4i6 



NA TURE 



[February 3, 1910 



which, while it does not supersede the periodic scheme, 

 would, if it could be recognised, supplement it. 



From a consideration of tile almost unbroken sequence 

 in the atomic weights of the known elements, it seems 

 probable, that few additional elements are to be expected, 

 except possibly one following Mo and another following 

 \V, save in the. region from Bi to Ra. This suggests the 

 nniark that, after all, it is not necessary to assume that 

 ihc materials of which the earth consists should neces- 

 sarily include a sample of every possible element indicated 

 bv such a scheme. Some which are missing from terres- 

 trial., matters may perhaps be responsible for phenomena 

 recognisable by the spectroscope in stars or nebula; far 

 distant in cosmical space. The unexpected, however, often 

 happens, and, remembering the discovery of terrestrial 

 helium, it is permissible to hope that some of the vacant 

 spaces may hereafter be filled by earthly occupants. 



There is one important point to be noted here, namely, 

 that if the so-called rare earth metals, praseodymium, 

 neodymium, samarium, gadolinium, terbium, dysprosium, 

 erbium, ytterbium, and others of which the existence is 

 doubtful, do lie in the position indicated, the original 

 statement of the periodic law breaks down at this point. 



One result of the recognition of the periodic law is that 

 theories concerning the genesis of the elements have re- 

 ceived a stimulus previously unknown. It is, however, 

 interesting to note the attitude of Mendelifeff toward this 

 question, and the small extent to which this attitude 

 appears to have become modified with the lapse of time. 

 When, in i88q, twenty years after the discovcrv of the 

 law, he composed the Faraday lecture, he seems' to have 

 regarded speculation in this direction as a kind of abuse 

 of the periodic system. 



Fifteen years later, after the discovery of the argon 

 group of elements, of the phenomena of radio-activity, and 

 of radium, it became necessary to consider the relations 

 of these substances to the periodic scheme. In a remark- 

 able article contributed to the new Russian Encyclopa;dia, 

 and subsequently printed as Appendix iii. to the " Prin- 

 ciples " (English edition, iqos), Mendel6eff gives a new 

 table of the elements, in which places are found, not onlv 

 for the argon group and radium, but for two hvpothetical 

 elements, which are placed before helium and 'designated 

 X and y. 



The y in the table is supposed to be an analogue of 

 helium, and m.iy be identified hereafter with "coronium," 

 which has been recognised in the sun's coronal atmosphere. 

 This gas would have, according to Mendel^efT, a density 

 about 0-2, and therefore a molecular weight about 0-4, or 

 about one-tenth that of helium. 



X is the "ether" of the physicist, for which Mendel^eff, 

 disregarding conventional views, supposes a molecular 

 structure. He also assumes that, like the argon group, this 

 element is chemically inert and possesses a very low 

 density and atomic weight, estimated at 0000,000,000,053. 



Chemists and physicists have, however, found it 

 mipossible to resist the fascination of this problem, and 

 accordingly there have been nianv hvpotheses as to the 

 origin of the elements and the nature' of their connection 

 with one another. These seem to be inseparable from the 

 periodic scheme itself, which at once provokes the inquiry. 

 Why do these numerical relations occur, and what is the 

 meaning of them if they do not point to a common genesis 

 or the operation of some process of evolution? 



Hypotheses concerning the evolution of the elements 

 have hitherto bi-en usually based on the assumption that 

 the successive stages of condensation of elemental matter 

 proceeded from a single primary stuff, which by a process 

 analogous to polymerisation among carbon 'compounds 

 gave rise to atoms of greater and greater mass, which 

 were stable at the prevailing and any lower temperature. 

 The physical cause of the successive condensations is sup- 

 posed to be a falling temperature. It is, of course, possible 

 to, imagine th.at if to the stuff of which hvdrogen atoms 

 consist are added successive portions of matt'er of the same 

 kind, stable structures may at intervals result which we 

 know as the atoms of the elements helium, lithium, 

 beryllium, boron, carbon, nitrogen, oxygen, and fluorine, 

 provided the idea of internal structure in these atoms is 

 allowed. Otherwise, from the mere accretion of m.atter 

 upon a central nucleus, ther-^ seems no suflirient reason 

 NO. 2IOT, VOL. 82] 



why there should not have been formed an indefinite 

 number of intermediate masses corresponding to an in- 

 definite number of what would be called elements. 

 Further, it is difiicult to understand why simple increase 

 of mass should change, say, o.xygen into fluorine, while' 

 a further addition of the same kind should change negative, 

 fluorine into inert neon or positive sodium. The possi- 

 bility of the condensation of a single " protyl " so as to 

 produce, at successive though unequal stages of cooling, 

 the elements known to the chemist, has been most ably 

 discussed long ago by Sir William Crookes. 



This hypothesis, however, was put forward long before 

 the work of Sir J. J. Thomson and his school was given 

 to the world and the electron was accepted as a physical 

 • reality. The hypothesis that one elemental stuff may give 

 rise to the whole array of known elements by a process 

 of condensation accompanied by a loss or gain of electrons, 

 the mass of which is approximately one-thousandth of the 

 mass of an atom of hydrogen, forms the subject of a' 

 paper by Mr. \. C. G. Egerton in a recent number of our; 

 Transactions (1909, xcv., 239). The atomic weights; 

 calculated by his formula agree closely with the experi-i 

 mental atomic weights of the first fifteen elements, but the; 

 hypothesis gives no explanation of the facts observed in- 

 the physical properties of the elements arranged according- 

 to the Mendeleeff scheme, their alternation of odd and- 

 evcn valency, the transition from positive on one side of 

 the table to negative on the other, the periodicity of 

 properties shown by the sudden change of character in 

 passing from fluorine to the next element, whether it \v 

 neon or sodium. 



Another paper by Messrs. \. C. and k. E. Jessup (Phil. 

 Mng., 1908 [vi.], XV., 21) has recently provided a hypo- 

 thesis of an entirely different character. From a study of 

 the spectra of the nebula;, these authors have been led 

 to assume the existence of two hitherto unrecognised 

 elements, to which the names protoglucinum and prolo- 

 boron are assigned. These with hydrogen and helium are 

 supposed to represent four initial substances, or protons, 

 which, by condensation directly or indirectly, give rise to- 

 all the rest of the elements. The arguments of these- 

 authors are ingenious, but rather artificial in view of the 

 fact that the number of groups in the periodic ■ scheme to' 

 be provided for is greater than four. 



In the Mendeleeff chart of the elements theie is nothing 

 more striking than the gathering of the negative elements 

 toward what may be called the N.E., and the segregation 

 of the positive elements toward the S.W., the centre of 

 the intermediate territory being occupied by elements 

 which play a more or less undecided part. I have else- 

 where (Presidential .-\ddress, 1905, Trans., Ixxxvii., 564)- 

 directed attention to the fact that carbon, at any rate, is. 

 not directly deposited by electrolysis from any of its com- 

 pounds, with positive hydrogen on the one hand, or 

 negative chlorine on the other. I believe the same is true 

 of silicon, these two elements standing in a middle posi- 

 tion between the extremes occupied by lithium and fluorine 

 resoectively. 



If we assume that atoms are made up of two parts 

 (protyls), positive and negative, in proportions, which deter- 

 mine by the preponderance of one or the other whether the 

 element shall exhibit the oositive character of a metal like 

 lithium or the negative character of a halogen, we arrive 

 at a hypothesis which recalls the ideas put forward nearly 

 a century ago by Berzelius. His views are familiar to- 

 every student of the history of chemistry, but have long 

 been relegated to the lumber-room of worn-out doctrine. 

 The last few years have, however, given us the remark- 

 able experimental investigations of J. J. Thomson already 

 referred to, and the new conceptions concerning the nature 

 of atoms, which revive the fundamental idea that they are 

 made up of two components.' 



1 Carnelkv, in 18S5 (Rril. Assoc. Reports), brought forward the !<tea 

 "that the elements are not elements in the strict sense of the frm, hut 

 are, in fsrl, comround radicals made UD of at least two -simple elements, 

 A .-ind B." The element A was supposed to be identical with carbon, while 

 'o P was assicned a negative weieht, - 2, and it was sueRested that it might 

 he the eiher of space. C. S. Palmer (Pror. Color.ido Scient. Soc.) assumed 

 the existence of two sub-elements, to which he gave the names "kalidium " 

 and " oxidium," and his views appear to have a eeneral resemblance to the 

 hvpothesis suegested in the text. The orijiinal artirle is abstracted in 

 Venables's " Periodic Law," and is referred to in f. otnot-s in Palmer's 

 translation of Nernst's " Theoretical Chemistry." 



