152     THE  PREPARATION  OF  HYDROGEN  REDUCED  IRON. 
of  the  former ;  the  amalgam  is  nearly  equal  in  malleability,  but 
possesses  less  strength.  These  mixtures  are  remarkable  in  view 
of  the  fact  that  most  amalgams  are  exceedingly  frail  and  brittle. 
A  mixture  of  two  or  three  parts  of  tin  with  one  part  of  mercury 
is  so  fragile  as  almost  to  drop  to  pieces  in  handling :  the  amal- 
gams with  lead,  bismuth,  &c.,  are  similar. 
The  fusibility  of  the  compounds  of  cadmium  and  mercury  is 
nearly  that  of  the  mean  of  their  constituents,  as  indeed,  appears 
to  be  the  case  with  other  amalgams.  I  do  not  perceive  that  mer- 
cury acts  as  a  fluidifying  agent  in  alloys — it  does  not  strictly 
promote  fusibility  but  serves  merely  to  communicate  of  its  own 
fluidity  to  the  compounds  in  nearly  the  ratio  in  which  it  is  em- 
ployed ;  it  does  not,  like  cadmium,  bismuth,  &c.,  confer  any  new 
property  in  this  respect.  Being  fluid  at  39*^  below  the  zero  of 
Fahrenheit's  scale,  it  will  of  course,  if  it  only  retains  its  own  pro- 
perty, reduce  the  melting  point  of  the  compounds  into  which  it 
enters  as  an  ingredient,  below  that  of  the  metals  with  which  it 
is  united. 
Most  of  the  mixtures  of  mercury  with  other  metals,  although 
it  may  form  certain  definite  compounds  with  them,  indicate  com- 
bination by  simple  solution  and  mechanical  admixture  rather 
than  by  chemical  affinity.  With  cadmium,  however,  it  exhib- 
its a  marked  affinity  for  forming  amalgams,  or  as  they  might  be 
appropriately  designated,  alloys  which  possess  distinctive  char- 
acters, indicating  a  true  chemical  combination. 
But  I  leave  these  speculations  to  professed  chemists,  hoping 
the  points  herein  referred  to  may  serve  to  incite  attention  to  a 
subject  which  I  think  will  repay  investigation. — Journ.  Franklin 
Institute^  Aug.  1860. 
ON  THE  PREPARATION  OF  HYDROGEN  REDUCED  IRON,  AND 
ON  THE  MEANS  OF  PRESERVING  IT  FROM  OXIDATION. 
By  M.  S.  De  Luca. 
Pure  iron  in  a  state  of  minute  division,  known  by  the  name 
of  ''iron  reduced  by  hydrogen,"  so  much  used  in  medicine,  is 
now  largely  manufactured,  but  without  the  least  security  as  to 
