156  Argon.  {Ami,S™' 
ARGON ;  A  NEW  CONSTITUENT  OF  THE  ATMOSPHERE. 
At  a  meeeting  of  the  Royal  Society,  held  January  31,  1895, 
Lord  Rayleigh  and  Professor  William  Ramsay  presented  a  paper 
which  contained  the  facts  necessary  to  the  establishment  of  a  new 
element. 
It  had  previously  been  shown  by  Lord  Rayleigh  that  nitrogen 
extracted  from  chemical  compounds  was  about  y2  per  cent,  lighter 
than  that  obtained  from  the  atmosphere.  He  was  led  to  study 
the  atmospheric  gases  under  a  number  of  different  conditions,  one 
of  which  consisted  in  submitting  a  mixture  of  air  and  oxygen  to  the 
prolonged  action  of  electric  sparks ;  another  involved  the  withdrawal 
of  nitrogen  from  air  by  means  of  red-hot  magnesium.  In  both  cases 
a  gas  was  obtained  whose  properties  could  not  be  reconciled  with 
those  of  any  known  element. 
To  prepare  argon  on  a  large  scale,  air  is  freed  from  oxygen  by 
means  of  red-hot  copper.  The  residue  is  then  passed  from  a  gas 
holder  through  a  combustion  tube,  heated  in  a  furnace,  and  contain- 
ing copper,  in  order  to  remove  all  traces  of  oxygen  ;  the  issuing  gas 
is  then  dried  by  passage  over  soda-lime  and  phosphorus  pentoxide. 
It  then  enters  a  combustion  tube  packed  tightly  with  magnesium 
turnings,  and  heated  to  redness  in  a  second  furnace. 
A  single  tube  of  magnesium  will  absorb  from  7  to  8  liters  of 
nitrogen.  The  temperature  must  be  nearly  that  of  fusion  of  the 
glass,  and  the  current  of  gas  must  be  carefully  regulated,  else  the 
heat  developed  by  the  union  of  the  magnesium  with  the  nitrogen 
will  fuse  the  tube. 
Having  collected  the  residue  from  100  to  150  litres  of  atmospheric 
nitrogen,  which  may  amount  to  4  or  5  litres,  it  is  transferred  to  a 
small  gas  holder  and,  by  means  of  a  species  of  self-acting  Sprengel's 
pump,  the  gas  is  caused  to  circulate  through  a  series  of  tubes  of 
copper,  copper  oxide,  soda  lime,  phosphorus  pentoxide  and  red-hot 
magnesium  turnings,  until  it  is  freed  from  any  possible  contamina- 
tion with  oxygen,  hydrogen,  hydrocarbons  or  nitrogen.  It  is  pre- 
served over  mercury,  or  over  water  saturated  with  argon. 
The  solubility  of  the  gas  prepared  by  means  of  red-hot  magne- 
sium was  found  to  be  4-05  per  100  at  13-9°;  it  is,  therefore,  two 
and  one-half  times  as  soluble  as  nitrogen  and  possesses  approxi- 
mately the  same  solubility  as  oxygen. 
