2.  (Moxon.)  Cow's  horn  or  hoof  is  baked  or
thoroughly  dried  and  pulverised;  to  tliis  is
added  an  equal  quantity  of  bay  salt,  and  the
whole  Is  made  into  a  paste  with  stale  chamber-
lye,  or  white  wine  vinegar ;  the  iron  is  covered
with  this  mixture,  and  bedded  in  it,  in  loam,
or  inclosed  in  an  iron  box.  In  this  form  it  is
laid  on  the  hearth  of  the  forge  to  dry  and
harden,  then  it  is  put  into  the  fire,  and  blown
till  the  lump  has  a  blood-red  heat  (no  higher).
It  is  hardened  as  before.
3.  Coat  the  goods  with  a  paste  made  of  a
concentrated  solution  of  prussiate  of  potash
and  loam ;  then  expose  them  to  a  strong  red
heat,  and  when  it  has  fallen  to  a  dull  red,
plunge  the  whole  into  cold  water.
4.  The  goods,  previously  polished  and
finished,  are  heated  to  a  bright-rod,  and
rubbed  or  sprinkled  over  with  prussiate  of
]iotash.  As  soon  as  the  prusstiate  appears  to
be  decomposed  and  dissipated  the  articles  are
plunged  into  cold  water.
Oba.  The  process  of  case-hardening  has
been  well  conducted  when  the  surface  of  the
metal  proves  sufficiently  hard  to  resist  a  file.
The  last  two  plans  are  a  great  improvement
upon  the  common  method.  By  the  topical
application  of  pru>siate  of  potash  (ferrocyanide
of  potassium)  any  part  of  a  piece  of  iron  may
be  case-hardened  without  interfering  with  the
rest.
Case  -  hardening  Powders.  Syn.  Case-
nABDENiNO  COMPOSITIONS.  1.  Prussiate  of
potash,  dried  and  powdered.
2.  E>russiateofpotash,3parts; sal-ammoniac,

1  part ;  mix.
