TRANSACTIONS OF SECTION B. 593 



Section B.— CHEMISTRY. 



Peesident op the Section. — Professor W. Eamsat, Ph.D., F.R.S. 



THVIiSDAY, AUGUST 19. 

 The President delivered the following Address : — 



An Undiscovered Gas. 



A SECTIONAL address to members of the British Association falls under one of 

 three heads. It may be historical, or actual, or prophetic ; it may refer to the 

 past, the present, or the future. In many cases, indeed in all, this classification 

 overlaps. Your former Presidents have given sometimes a historical introduction, 

 followed by an account of the actual state of some branch of our science, and, 

 though rarely, concluding with prophetic remarks. To those who have an aflFec- 

 tion for the past, the historical side appeals forcibly ; to the practical man, and to 

 the investigator engaged in research, the actual, perhaps, presents more charm ; 

 while to the general public, to whom novelty is often more of an attraction than 

 truth, the prophetic aspect excites most interest. In this address I must endeavour 

 to tickle all palates ; and perhaps I may be excused if I take this opportunity of 

 indulging in the dangerous luxury of prophecy, a luxury which the managers of 

 scientific journals do not often permit their readers to taste. 



The .subject of my remarks to-day is a new gas. I shall describe to you later 

 its curious properties ; but it would be unfair not to put you at once in possession of 

 the knowledge of its moat remarkable property — it has not yet been discovered. 

 As it is still unborn, it has not yet been named. The naming of a new element is 

 uo easy matter. For there are only twenty-six letters in our alphabet, and there 

 are already over seventy elements. To select a name expressible by a symbol 

 which has not already been claimed for one of the known elements is difficult, and 

 the difficulty is enhanced when it is at the same time required to select a name 

 which shall be descriptive of the properties (or want of properties) of the element. 



It is now my task to bring before you the evidence for the existence of this 

 undiscovered element. 



It was noticed by Dobereiner, as long ago as 1817, that certain elements could 

 be arranged in groups of three. The choice of the elements selected to form these 

 triads was made on account of their analogous properties, and on the sequence of 

 their atomic weights, which had at that time only recently been discovered. Thus 

 calcium, strontium, and barium formed such a group ; their oxides, lime, strontia, 

 and baryta are all easily slaked, combining with water to form soluble lime-water, 

 strontia-water, and baryta-water. Their sulphates are all sparingly soluble, and 

 resemblance had been noticed between their respective chlorides and between their 

 nitrates. Regularity was also displayed by their atomic weights. The numbers 

 then accepted were 20, 42"5 and 65 ; and the atomic weight of strontium, 42'5, is 



1897. Q Q 



