Piffard^s  Galvano-plaMic  Silvering.
The  cleansed  surfaces  of  the  articles  to
be  silvered  are  first  washed  with  a  so-
lution of  nitrate  of  silver,  so  that  a  thin
film  is  formed.  When  dry,  the  article
is  exposed  to  a  current  of  sulphide  of
hydrogen.  The  coating  thus  produced
is  very  conductive,  and  a  deposit  of
silver  adheres  very  firmly  to  it  when
the  article  is  brought  into  the  electro-
plating bath.
Silvering  Tiiicture.  Experiments
have  shown  the  following  receipt  for  a
silvering  tincture  to  be  excellent.  Pre-
pare the  following  solutions :

A.  2  parts  of  burned  lime,  5  of  grape
sugar,  2  of  tartaric  acid,  650  of  water.
The  solution  is  filtered  and  put  in
bottles  which  should  be  filled  entirely
full  and  well  corked.
B.  Dissolve  20  parts  of  nitrate  of
silver  in  20  of  aqua-ammonia,  and  then
add  650  of  water.
Just  before  the  tincture  is  to  be  used
mix  solutions  A  and  B  together,  shake
well  and  filter.  Metals  and  dry  vege-
table substances,  such  as  wood  tissues,
horn-buttons,  ivorj,  etc.,  can  be  sil-
vered with  this  fluid.
Cold  Silvering  of  Copper.  The  amal-
gam consists  of  1  part  of  the  finest  tin
filings  and  2  of  mercury,  which  are  in-
timately rubbed  together  in  a  porcelain
mortar.  When  a  semi-liquid  amaJsam
has  been  obtained,  add  1  part  of  silver
precipitated  from  a  nitnc  acid  solu-
tion by  metallic  zinc  and  thoroughly
washed.  When  tne  mixture  has  been
made  homogeneous  by  rubbing,  mix  it
thoroughly  with  about  8  parts  ot  bone-
dust.  The  process  of  silvering  is  car-
ried on  by  means  of  a  m  oist  clom.  The
silvering  is  accomplished  at  once^  and
is  both  beautiful  and  durable.  The
article  should  finally  be  rubbed  with  a


ELECTRO-PLATING,  QALVANOPLASTY,  ETC.
