176 
On  Platinum  Black. 
{  Am.  Jotjb.  Pharm. 
\    April  1, 1872. 
results  at  which  he  arrived.  He  found  that,  although  soluble  glass  is 
of  itself  a  good  preservative  from  fire,  it  fulfils  the  object  better  when 
it  is  mixed  with  another  incombustible  body  in  powder.  Clay,  whit- 
ing, calcined  bones,  powdered  glass,  etc.,  may  all  be  employed  for  the 
purpose,  though  it  is  difficult  to  decide  which  of  them  is  the  best. 
A  mixture  of  clay  and  whiting  appears  to  be  better  than  either  used 
separately.  Flint  glass,  and  the  crude  soluble  glass  as  it  comes  from 
the  furnace,  are  excellent  additions.  The  powdered  soluble  glass 
ought  to  be  exposed  to  the  air  until  it  has  attracted  some  moisture  ; 
after  which,  if  it  be  mixed  with  the  solution  and  applied  to  any  body 
whatever,  it  will  in  a  short  time  form  a  coating  as  hard  as  stone, 
which,  if  the  glass  be  of  good  quality,  is  unalterable  by  exposure,  and 
resists  fire  admirably.  When  soluble  glass  is  used  for  rendering  wood 
fireproof  or  indestructible,  it  is  always  well  to  apply,  in  the  first 
place,  a  coating  of  the  pure  glass.  The  pores  are  in  this  way  filled 
up ;  while,  if  we  use  a  thick  and  paintlike  mixture  of  the  solution 
with  some  powder,  the  liquid  does  not  penetrate  beneath  the  surface, 
and  much  of  the  effect  is  lost.  When  properly  prepared,  soluble 
glass,  after  being  dried  by  exposure  to  the  air,  suffers  a  change  which 
renders  it  incapable  of  being  washed  off.  The  alkali  not  being  com- 
pletely neutralized  in  this  form  of  glass,  it  is  difficult  to  apply  oil 
paint  to  woodwork  that  has  been  treated  with  it ;  but  this  objection 
might  be  remedied  by  treating  the  prepared  surface,  when  dry,  with 
a  weak  solution  of  acid. — Industrial  Monthly  for  March,  1872. 
A  NEW  AND  READY  METHOD  OF  FORMING  PLATINUM  BLACK. 
By  J.  Lawrence  Smith. 
All  those  who  have  employed  the  usual  methods  of  forming  Plati- 
num Black  know  that  it  is  attended  with  some  little  trouble ;  having 
considerable  experience  in  the  decomposing  of  the  platin-chlorides  of 
the  alkalies  by  hydrogen,  and  by  ordinary  street  "gas,  the  resultant 
products  have  been  frequently  examined,  and  I  find  that  an  excellent 
platinum  black  can  be  thus  prepared,  whether  equal  to  the  best 
formed  by  other  processes  I  am  not  prepared  to  say.  I  prefer  taking 
platin-chloride  of  potassium,  and  were  it  not  that  rubidium  and  cae- 
sium are  too  expensive,  these  would  be  even  better,  for  their  atomic 
weights  are  higher  than  that  of  the  potassium,  and  consequently  the 
particles  of  platinum  are  more  widely  separated.    After  the  platin- 
