48 
EXTRACTION  OF  THALLIUM. 
heat,  evolving  brown  vapors  into  the  air  at  a  temperature  little 
above  its  melting  point.  When  a  minute  fragment  of  thallium, 
or  of  any  of  its  salts,  is  introduced  into  the  flame  of  a  spirit 
lamp,  it  colors  it  of  a  most  intense  green,  which,  when  examined 
by  means  of  a  spectrum  apparatus,  appears  to  be  absolutely  mo- 
nochromatic, communicating  one  single  green  line  to  the  spec- 
trum. This  property  of  the  metal  is  now  too  well  known  to  re- 
quire further  remarks  ;  from  it  the  name  thallium  was  chosen. 
A  magnificent  green  fire  for  pyrotechnic  purposes  can  be  made 
with — ■  Chlorate  of  thallium  8  parts, 
Calomel  2  parts, 
Resin  1  part. 
The  chlorate  of  thallium  is  a  beautiful  crystalline,  difficultly 
soluble  salt,  which  may  be  prepared  by  dissolving  the  metal  in 
chloric  acid,  or  by  mixing  together  saturated  aqueous  solutions 
of  chlorate  of  potash  and  nitrate  of  thallium.    It  is  anhydrous. 
At  the  present  price  of  thallium,  its  employment  for  pyro- 
technic purposes  would  be  out  of  the  question  ;  but  a  very  little 
reduction  in  price  would  enable  its  magnificent  green  flame  to  be 
advantageously  employed  for  ship  signals,  as  the  extraordinary 
intensity  and  monochromatic  character  of  the  light  would  enable 
it  to  penetrate  a  hazy  atmosphere  without  the  change  of  color 
suffered  by  the  ordinary  green  lights  in  which  baryta  is  used.  The 
atomic  weight  of  thallium  is  203.  This  result,  however,  is  not 
deduced  from  sufficiently  accurate  analyses  to  render  it  entirely 
trustworthy,  and  I  am  now  engaged  in  determining  the  equiva- 
lent in  a  more  accurate  manner.  The  physiological  action  of 
thallium  is  a  matter  of  some  doubt.  I  cannot  say  that  it  has 
produced  any  particular  effects  upon  me,  although  I  have  been 
much  exposed  to  the  action  of  its  fumes  during  the  last  few 
months,  and  have  occasionally  swallowed  a  grain  or  two  of  its 
salts.  The  only  effect  which  I  have  noticed,  besides  the  staining 
of  the  hair  and  nails,  is  a  corrosive  action  which  the  sulphate  has 
on  the  skin,  burning  the  hands  and  rendering  the  epidermis  yel- 
low and  horny.    In  this  respect  it  acts  like  mercury  salts. 
Several  thallium  salts  are  sensitive  to  light.  The  protochlo- 
ride  and  double  phosphate  of  thallium  and  ammonia  are  especi- 
ally so. — Chem.  News,  London,  Oct.  3d,  1863. 
