Am.  jour,  pharm.  \     Hydrofluoric  Acid  in  Glass  Industry.  2? 
January,  19 18.    >  J        1  J 
should  be  exercised  in  having  the  acid,  which,  if  at  times  cloudy, 
can  be  allowed  to  settle  and  poured  off  clear — thus  avoiding  addi- 
tional labor,  and  possibly  an  additional  dip  or  two. 
Lime  Glass. — A  mixture  of  three  parts  of  oil  of  vitriol  and  one 
part  hydrofluoric  acid  60  per  cent.  Begin  operation  with  four  suc- 
cessive short  dips  of  from  2,  3,  4  and  5  seconds  each.  Lime  glass 
differs  from  lead  glass  in  being  less  uniform,  which  means  that  better 
results  are  obtainable  when  atmosphere  is  clear  and  dry.  Cloudy 
and  inclement  weather  sometimes  blurs  the  glass,  due  to  the  acid's 
affinity  for  moisture.  This  can  be  obviated,  however,  by  adding 
hydrofluoric  acid  in  gradually  increased  quantities. 
Bloedite  Glass. — A  mixture  of  equal  parts  hydrofluoric  acid  60 
per  cent,  and  oil  of  vitriol.  Begin  by  giving  the  glass  a  first  dip  of 
only  one  second.  The  reason  for  this  is  to  clear  the  surface  so  as 
to  better  enable  you  to  make  a  finished  job.  Unless  this  is  done  the 
acid  clings  to  the  glass  and  becomes  smoky  and  sticky.  Then  pro- 
ceed with  successive  dips  of  3,  5  and  8  seconds  each,  and,  if  not  quite 
clear,  another  short  dip  of  3  seconds.  The  glass  should  be  well 
drained  before  each  dip. 
Lead  and  Manganese  Glass  without  Potash. — For  this  use 
a  mixture  7  parts  hydrofluoric  acid  and  2  parts  oil  vitriol.  First  dip 
20  seconds  ;  then  three  successive  dips  of  10  seconds  each. 
Spent  Hydrofluoric  Acid. — Best  incorporated  with  new  hydro- 
fluoric acid  as  follows,  and  corresponding  with  the  above  dip  by 
mixing : 
6  parts  spent  hydrofluoric, 
6  parts  hydrofluoric  60  per  cent., 
1  part  oil  vitriol. 
Fumed  Glass. — Due  to  improper  mixture  of  dipping  acid.  This 
difficulty  overcome  by  using  pumice  brush  and  pumice  buff  after- 
wards on  the  plain  metal,  and  thereafter  re-dip. 
Formula  for  Stamping. — 2  parts  hydrofluoric  acid,  by  weight, 
to  1  part  carbonate  ammonia,  by  weight,  using  sufficient  sulphate 
barytes  to  thicken  so  as  to  make  a  paste.  This  paste  can  be  spread 
on  a  pad  and  applied  with  a  rubber  stamp.  Either  48  per  cent,  or 
52  per  cent,  hydrofluoric  acid  should  be  used — 48  per  cent,  for  lead 
glass  and  52  per  cent,  for  lime  glass.  This  stamping  acid  should  be 
made  up  in  small  quantities  only  as  it  will  not  keep  any  length  of 
time. 
