An Attempt Towards A Chemical Conception Of The Aether

So long as the law remained unconfirmed, it was not possible to extrapolate (i.e., to determine points beyond the limits of the known) by its means, but now such a method may be followed, and I have ventured to do so in the following remarks on the ether, as an element lighter than hydrogen. My reason for doing this was determined by two considerations. In the first place, I think I have not many years for delay; and, in the second place, in recent years there has been much talk about the division of atoms into more minute electrons, and it seems to me that such ideas are not so much metaphysical as metachemical, proceeding form the absence of any definite notions upon the chemism of ether, and it is my desire to replace such vague ideas by a more real notion of the chemical nature of the ether.

For until some one demonstrates either the actual transformation of ordinary matter into ether, or the reverse, or else the transformation of one element into another, I consider that any conception of the division of atoms is contrary to the scientific teaching of the present day; and that those phenomena in which a division of atoms is recognized would be better understood as a separation or emission of the generally recognized and all-permeating ether. In a word, it seems to me that the time has arrived to speak of the chemical nature of the ether, all the more so since, so far as I know, no one has spoken at all definitely on this subject.

When I applied the periodic law to the analogs of boron, aluminum, and silicon, I was 33 years younger than now, and I was perfectly confident that sooner or later my prediction would be fulfilled. Now I see less clearly and my confidence is not so great. Then I risked nothing, now I do. This required some courage, which I acquired when I saw the phenomena of radioactivity. I the saw that I must not delay, that perhaps my imperfect thoughts might lead some one to a surer path than that which was opened to my enfeebled vision.

First, I will treat of the position of helium, argon, and their analogs in the periodic system; then of the position of ether I this system; and conclude with some remarks on the probable properties of ether according to the position it occupies in the periodic system.

When, in 1895, I first heard of argon and its great chemical inertness, I doubted the elementary nature of the gas, and thought it might be a polymeride of nitrogen, N₃, just as ozone, O₃, is a polymeride of oxygen, with the difference that, while ozone is formed from oxygen with the absorption of heat, argon might be regarded as nitrogen deprived of heat. In chemistry nitrogen was always regarded as the type of chemical inertness, i.e., of an element which enters into reaction with great difficulty, and if its atoms lost heat in becoming condensed by polymerization from N₂to N₃, it would form a still less active body; just as silica, which is formed from silicon and oxygen with the evolution of heat, is more inert than either of them separately.

Berthelot subsequently published a similar view on the nature of argon, but I have now long discarded that and consider argon to be an independent element, as Ramsay held it to be from the very beginning. Many reasons induced me to adopt this view, and chiefly the facts that (1) the density of argon is certainly much below 21, namely about 19, that of H being 1, while the density of N₃ would be about 21, for the molecular density of N₃ = 14 x 3 = 42 and the density would be half this; (2) helium, discovered by Ramsay in 1895, has a density of about 2 referred to hydrogen, and exhibits the same chemical inactivity as argon, and in its case this inactivity can certainly not be due to a complexity of its molecule; (3) in their newly discovered neon, krypton, and xenon,

Ramsay and Travers found a similar inactivity which, in these cases also, could not be explained by polymerization; (4) the independent nature of the separate spectra of these gases, and the invariability of these spectra under the influence of electric sparks, proved that they belong to a family of elementary gases different from all other elements, and (5) the graduation and definite character of the physical properties in dependence upon the density and atomic weight further confirm the fact of their being simple bodies, whose individuality, in the absence of chemical reactions, can only be affirmed from the constancy of their physical features. An instance of this is seen in the boiling points (at 760 mm) or temperatures at which the vapor pressures equal the atmospheric pressure and at which the liquid and gaseous phases are co-existent:

                                        He        Ne      Ar         Kr         Xe 
Atomic weight:                  4         19.9     38         81.8     128 
Observed density:             2         9.95     18.8      40.6     63.5 
Observed boiling point:     -262     -239    -187     -152     -100

This recalls the halogen group:

                               F         Cl         Br         I 
Mol. Weight:           38       79.9     159.9     254 
Vapor density:         19       35.5     80         127 
Boiling point            -187    -34     +57.7     +183.7

In both cases the boiling point clearly rises with the atomic or molecular weight. When the elementary nature of the argon analogs and their characteristic chemical inactivity were once proved, it became essential that they should take their place in the periodic system of the elements; not in any of the known groups but in a special one of their own, for they exhibited new, hitherto unknown chemical properties, and the periodic system embraces in different groups those elements which are analogous in their fundamental chemical properties, although not in dependenceupon these properties but upon their atomic weight, which apparently — previous to the discovery of the periodic law — stands in no direct relation to these properties.

This was a critical test for the periodic law and the analogs of argon, but they both stood the test with perfect success; that is, the atomic weights, calculated from the observed densities, proved to be in perfect accordance with the periodic law.

Although I assume that the reader is acquainted with the periodic law, yet it may be well to mention that if the elements be arranged in the order of their atomic weights it will be found that similar variations in their chemical properties repeat themselves periodically, and that the order of the faculty of the elements to combine with other elements also corresponds with the order of their atomic weights. This is seen in the following simple example.

All the elements having an atomic weight of not less than 7 and not more than 85.5 fall into two series:

Li = 7.0  ~  Be = 9.1  ~  B = 11.0  ~  C = 12.0  ~  N = 14.0  ~  O = 16  ~  F = 19.0 ~ 
Na = 23.0  ~  Mg = 24.3  ~  Al = 27.0  ~  Si = 28.4  ~  P = 31.0  ~  S = 32.1  ~  Cl = 35.5

Each pair of elements present a great similarity in their chief properties; this is especially marked in the higher saline oxides, which in the lower series are:

Na₂O ~ MgO ~ Al₂O3 ~ SiO₂ ~ P₂O₅ ~ SO₃ ~ Cl₂O₇, or 
Na₂O, Mg₂O₂, Al₂O₃, Si₂O₄, P₂O₅, S₂O₆, Cl₂O₇.

Thus the atomic order of the elements exactly corresponds to the arithmetical order from 1 to 7. So that the groups of the analogous elements may be designated by the Roman ciphers I to VII: and when it is said that phosphorus belongs to Group V, it signifies that it forms a higher saline oxide P₂O₅. And if the analogs of argon do not form any compounds of any kind, it is evident that they cannot be included in any of the groups of the previously known elements, but should form a special zero group which at once expresses the fact of their chemical indifference. Moreover, their atomic weight should necessarily be less than those of group I: Li, Na, K, Rd, and Cs, but greater than those of the halogens, F, Cl, Br and I, and this a priori conclusion was subsequently confirmed by fact, thus:

Halogens         Argon analogs     Alkali metals 
                       He = 4.0              Li = 7.03 
F = 19            Ne = 19.9            Na = 23.05 
Cl = 35.5        Ar = 38                K = 39.1 
Br = 79.95      Kr = 81.8            Rh = 85.4 
I = 127            Xe = 128            Cs = 132.9

The five well-known alkali metals correspond to the newly discovered argon analogs, and the atomic weights of both exhibit the same common law of periodicity. But the halogens and alkali metals are the most chemically active among the elements, and are, moreover, of opposite chemical nature, the first being particularly prone to react with metals and the others with metalloids, the former appearing at the anode and the latter at the cathode. They must therefore stand at the two extremes of the periodic system, as in the scheme in Figure 1.

Figure 1

Although this arrangement best expresses the periodic law, the distribution of the elements according to groups and series in the table of Figure 2 is perhaps clearer:

Figure 2

Here x and y stand for two unknown elements having atomic weights less than that of hydrogen, whose discovery I now look for.

A reference to the above remarks on the argon group of elements shows first of all that such a zero group as they correspond to could not possibly have been foreseen under the conditions of chemical knowledge at the time of the discovery of the periodic law in 1869; and, although I had a vague notion that hydrogen might be preceded by some elements of less atomic weight, I dared not put forward such a proposal, because it was purely conjectural, and I feared to injure the first impression of the periodic law by its introduction. Moreover, in those days the question of the ether did not awaken much interest, for electrical phenomena were not then ascribed to its agency, and it is this that now gives such importance to the Aether.