150 
CADMIUM. 
are  brittle.  Its  combinations  are  not  distinguished  for  fluidity." 
Again,  The  combinations  of  platinum,  copper,  and  other  metals 
with  cadmium,  are  brittle  and  hard."  The  cause  of  this  he  as- 
cribes to  ^'  its  volatile  nature  and  want  of  affinity,"  which,  re- 
curring to  the  subject,  he  accounts  for  thus  : 
When  it  is  melted  with  any  other  metal  there  is  a  tendency 
on  its  part  to  evaporate  ;  the  slight  affinity  of  cadmium  for  other 
metals  causes  a  separation  of  its  atoms  from  those  of  the  other 
metal,  and  no  intimate  union  can  be  formed.  If,  therefore,  the 
alloy  cools  there  are  spaces  between  the  crystals  which  have 
been  occupied  by  the  expanded  atoms  of  cadmium,  and  in  cool- 
ing, these  are  filled  again  ;  this  causes  brittleness."  Treatise 
on  Metallurgy,  p.  465. 
All  this  is  strictly  true  of  some  of  its  combinations,  such  as 
the  particular  instances  which  he  cites,  although  by  no  means 
of  *<all,"  as  will  presently  be  seen. 
Other  authors,  although  less  explicit,  are  to  a  like  import,  as- 
cribing a  similar  general  character  to  the  metal,  with  examples 
in  illustration,  and  without  instancing  any  exceptions. 
In  a  copy  of  an  article  on  Alloys  of  Cadmium,  from  Berthiers 
Traits  des  Ussais,  tome  2,  p.  530,  furnished  me  by  the  patent 
office  as  authority  on  the  subject,  I  find  it  stated  in  general  terms 
that  "most  of  the  alloys  of  cadmium  are  brittle:"  the  individ- 
ual alloys  cited  are  particularly  characterized  as  brittle,  and  no 
mention  is  made  of  others — The  combination  with  mercury  is 
thus  described  :  Cadmium  unites  with  great  facility  with  mer- 
cury, even  when  cold.  The  amalgam  is  of  a  silver  white,  and 
texture  granular  and  crystalline.  It  can  be  obtained  in  octohe- 
drons.  It  is  hard  and  very  fragile.  Its  density  is  greater  than 
that  of  mercury.  It  fuses  at  75^  [centigrade.]  It  contains 
0.217  of  cadmium." 
Combined  in  these  proportions  the  compound  will  indeed  be 
comparatively  fragile ;  but  one  might  be  led  to  infer  from  this 
description  that  the  metals  combine  in  no  other  proportions.  I 
have  seen  this  particular  form  of  amalgam  cited  by  other  authors 
when  speaking  of  the  combination  of  cadmium  with  mercury,  but 
without  any  allusion  to  other  compounds  of  these  metals ;  al- 
though they  unite  with  facility  in  other  proportions,  forming 
amalgams  particularly  noteworthy  as  contrasted  with  those  of 
other  metals. 
