INFINITESIMAL QUANTITIES RAMSAY. 223 



capillary tube. Naturally, wo used a microscope to observe it. 

 However, it was easy to observe its properties. The emanation is 

 colorless like water when seen b}'" transmitted light. Seen by re- 

 flected light, it makes the tube phosphorescent, and its color depends 

 ii]ion the nature of the glass. In silica it emits a white light, in soda- 

 glass a lilac color, in potash-glass the color is greenish blue, Wlien 

 the emanation is liquefied in soda-glass its appearance recalls that 

 of a cA^anogen flame, being at the same time bluish and ])ink. 



This gas when cooled to —71° becomes opaque and solidifies. A 

 striking chauge of color is noticeable; the solidified emanation causes 

 the glass to emit a brilliant steel-blue glow like a small electric arc. 

 At a stUl lower temperature the color changes to yellow, aiid in liquid 

 air it becomes orange red. Wlien the tem])erature rises, the changes 

 of color- come in inverse order. Though its brilliancy is ver}'^ intense, 

 I scarcely think that its use can rival modern methods of illumma- 

 tion. 



We have succeeded in measuring the volume of this rare liquid, 

 and knowing, as we shall see later, that the density of the gas is 

 112.5, we may calculate the densit}^ of the liquid. It is very heavy, 

 5.7 times heavier than water. 



I have hitherto designated this gas by the name given it by Messrs. 

 Rutherford and Soddy. But it. doubtless belongs to the series of 

 inactive gases, and there are already three emanations — that of 

 radium, of thorium, and of actinium. The expression "radium 

 emanation" is not a very hapj)y o^ie, and wo had to seek a name to 

 indicate *)ne of the striking properties of the gas and at the same time 

 to recall its congeners of the argon series. We coined the name of 

 niton, signifying "shining." It is true we paid no heed to the 

 scruples of the purists, who forbid the addition of a Greek endmg to 

 a word of Latin origin. My excuse is that it was a generally accepted 

 custom among the Greeks to adopt Latin words (e. g., ooudapcov, dr^vd- 

 pcoVjTcpazxiijpcov, Kfjvooc, and numerous others). 



Dr. Collie and I succeeded in 1904 m measuring the wave lengths 

 of some of the spectral lines of niton. In collaboration with Mr. 

 Cameron other attempts were made. !Mr. Watson made in my 

 laboratory a thorough study of this question with nitoji purified by 

 me. According to Prof. Kicks, this spectrum presents close analogies 

 wdth the spectra of the inactive gases. Being itself an inactive gas, 

 there were many probabilities for its belonging in that series of ele- 

 ments. 



Several attempts have been made to determine precisely the atomic 

 weight of niton. I shall confine myself to mentioning the experi- 

 ments by means of diffusion of Curie and Danne, of Bums toad and 

 Wheeler, of Rutherford and Miss Brooks, of Makower, of Chaumont, 



