6o8       Recent  Literature  Relating  to  Pharmacy.    { ^ecSerltoT 
estimated  to  be  present  in  the  atmosphere  in  the  ratio  of  about 
i  part  of  gas  to  a  million  of  air.  The  density  of  the  gas  is  esti- 
mated to  be  about  4078  and  its  atomic  weight  81-56. 
In  the  subsequent  experiments  that  were  made  with  liquid  argon 
it  was  found  that  the  first  fraction,  from  the  boiling  argon,  had  a 
density  of  14  67  and  a  ratio  of  specific  heats  of  166;  the  spectrum 
showed,  beside  the  lines  of  argon,  a  number  of  new  lines  of  red, 
orange  and  yellow  of  marked  brilliancy.  After  some  further  separ- 
ation of  the  contained  argon  the  density  was  found  to  be  9  76.  This 
new  gas,  which  was  designated  as  "  neon,"  while  it  still  contained  a 
fraction  of  argon,  also  contained  helium,  which  would  tend  to 
decrease  the  density  of  the  mixture  somewhat. 
Later  experiments  appear  to  indicate  that  this  gas  has  a  density 
of  about  9  96  and  an  atomic  weight  of  about  19-92.  It  is  present  in 
the  atmosphere  to  the  extent  of  from  10  to  20  parts  in  a  million. 
The  less  volatile  portions  of  the  liquefied  argon  they  considered  to 
contain  at  least  two  additional  elements  besides  krypton  and  argon. 
To  one  of  these  they  gave  the  name  "  Xenon  "  (stranger),  and  while 
they  did  not  have  an  opportunity  to  study  it  in  a  perfectly  pure 
condition,  they  determined  its  density  as  being  from  40-5  to  41-1. 
Later  investigations  appear  to  indicate  that  xenon  has  a  density  of 
about  64  and  an  atomic  weight  of  128.  It  must  be  considered  as  an 
extremely  rare  element  occurring  in  the  atmosphere  in  the  propor- 
tion of  fa  of  1  part  to  a  million  of  air. 
The  fourth  component  of  the  less  volatile  portion  was  given  the 
name  "  metargon."  It  was  a  source  of  much  perplexity,  as  its 
spectrum  was  found  to  resemble  the  so-called  "swan  spectrum"  of 
carbon  monoxide.  Subsequent  study  showed  that  the  supposed 
new  element  was  indeed  carbon  monoxide  which  had  been  intro- 
duced by  accidental  impurities  in  the  chemicals  used. 
All  of  these  elements  are  gases  and  all  are  chemically  inert ;  it 
would  appear  self-evident,  therefore,  that  they  would  form  a  distinct 
class  of  their  own  ;  but  how  to-  fit  them  into  the  existing  periodic 
system  developed  a  problem  that  has  been  attacked  by  several 
eminent  European  scientists,  and  has  also  been  the  cause  of  con- 
siderable discussion  pro  and  con  as  to  the  elementary  character  of 
these  substances,  and  the  correctness  of  the  available  data  concern- 
ing them. 
Several  schemes  have  been  proposed  to  fit  them  into  the  periodic 
