Helium

“ The helium formations do not reach the suns limb, and it is another puzzling detail that the spectrum of the disk shows no absorption line of anything like an intensity to correspond with the emission line of helium in the chromosphere. The prominences are of two kinds, quiescent and eruptive. Some of the former are to be seen at the limb on most occasions; they may hang for days about the same place; they reach altitudes of which the average is perhaps 20,000 m., and show the spectral lines of hydrogen and helium. ”

“ The greatest dignity we may assign them is meta-element.
The formation of helium from the emanation was first shown by Ramsay and Soddy, and later confirmed by Indrikson, by Débierne, by Curie and Dewar, by Giesel and by Himstedt and Meyer. Helium, a conventional element which is devoid of any evidence of chemical affinity, is produced by or from radium, a conventional element, but the most active substance known. This occurs when the emanation is dry, and we have reason for assuming that the emanation may in reality be an active allotropic form of helium, as ozone is of oxygen. ”

“ A fact which may have a significance which we cannot at present see is that the emanation from radium gradually and spontaneously changes into helium, an alchemistical feat of nature that has opened many curious vistas to speculative thinkers. The eruptive prominences, which do not spread horizontally like the others, but ascend with marvelous velocity to elevations of half a million miles or more, are apparently composed largely of metallic vapors—i.e. metals which are usually solid on the earth, but which at solar temperatures are kept in a volatilized state. ”

“ Roughly a million volumes of air contain 20 volumes of neon and helium, about 15 of the former to 5 of the latter, approximately 1 volume of hydrogen being associated with them, so that in view of the enormous amounts of oxygen that are produced, helium can be obtained in practically any quantity directly from the atmosphere. ”

“ If we were to take elements of much greater atomic weight the residues would have high atomic weights also and these heavy atoms are not detected by the photographic plate nearly so easily as the lighter ones like helium, so that even if there were the same number of the atoms of the residue as of the helium present In the tube the helium might show on the plate while the residues did not. ”

“ In contact with the heat of fusion of hydrogen and lithium to form the gaseous stellar ash called helium, any material rocket chamber would have been scattered instantly as incandescent vapor. But space warps stood firm in their place, squeezing with an atom-crushing pressure of their own, natural only at the centers of stars. And now there was no secondary arrangement for the conversion of such power as was released into electricity. Even the helium became pure radiation that emerged in a stream. ”

“ These effects could be explained and the difficulties attendant on the view that the helium comes from an impurity of the ordinary kind avoided by some such view as the following. The evolution of helium is not due solely to the bombardment, by the cathode rays. In the atoms of the ordinary elements and especially in those of the alkali metals a process is at work analogous to that which causes the expulsion of a particles from the atoms of the ordinary radioactive elements ”

“ Weight for weight, it emits during its change an amount of energy at least one million times greater than any molecular compound known (see section 249) . In addition, it must be supposed that the rate of breaking up of the helium compound is independent of great ranges of temperature—a result never before observed in any molecular change. The helium compound in its breaking up must give rise to the peculiar radiations and also pass through the successive radio-active changes observed in radium. ”

“ In every single instance I have obtained negative results, and, as far as my experiments go, helium remains a permanent gas, and apparently much more difficult to liquefy than even hydrogen. The small quantity of the gas at my disposal, and, indeed, the extreme rarity of the minerals from which it is obtained, compelled me to carry out my investigation on a very small scale. Using a larger apparatus, and working at a much higher pressure, I could have submitted the gas to greater expansion. ”

“ There Is another possibility which It Is much more difficult to eliminate by means of physical experiments, though the chemical properties of the inert gases may be thought to make It very improbable; this is that helium can combine with a large number of elements and that these helium compounds exist as impurities In the salts of these elements and that these compounds of helium, present as impurities in soluble salts, are also soluble. ”

“ In a similar experiment, in which a very minute trace of helium had been added to the argon, there was no difficulty in detecting the helium on heating the tube. The conclusion therefore follows that no helium is present in our atmosphere.
It is, besides, exceedingly improbable that helium should be present. For, as shown by Dr. Johnstone Stoney, the rate of motion of a molecule of hydrogen is so rapid that, on finding its way to the confines of the atmosphere, it would escape, and travel through space until it found a [Pg 180] planet of sufficient attractive force to hold it. ”

“ It followed that in regions of the cosmos where the helium atoms were in process of formation owing to the grouping together of the protons and electrons, enormous amounts of heat and light would be radiated continually. This consequence of the theory enabled astrophysicists to account for the enormous temperature of the sun, maintained through thousands of millions of years in spite of incessant radiation in a frigid space. Helium atoms are in constant process of formation in the sun, and in this fact resides the source of its apparently inexhaustible supply of energy. ”

“ This conclusion could be indirectly tested by examining whether helium is produced in other substances besides radium, for example, in actinium and polonium.
The experimental determination of the origin of helium is beset with great difficulty on all sides. If the a particle is a helium atom, the total volume of helium produced in an emanation tube should be three times the initial volume of the emanation present, since the emanation in its rapid changes gives rise to three products each of which emits α particles. ”

“ The barometer pressure is only eleven pounds, which compensates for the excess of oxygen. The helium is a good indication of the radioactivity which must have produced the gas overhead, since helium is one of the ultimate products of radium disintegration. The oxygen must have come largely from the breaking up of carbon dioxide by plant life. ”

“ No attention is paid to the circumstance that the helium line is only seen in the spectrum of the solar protuberances, so that its universality in Nature remains as problematic as the primary matter itself ”

“ The helium atom (or, for that matter, the uranium atom) can on occasion masquerade in the scanty attire of the hydrogen atom. Normal helium has two planet electrons; but if one of these is lost, it becomes hydrogen-like and copies the simple hydrogen system on a different scale. It is significant that the Pickering Series appears only in the very hottest stars—in conditions likely to cause loss of an electron. The difference between hydrogen and hydrogen-like helium is firstly the difference of atomic weight; the helium nucleus is four times as massive. ”

“ If it be required to separate the helium which is often found in the gases given off by a thermal spring, they are subjected to the action of charcoal cooled with liquid air. The result is the absorption of the less volatile constituents, i.e. all except hydrogen and helium. The gaseous residue, with the addition of oxygen, is then sparked, and the water thus formed is removed together with the excess of oxygen, when helium alone remains. Or the separation may be effected by a method of fractionation as described above. ”

“ The helium atom must therefore contain inside its nucleus two negative electrons which neutralize two of these positives and serve to hold together the four positives which would otherwise fly apart under their mutual repulsions. Into that tiny nucleus of helium, then, that infinitesimal speck not as big as a pin point, even when we multiply all dimensions ten billion fold so that the diameter of the helium atom, the orbit of its two outer negatives, has become a yard, into that still almost invisible nucleus there must be packed four positive and two negative electrons. ”

“ He found that the helium ratio, i.e. the volume of helium per gram of uranous oxide, UO2, varies with the amount of thoria present; but where the latter is absent the variations are much less marked. If helium were produced in a mineral from uranium alone, and none escaped, it is obvious that the helium ratio would depend only on the age of the mineral. For minerals of about the same age, and containing no thorium, the helium ratio would be roughly constant, if no disturbing factor required consideration. ”

“ Properties.—All attempts to make helium enter into stable chemical union have hitherto proved unsuccessful. The gas is in all probability only mechanically retained in the minerals in which it is found. Jacquerod and Perrot have found that quartz-glass is freely permeable to helium below a red-heat (Compt. rend., 1904, 139, p. 789) . The effect is even perceptible at a temperature as low as 220° C. Hydrogen, and, in a much less degree, oxygen and nitrogen, will also permeate silica, but only at higher temperatures. ”

“ If the helium were the final product, the amount present in the emanation tube after a few days or weeks would be insignificant, since the product radium D intervenes, which takes 40 years to be half transformed. Since the helium cannot be the final product of the series of changes, and since all the other products are radio-active, and almost certainly of high atomic weight, it is difficult to see what position the helium atom occupies in the scheme of transformation, unless it be the α particle expelled during the successive changes. ”

“ The attribution of the Pickering series (first observed in the spectrum of Puppis) to ionized helium was the first established example of the displacement rule, and constituted one of the earliest triumphs of the Bohr theory. [11] The detection and resolution of the alternate components of that series, which fall very near to the Balmer lines of hydrogen in the spectra of the hottest stars, and the consequent derivation of the Rydberg constant for helium, [12] represents an astrophysical contribution to pure physics which is of the highest importance. ”

“ It seems from this that the emanation experiences some particular difficulty in escaping from radium which is in a vacuum.
Disengagement of Gas by the Salts of Radium. Production of Helium.—Giesel noticed that solutions of radium bromide continually give off gases. These gases are principally hydrogen and oxygen, in the same relative proportion as in water, and might, therefore, come from the decomposition of the water of the solution. But Ramsay and Soddy also showed that there always is a small quantity of helium that they detected by its spectrum in a Geissler tube. ”

“ These relations favor the hypothesis that the helium stars contain an exceptional amount of peculiarly unstable elements, and owe their high temperature to the heat set free in the gradual elimination and destruction of these substances. The energy of formation of the atoms is being slowly dissipated as radiation from the stars, but is eventually reabsorbed by the ether, and is thus restored to the material phase of its existence by the formation of new atoms. ”

“ And, as the weight of helium is one eighth of that of an equal volume of oxygen, the weight of a molecule of helium will be the eighth part of 32, or 4. Similarly, the molecular weight of argon compared with that of an atom of oxygen taken as 16 will be 40, But the question has still to be answered: Does a molecule of helium or of argon resemble a molecule of oxygen in consisting of two atoms; or does it consist of one atom or of more than two?
It is believed that when heat is put into a gas, it is expended in causing the molecules to move. ”

“ If three helium atoms could come together to form carbon, we can easily calculate how often that should happen in a star. And it turns out that it should never happen, except for one possible accident – if there happened to be an energy level at 7.82 million volts in carbon, then the three helium atoms would come together and before they came apart, would stay together a little longer on the average than they would do if there were no level at 7.82. ”

“ In a similar manner we find that the second lightest gas, helium, at a temperature of 150° C. (300° F.) , possesses a molecular velocity of 1.62 km. (1.1 miles) per second. This is less than the 2 km. (1.24 miles) per second necessary to leave the Moon’s sphere of attraction. But all helium molecules do not move at the same speed; some are faster127 and some slower than the average. Those moving at a higher rate than 2 km. (1.24 miles) per second constitute a considerable fraction of the total. ”

“ On the views outlined, we should expect the helium nucleus of charge to be built up of four protons and two electrons. The loss of mass in forming this nucleus indicates that a large amount of energy must be liberated during its formation. If this be the case, the helium nucleus must be such a stable structure that the combined energy of four or five of the swiftest α particles would be necessary to effect its disruption. ”