22^     CHEMICAL  ANALYSES  BY  SPECTRUM  OBSERVATIONS. 
racterized  by  some  one  or  more  special  lines,  it  is  easy  to  make 
a  qualitative  analysis  of  a  compound  containing  several  ele- 
ments :  thus,  KirchofF  and  Bunsen  were  enabled  to  exhibit  the 
reactions  of  'potassium,  sodiurrij  lithium,  calcium,  and  strontium, 
in  several  mineral  waters ;  to  show  the  bands  of  sodium,  'potas- 
sium, lithium,  and  calcium  in  the  ash  of  a  cigar  moistened  with 
hydrochloric  acid,  and  to  point  out  differences  in  the  composi- 
tion of  various  limestones.  But  the  greatest  triumph  of  the  new 
method  of  analysis  was  the  discovery  of  a  fourth  member  of  the 
group  of  alkali  metals.  While  working  on  the  residue  of  a 
mineral  water  from  Kreuznach,  a  spectrum  was  obtained  which 
gave  lines  as  simple  and  characteristic  as  those  of  lithium  and 
sodium,  but  which  were  blue,  and  were  not  referable  to  any  known 
element ;  these  indefatigable  chemists  evaporated  down  no  less  a 
quantity  than  tiventy  tons  of  the  water,  and  obtained  240  grains 
of  the  platinum  salt  of  the  new  metal,  which  they  call  ccesium, 
from  the  Latin  word  ccesius,  signifying  grayish  blue,  that  being 
the  tint  of  the  two  spectral  lines  which  it  shows.  The  new  metal 
is  very  analogous  to  potassium,  but  differs  from  it  in  the  solu- 
bility of  its  nitrate  in  alcohol.  Its  equivalent  number  is  117, 
being  exactly  three  times  that  of  potassium.  It  is  scarcely  pos- 
sible to  overrate  the  probable  importance  to  chemical  science  of 
this  new  and  beautiful  method  of  analysis.  "  In  spectrum 
analysis,"  observe  the  authors,  the  colored  bands  are  unaf- 
fected by  any  alteration  of  physical  conditions,  or  by  the  pre- 
sence of  other  bodies.  The  positions  which  the  lines  occupy  in 
the  spectrum,  indicate  the  existence  of  a  chemical  property  as 
unalterable  as  the  combining  weights  themselves,  and  may  there- 
fore be  estimated  with  almost  astronomical  precision  ;  it  ex- 
tends almost  to  infinity  the  limits  within  which  the  chemical 
characteristics  of  matter  have  hitherto  been  confined.  By  an 
application  of  the  method  to  geological  inquiries,  the  most  valua- 
ble results  may  be  expected  ;  it  opens  out,  moreover,  the  inves- 
tigation of  an  entirely  untrodden  field,  stretching  even  beyond 
the  solar  system,  for  in  order  to  examine  the  composition  of  a 
luminous  gas,  we  require,  according  to  this  method,  only  to  see 
it ;  and  it  is  evident  that  the  same  mode  of  analysis  must  be  ap- 
plicable to  the  atmosphere  of  the  sun  and  of  the  brighter  fixed 
stars." — Chemist  and  Druggist,  Feb.  16th,  1861. 
