ON  THE  NEW  METAL  THALLIUM. 
405 
Sulphuric  and  nitric  acids  are  those  which  attack  thallium 
easiest,  especially  by  the  aid  of  heat.  Hydrochloric  acid  even 
boiling  dissolves  it  very  difficultly.  Under  these  circumstances, 
there  form  white  soluble  salts,  sulphate,  and  nitrate,  crystallis- 
ing readily,  and  a  slightly  soluble  chloride,  but  capable  also  of 
crystallising. 
The  chloride  formed  by  the  direct  action  of  chlorine  or  by 
aqua  regia  is  deposited  from  its  aqueous  solution  in  the  form  of 
magnificent  yellow  plates,  which  appear  to  belong  to  the  rhombo- 
hedral  system. 
Zinc  precipitates  thallium  from  its  sulphate  and  nitrate  solu- 
tions ;  the  new  metal  deposits  in  brilliant  crystalline  plates. 
Hydrochloric  acid  and  protochlorides  give,  with  the  same 
solutions,  a  white  precipitate  of  chloride  of  thallium  resembling 
chloride  of  silver,  but  slightly  soluble  in  water ;  otherwise,  very 
little  soluble  in  ammonia,  and  inalterable  by  light. 
Hydro-sulphuric  acid  has  no  action  on  pure  neutral  or  acid 
solutions  ;  but  if  they  are  alkaline,  a  voluminous  black  precipitate 
of  sulphide  of  thallium  is  produced,  which  readily  settles  to  the 
bottom  of  the  vessels,  and  is  insoluble  in  an  excess  of  precipi- 
tant. 
Finally,  potash  soda  and  ammonia,  do  not  displace  oxide  of 
thallium  in  combination  with  sulphuric  and  nitric  acids. 
Natural  State  and  Extraction  Thallium  cannot  be  consider- 
ed as  very  rare  in  nature.  It  exists,  indeed,  in  many  kinds  of 
pyrites,  which  are  used  at  the  present  time  in  large  quantities, 
principally  for  the  manufacture  of  sulphuric  acid.  I  may 
especially  mention  Belgian  pyrites,  from  Theux,  Namur,  and 
Phillippeville.  I  have  also  found  it  in  mineralogical  speci- 
mens from  Nantes,  and  Bolivia  in  America. 
Strictly  speaking,  thallium  might  be  prepared  from  these 
pyrites  ;  but  it  is  much  easier  to  prepare  it  by  using  the  depo- 
sits from  the  lead  chambers,  where  it  accumulates  in  relatively 
large  quantities  during  the  manufacture  of  sulphuric  acid.  It  is 
from  these  thalliferous  deposits  that  I  have  extracted,  by  a 
method  given  in  my  memoir,  the  chlorides  of  thallium  which 
formed  the  starting  point  of  the  study  which  I  have  made  of  the 
new  metal  and  its  compounds. 
As  to  the  metal  itself,  it  may  be  reduced  from  one  of  its  saline 
