262  What  the  Atmosphere  is  Made  of. 
means  of  their  different  vaporizing  points  that  was  now  Used  in 
the  discoveries.  Xenon  proved  to  be  the  heaviest  gas  then  known, 
sixty-six  times  the  weight  of  hydrogen. 
At  this  time,  in  1898,  the  business  of  liquefying  air  assumed 
relatively  great  magnitude,  and  the  investigators  in  London  were 
able  to  acquire  a  considerable  quantity — fifteen  litres — of  argon. 
This  was  treated  in  the  various  ways  that  had  been  evolved  in 
previous  experiments  and  from  it  was  produced  or  rather  separated 
a  light  gas  with  red  spectrum.  This  was  neon.  Still  more  recently 
through  the  ability  to  get  larger  quantities  of  argon,  it  has  been 
possible  to  gather  as  much  as  120  cubic  centimetres  of  neon.  This 
has  been  tested  in  all  the  ways  known  to  chemistry  of  today  to 
determine  whether  still  other  gases  are  in  combination  with  it,  but 
it  has  resisted  separation  so  that  the  discussion  in  this  direction 
seems  to  be  finished. 
Although  it  would  seem  as  if  here  would  be  the  end  of  the 
story  of  gases  in  the  atmosphere,  the  final  lecture  brought  out 
the  fact  that  still  another  remained,  which  in  due  sequence  of  in- 
vestigation and  discoveries,  was  found  and  its  characters  deter- 
mined. This  was  niton,  so-called  because  when  frozen  it  shines. 
The  story  was  one  that  took  up  the  investigations  in  the  matter 
of  radio-activity.  It  is  known  that  electricity  may  be  gathered  high 
in  the  air  and  its  source  was  always  a  mystery.  It  is  now  known 
that  it  is  formed  by  the  decomposition  of  the  gases.  The  radio- 
activity story  led  up  to  the  showing  that  there  is  a  radium  emana- 
tion which  has  certain  peculiarities  and  relationships  in  a  curious 
group  of  activities.  This  is  now  known  to  be  a  gas  and  a  con- 
stituent of  air.  Its  presence  was  suspected  at  last  through  a  gap 
in  the  chemical  tabulation  of  elements.  Hydrogen  was  suspected 
of  being  possibly  in  combination  with  something;  the  temperature 
of  the  combination  was  lowered;  there  was  a  process  of  solidifica- 
tion at  a  temperature  at  which  hydrogen  was  still  unfrozen,  the 
latter  was  pumped  out  and  the  residue  examined.  Thus  the  gas 
niton  was  found,  an  unstable  one,  it  would  seem,  for  the  members 
of  the  radium  group  of  substances  are  continually  parting  with 
atoms  or  electrons  and  becoming  other  members  of  the  group. 
Helium  and  electrons  are  alternates  in  this  loss,  which  is  a 
phenomenon  giving  rise  to  new  concepts  in  chemistry. 
(  Am.  Jour.  Pharm. 
1       June,  1913. 
