ON  A  NEW  ALKALI-METAL. 
163 
its  yellow  ray,  first  appears  ;  after  that  the  well-defined  red  ray 
of  lithium;  next  is  seen  the  paler  rays  indicating  potassium; 
and,  after  these  rays  have  disappeared,  they  are  replaced  by 
those  of  calcium  and  strontium,  which  remain  visible  for  some 
time.  The  absence  of  one  or  other  of  these  sets  of  rays  shows 
the  absence  of  the  corresponding  metals. 
We  are,  then,  by  this  method  placed  in  possession  of  an  analy- 
tical process  of  the  most  extraordinary  delicacy.  The  researches 
of  our  authors  prove  that  this  sensibility  almost  approaches  the 
infinite,  the  eye  being  able,  by  its  means,  to  recognise  the  pre- 
sence of  the  part  of  a  milligramme  of  chloride  of  sodium. 
It  must  not,  therefore,  be  a  matter  of  surprise  to  find  sodium 
distributed  almost  everywhere,  especially  in  the  atmosphere,  in 
which  is  almost  always  a  sufiicient  quantity  to  show  the  sodium 
ray.  The  same  may  be  said  in  great  measure  of  lithium.  In  a 
room  of  a  capacity  of  about  60  cubic  metres  was  exploded  a 
mixture  of  sugar  of  milk  and  chlorate  of  potassa,  containing  9 
milligrammes  of  carbonate  of  lithia.  The  lamp,  being  placed  at 
some  distance  off,  became  quickly  colored,  so  that  the  red  ray 
could  be  distinctly  visible  in  the  spectrum.  The  authors  esti- 
mated that  this  sensibility  reached  the  nine  millionth  part  of 
the  amount  taken. 
After  this  it  must  not  be  a  matter  of  surprise  to  find  that 
lithium  is  one  of  the  widest  spread  elements.  The  water  of  the 
Atlantic  was  found  to  contain  it.  It  was  also  found  in  the 
ashes  of  plants  grown  on  a  granite  soil,  in  the  vine,  in  tobacco, 
and  also  in  milk  and  in  human  blood.  In  the  mother-liquors  of 
tartaric  acid  manufactories  the  lithia  is  found  to  be  so  concen- 
trated as  to  be  worth  commercial  extraction  ;  and  the  same  may 
be  said  of  certain  mother-liquors  of  saline  springs. 
With  so  delicate  a  reaction  as  the  one  just  described,  of  an 
almost  infinite  sensibility,  and  applicable  to  all  metals,  the  pre- 
sence of  elements,  existing  in  so  small  quantities  as  to  entirely 
escape  ordinary  analysis,  may  be  rendered  visible.  Many  ob- 
servations tended  to  this  point,  and  MM.  Bunsen  and  Kirchhofi 
now  announce  definitely  (^AnnaL  der  Physik  und  Chemie^  that 
they  have  discovered  a  new  alkali-metal,  the  fourth  member  of 
the  group  of  potassium,  sodium,  and  lithium.  At  present  they 
have  only  found  it  in  very  small  quantities  in  the  mineral  water 
