58 A. W. Steivart on 



formed an, exact i)arallel to thof^c of the inert gases of the atmos- 

 phere discovered l)y Sir \\'iniani Kamsay. Niton refuses to coni- 

 bine with any other element, even when heated to a red heat in 

 the itresoncc of reactive metals. It thus shows itself akin to 

 argon and its congeners of the Zero Group in the Periodic Table. 

 But while thus chemically inert, niton is very powerfully 

 radioactive. ^Yhen it is dissolved in water, it decomposes the 

 liquid into oxygen and hydrogen, just as the electrodes of a 

 battery do. It sends out a very intense stream of alpha-particles, 

 Avith all the jtroperties which such emitted particles ordinai'ily 

 display. It aflects a charged electroscope when brought near to 

 it ; and it causes a fluorescent screen to glow brightly when the 

 gas is blown across the surface. 



In order to handle niton, special precautions had to be taken. 

 In the course of the fundamental experiments of Sir William 

 Ramsay and Mr. Soddy, the largest volume of niton obtainable 

 was about 0-000,000,32 cubic inches ; and the manipulation of 

 this tiny bulk of gas was extremely difficult. In order to trans- 

 fer the niton from vessel to vessel, it was necessary to mix the 

 radioactive gas with a large bulk of air and then drive the mixture 

 from its reservoir to the place where it was required. In this 

 way the loss of a fraction of a cubic inch of the mixture only 

 represented the mislaying of an immeasurably small quantity of 

 niton. 



Sir William Eamsay, hoAvever, actually manipulated pure 

 niton, unmixed with air. Working merely with the almost in- 

 visible volume mentioned above, he and Dr. Whytlaw-Giay were 

 able to liquify and solidify niton, determine its critical temperature 

 and pressure, and study its behaviour under the microscope as it 

 passed from state to state. 



In order to fix definitely the place of niton in the Periodic 

 Table, it was necessary to determine its atomic weight ; and the 

 only way in which that could be done was by the determination 

 of the gaseous density of the element — i.e., by weighing a known 

 volume of the gas. The experimental difficulties in the way of 



