574 
Romance  of  Chemical  Elements.    {Am.-  J°uf-  PhaQrm- 
'  1     August,  1 918. 
stone  and  chalk  (compare  calcareous  and  the  German  kalk,  Swedish 
kalck,  even  the  French  chaux). 
Magnesium  sulphate  was  known  as  epsom  salt  to  N.  Grew  in 
1695,  who  prepared  it,  and  magnesium  alba  was  made  in  1707  by 
M.  N.  Valentin,  while  in  1755  J.  Black  showed  that  magnesium 
alba  and  lime  were  different  substances.  The  name  was  derived 
from  magnesite,  a  mineral  found  near  the  ancient  town  of  Magnesia 
(modern  Manisa)  in  Asia  Minor. 
Between  1800  and  1850  not  less  than  twenty-three  elements  were 
discovered  or  isolated,  mainly  by  the  experimental  work  of  Davy, 
Gay-Lussac,  Berzelius,  Wohler  and  others.  It  was  during  this  time 
that  the  methods  of  chemistry  were  worked  out  and  the  foundation 
of  the  science  established.  From  Table  VIII  the  results  of  their 
work  can  be  seen. 
The  Spectroscope. 
The  new  science  was  aided  in  i860  by  the  application  of  spectro- 
scopic methods  to  analysis,  and  as  a  result  several  new  elements 
were  discovered  by  this  method.  The  first  one  was  caesium,  whose 
presence  was  detected  by  the  "  fathers "  of  spectroscopy,  Robert 
Bunsen  and  Kirchhoff,  rubidium  followed  right  after,  then  thallium 
by  Crookes,  indium  by  Richter,  gallium  by  Lecoq  de  Boisbaudran. 
The  names  were  mostly  derived  from  the  Greek  words  for  the  color 
of  characteristic  lines  in  the  spectrum  (see  Tablle  III). 
The  spectroscope  was  then  employed  as  an  aid  in  the  separation 
of  the  rare  earths,  and  many  "new"  elements  were  found,  which 
proved  later  not  to  be  so.  But  some  were  really  new,  and  are 
embodied  in  our  present  list  of  elements  (see  Tables  IV  and  V). 
Periodic  System. 
The  rapid  discovery  of  a  great  many  new  elements  stimulated 
not  only  the  study  of  chemistry  and  made  it  more  popular,  but  it 
also  enabled  the  chemist  to  systemize  and  compare  his  results.  In 
every  science  we  can  follow  the  gradual  development  from  collect- 
ing facts  to  systematization.  So  we  find  the  first  attempts  of  a 
classification  in  1829  as  Doebereiner  published  his  "triads,"  that  is, 
he  put  always  three  elements  into  a  group,  in  which  there  was  a 
certain  relation  of  their  properties  (e.  g.,  Li-Na-K;  Ca-Sr-Ba; 
S-Se-Te;  etc.).  This  idea  was  further  developed  in  1854  by 
Crookes,  and  in  1865  by  DeChancourtois.    In  the  same  year  the 
