606       Recent  Literature  Relating  to  Pharmacy.    { ^ecimbe^i™' 
of  much  research  and  discussion.  Its  spectrum  for  instance  appears 
to  vary  with  the  nature  of  the  electrical  energy  that  is  used  to 
energize  the  gas,  and  is  admittedly  complex  and  varied.  This  com- 
plex nature  of  the  spectrum,  as  well  as  the  accompanying  variations, 
has  been  made  a  basis  for  arguments  against  the  elementary  char- 
acter of  Argon. 
The  density  of  Argon  has  been  carefully  determined  by  Ramsay, 
who,  as  the  result  of  numerous  experiments,  announced  19  96  as  the 
true  value  for  the  density  of  the  gas ;  this  would  correspond  to  a 
molecular  weight  of  39-92  (o  =  16). 
Hehum. — This  element  was  first  noticed  in  the  spectrum  of  the 
chromosphere  during  an  eclipse  in  1868,  by  Jannsen,  who  noted 
a  brilliant  yellow  line,  which  was  close  to  but  not  identical  with  the 
well-known  ZUine  of  sodium.  This  he  designated  as  the  Z?3-line, 
and  in  the  same  year  Lockyer  assigned  the  name  "  Helium  "  to  the 
hypothetical  element,  of  which  this  line  was  characteristic. 
While  this  line  has  been  repeatedly  observed  since  then,  by  pro- 
jecting the  image  of  the  edge  of  the  sun,  on  the  slit  of  a  spectro- 
scope of  wide  dispersion,  and  has  also  been  found  in  the  spectrum 
of  some  of  the  fixed  stars  and  nebulas,  it  had  never  been  demon- 
strated to  exist  among  terrestrial  elements. 
After  the  discovery  of  argon,  Mr.  Myers,  the  mineralogist  of  the 
British  Museum,  wrote  to  Professor  Ramsay,  calling  his  attention  to 
the  fact  that  cleveite  (a  uranate  of  lead,  thorium  and  uranium)  had 
been  shown  by  Hillebrand  to  contain  nitrogen.  Myers  offered  the 
suggestion  that  this  mineral  might  contain  argon  or  might  have 
some  constituent  capable  of  entering  into  reaction  with  argon. 
This  suggestion  was  later  adopted  by  Professor  Ramsay,  who 
demonstrated  that  the  resulting  gas,  after  removing  the  nitrogen, 
not  only  contained  argon,  when  subjected  to  spectrum  analysis,  but 
also  showed  a  new  series  of  lines  in  the  red,  green,  blue  and  violet 
and  notably  a  brilliant  yellow  line.  Ramsay  later  sent  the  gas  to 
Crookes  for  examination  and  he  in  turn  reported  that  the  bright 
yellow  lines  were  undoubtedly  due  to  helium.  Experiments  made 
gave  3-89  as  the  maximum  density  of  the  gas,  and  the  ratio  of  the 
specific  heats  was  found  to  approximate  r66. 
The  gas  is  then,  as  was  to  be  expected  from  its  existence  in  the 
chromosphere,  very  light,  and  it  appears  to  be  monatomic. 
Helium  has  been  found  in  a  number  of  minerals,  almost  all  of 
