PKESIDENTIAL ADDRESS, 163 



chemical philosophy, and lo make it Uie mainspring and inspiration of the 

 greater part of modern inorganic research. 



The discovery ot argon, the announcement of which formed a notable feature 

 in the proceedings of the Association at the Oxford meeting in 1894, and the 

 recognition in. it of an element with an atomic weight of 40, raised doubts in 

 the minds of some as to the validity of the scheme of the elements based upon 

 the Periodic Law. It was indeed a time of testing the faith. The suggestion 

 that argon would prove to be a modified form of nitrogen was brushed aside 

 by the incontrovertible establishment of it as an element, endowed only with 

 specific physical properties and distinguished from all known elements by its 

 lack of any of those activities which characterise the remaining elements. But 

 argon was not destined to enjoy a splendid isolation for long. The researches 

 of Sir W. Ramsay soon brought helium to earth, and he and his colleagues 

 provided a number of companions for argon. So, in a very short period, was 

 recognised the existence of a group of gaseous elements forming a natural family, 

 whose molecules are monatomic, the members of which are distinguishable by 

 their spectra and atomic weights, but are all in agreement in their unreadiness 

 to take part in any chemical change. This inertness or nonvalence provided a 

 simple means of reconciliation with the periodic scheme of the elements, as all 

 that was required was simply to add to the eight groups of the table of elements 

 a zero group containing helium, neon, argon, krypton, and xenon, and with 

 niton, the emanation from radium, as a recent addition. If we are to accept 

 Mendeleeff's suggestion, the zero group should contain a member lighter than 

 hydrogen, in Series I., and in a zero series a still lighter representative of the 

 elements of the zero group, which he has postulated as the ' ether ' of the 

 physicist. 



Thus the discovery of argon has formed a starting point in the development 

 and a justification of the natural system of the elements, but it still remains, to 

 make the tabulation complete, that provision should be made for the accommoda- 

 tion of the rare earths. The paper published by Werner in 1905, under the 

 title ' A Contribution to the Development of the Periodic Sysoem,' shows how 

 this can be satisfactorily accomplished. 



The elements of the argon group form a valuable extension to the periodic 

 system, and the knowledge acquired in the investigation of these substances has 

 proved serviceable in the solution of problems in the realms of science and of 

 industry. The knowledge of the properties and behaviour of helium was 

 destined soon to play a part in the solution of the riddle of the radio-active 

 elements, whilst it is specially noteworthy that argon, the ' idle one,' should 

 have been pressed into industrial service. 



This fact suggests the thought that idleness has its uses, and at the present 

 time how satisfactory would it be were we able to find useful application for a 

 quality which appears to be plentifully and widely distributed in this countiy. 



The history of helium is still more astonishing, for not until thirty years 

 after its existence had been surmised from spectroscopic observations of the 

 sun was this element found to have a terrestrial existence, and now, as one of 

 the achievements of science during the war, we may look on its production in 

 bulk as a commercial proposition. Moreover, we are told ' that the advances 

 made in the production of helium warrant the opinion that, had the war con- 

 tinued after November 11, 1918, supplies of helium at the rate of 2,000,000 cubic 

 feet per month would have been produced within the Empire and the United 

 States, and helium-filled aircraft would have been in service.' ' 



Some of the speculations that the periodic system of the elements has given 

 rise to have been the subjects of communications to this Section. 



At the Aberdeen meeting Carnelley, whom I have already mentioned as an 

 ardent worker in this field, gave an account of a scheme based on the conception 

 that the elements are composite, having relations similar to those exhibited by 

 the paraffin hydrocarbons and the isologous series of radicals derived from them. 

 He regarded the elements, other than hydrogen, as made up of two simple 

 elements, A and B. A he identified with carbon, with the atomic weight of 12, 

 <ind B was assumed to have a negative atomic weight of 2. 



1 Nature, July 17, 1919. 



