas is always attended by the absorption of heat. ”

“ No sufficient advantage is attained by raising the pressure of the gases above atmosphere, but a capacious vessel is necessary. This may consist of a glass sphere of 50 litres’ capacity, into the neck of which, presented downwards, the necessary tubes are fitted. The whole of the interior surface is washed with a fountain of alkali, kept in circulation by means of a small centrifugal pump. In this apparatus, and with about one horse-power utilized at the transformer, the absorption of gas is 21 litres per hour (“The Oxidation of Nitrogen Gas,” Trans. Chem. Soc., 1897) . ”

“ For the various parts of the absorber system we have relied upon the original type of couplings used in the earlier apparatus. A rubber gasket is placed between the male and female part of the coupling and the closure can be made very tight. In fact, after the absorbers are coupled in place they are invariably subjected to severe tests to prove tightness.
For connecting the piping between the calorimeter and the absorption system we use ordinary one-inch hose-couplings, firmly set up by means of a wrench and disturbed only when necessary to change from one calorimeter chamber to another. ”

“ The absorption apparatus may be a ten-bulbed absorption tube or any convenient form of absorption bulbs which subject the gas to intimate contact with the solution. If acetylene from a service-pipe is to be tested, it is led direct from the nozzle of a gas- tap to the absorption tube, the outlet of which is connected with an aspirator or the inlet of an experimental meter, by which the volume of gas passed through the solution is measured. ”

“ In the silvered experimental tube, which, as stated, is 38 inches long, hydride of amyl vapor, at a mercury pressure of 6·6 inches, is equivalent to a liquid layer one millimetre in thickness, while a vapor column of sulphuric ether, of the same length, and 7·2 inches pressure, would also produce a liquid layer one millimetre thick. The experiment has been made with the utmost care, both with the lime-light and the incandescent platinum, with the result that it is impossible to say that there is any difference between the vapor absorption and the liquid absorption. ”

“ Limiting in the first place our enquiries to the phenomena of absorption, we have to picture a succession of waves issuing from a radiant source and passing through a gas; some of them striking against the gaseous molecules and yielding up their motion to the latter; others gliding round the molecules, or passing through the intermolecular spaces without apparent hindrance. The problem before us is to determine whether such free molecules have any power whatever to stop the waves of heat ”

“ DIFFERENCES OF ABSORPTION BY GASES.
This exclusion of one of the three states of material aggregation from the region of experiment was, however, by no means satisfactory; for our right to infer, from the [Pg 244] deportment of a solid or a liquid towards radiant heat, the deportment of a gas, is by no means evident. In both liquids and solids we have the molecules closely packed, and more or less chained by the force of cohesion; in gases, on the contrary, they are perfectly free, and widely separated. ”

“ But the long series of reactions, represented by the deportment of nitrite of amyl vapor, does not favor this conception; for, were the atoms animated solely by a common motion, the molecules would not be decomposed. The fact of decomposition, then, goes to prove the atoms to be the seat of the absorption. They, in great part, take up the energy of the ether-waves, whereby their union is severed, and the building materials of the molecules are scattered abroad. ”

“ The question could not be settled by experiments made at the same temperature, and if the temperature is altered the question is complicated by the distinction which would probably have to be drawn between the number of collisions and their intensity. Experimentally we should be confined to a strict investigation of absorption spectra, because in the electric discharge temperature has no definite meaning, and variations of pressure and density are not easily measured. ”