Another question regarding the values of atomic weights was raised very soon after their first establishment. From the somewhat inexact first determinations William Prout concluded that all atomic weights are multiples of the Prout’s assumption. atomic weight of hydrogen, thus suggesting all other elements to be probably made up from condensed hydrogen. Berzelius found his determinations not at all in accordance with this assumption, and strongly opposed the arbitrary rounding off of the numbers practised by the partisans of Prout’s hypothesis. His hypothesis remained alive, although almost every chemist who did exact atomic weight determinations, especially Stas, contradicted it severely. Even in our time it seems to have followers, who hope that in some way the existing experimental differences may disappear. But one of the most important and best-known relations, that between hydrogen and oxygen, is certainly different from the simple ratio 1 : 16, for it has been determined by a large number of different investigators and by different methods to be undoubtedly lower, namely, 1 : 15.87. Therefore, if Prout’s hypothesis contain an element of truth, by the act of condensation of some simpler substance into the present chemical elements a change of weight also must have occurred, such that the weight of the element did not remain exactly the weight of the simpler substance which changed into it. We have already remarked that such phenomena are not yet known with certainty, but they cannot be regarded as utterly impossible.

It may here be mentioned that the internationality of science has shown itself active also in the question of atomic weights. International table of atomic weights. These numbers undergo incessantly small variations because of new work done for their determination. To avoid the uncertainty arising from this inevitable state of affairs, an international committee was formed by the co-operation of the leading chemical societies all over the world, and an international table of the most probable values is issued every year. The following table is that for 1910:—

International Atomic Weights, 1910.

Name. Symbol. Atomic
Weights.
O = 16.		 Name. Symbol. Atomic
Weights.
O = 16.
Aluminium Al  27.1 Mercury Hg 200.0
Antimony Sb 120.2 Molybdenum Mo  96.0
Argon Ar  39.9 Neodymium Nd 144.3
Arsenic As  74.96 Neon Ne  20.0
Barium Ba 137.37 Nickel Ni  58.68
Beryllium Be  9.1 Nitrogen N  14.01
 (Glucinum) Gl Osmium Os 190.9
Bismuth Bi 208.0 Oxygen O  16.00
Boron B  11.0 Palladium Pd 106.7
Bromine Br  79.92 Phosphorus P  31.0
Cadmium Cd 112.40 Platinum Pt 195.0
Caesium Cs 132.81 Potassium K  39.10
Calcium Ca  40.09 Praseodymium Pr 140.6
Carbon C  12.00 Radium Ra 226.4
Cerium Ce 140.25 Rhodium Rh 102.9
Chlorine Cl  35.46 Rubidium Rb  85.45
Chromium Cr  52.0 Ruthenium Ru 101.7
Cobalt Co  58.97 Samarium Sm 150.4
Columbium Cb  93.5 Scandium Sc  44.1
 (Niobium) (Nb) Selenium Se  79.2
Copper Cu  63.57 Silicon Si  28.3
Dysprosium Dy 162.5 Silver Ag 107.88
Erbium Er 167.4 Sodium Na  23.00
Europium Eu 152.0 Strontium Sr  87.62
Fluorine F  19.0 Sulphur S  32.07
Gadolinium Gd 157.3 Tantalum Ta 181.0
Gallium Ga  69.9 Tellurium Te 127.5
Germanium Ge  72.5 Terbium Th 159.2
Gold Au 197.2 Thallium Tl 204.0
Helium He  4.0 Thorium Th 232.42
Hydrogen H  1.008 Thulium Tm 168.5
Indium In 114.8 Tin Sn 119.0
Iodine I 126.92 Titanium Ti  48.1
Iridium Ir 193.1 Tungsten W 184.0
Iron Fe  55.85 Uranium U 238.5
Krypton Kr  83.0 Vanadium V  51.2
Lanthanum La 139.0 Xenon Xe 130.7
Lead Pb 207.10 Ytterbium
Lithium Li  7.00  (Neoytterbium) Yb 172.0
Lutecium Lu 174.0 Yttrium Y  89.0
Magnesium Mg  24.32 Zinc Zn  65.37
Manganese Mn  54.93 Zirconium Zr  90.6

In the long and manifold development of the concept of the element one idea has remained prominent from the very beginning down to our times: it is the idea of a primordial matter. Since the naive statement of Thales that all Concluding remarks. things came from water, chemists could never reconcile themselves to the fact of the conservation of the elements. By an experimental investigation which extended over five centuries and more, the impossibility of transmuting one element into another—for example, lead into gold—was demonstrated in the most extended way, and nevertheless this law has so little entered the consciousness of the chemists that it is seldom explicitly stated even in carefully written text-books. On the other side the attempts to reduce the manifoldness of the actual chemical elements to one single primordial matter have never ceased, and the latest development of science seems to endorse such a view. It is therefore necessary to consider this question from a most general standpoint.

In physical science, the chemical elements may be compared with such concepts as mass, momentum, quantity of electricity, entropy and such like. While mass and entropy are determined univocally by a unit and a number, quantity of electricity has a unit, a number and a sign, for it can be positive as well as negative. Momentum has a unit, a number and a direction in space. Elements do not have a common unit as the former magnitudes, but every element has its own unit, and there is no transition from one to another. All these magnitudes underlie a law of conservation, but to a very different degree. While mass was considered as absolutely invariable in the classical mechanics, the newer theories of the electrical constitution of matter make mass dependent on the velocity of the moving electron. Momentum also is not entirely conservative because it can be changed by light-pressure. Entropy is known as constantly increasing, remaining constant only in an ideal limiting case. With chemical elements we observe the same thing as with momentum; though till recently considered as conservative, there is now experimental evidence that they do not always show this character.

Generally the laws of the conservation of mass, weight and elements are expressed as the “law of the conservation of matter.” But this expression lacks scientific exactness because the term “matter” is generally not defined exactly, and because only the above-named properties of ponderable objects do not change, while all other properties do to a greater or less extent. Considered in the most general way, we may define matter as a complex of gravitational, kinetic and chemical energies, which are found to cling together in the same space. Of these energies the capacity factors, namely, weight, mass and elements, are conservative as described, while the intensity factors, potential, velocity and affinity, may change in wide limits. To explain why we find these energies constantly combined one with another, we only have to think of a mass without gravity or a ponderable body without mass. The first could not remain on earth because every movement would carry it into infinite space, and the second would acquire infinite velocity by the slightest push and would also disappear at once. Therefore only such objects which have both mass and weight can be handled and can be objects of our knowledge. In the same way all other energies come to our knowledge only by being (at least temporarily) associated with this combination of mass and weight. This is the true meaning of the term “matter.”

In this line of ideas matter appears not at all as a primary concept, but as a complex one; there is therefore no reason to consider matter as the last term of scientific analysis of chemical facts, and the idea of a primordial matter appears as a survival from the very first beginning of European natural philosophy. The most general concept science has developed to express the variety of experience is energy, and in terms of energy (combined with number, magnitudes, time and space) all observed and observable experiences are to be described.

(W. O.)