20 
MANUFACTURE  OP  PERCHLORIC  ACID. 
iron  tube  passing  through  the  materials  in  the  retort,  as  also 
the  retort,  had  fused.  The  iron  had  evidently  melted  below  its 
usual  fusing  point,  owing  to  the  fluorspar  acting  as  a  flux. 
Another  experiment  was  made  with  an  earthen  retort  of  half 
a  gallon  capacity.  A  porcelain  tube  was  passed  through  the 
tubulure  of  the  retort  to  within  an  inch  of  the  bottom.  Fluor- 
spar and  silica,  broken  into  fragments  of  the  size  of  large  peas, 
were  introduced  into  the  retort,  which  was  placed  in  a  wind 
furnace,  and  a  suitable  condensing  apparatus  connected.  When 
the  retort  had  reached  a  full  red  heat,  steam  was  introduced, 
from  a  steam  boiler,  by  means  of  suitable  connection.  For  a 
short  time  the  process  promised  well,  then  ceased. 
An  examination  of  the  contents  of  the  cold  retort  showed 
that  the  hot  silica  had  been  disintegrated  by  the  steam  sufficiently 
to  pack  the  mass  too  tight  for  the  vapor  to  penetrate  it. 
With  this  experience,  I  resorted  to  the  process  I  had  before 
employed  for  perchloric  acid,  which,  although  it  claims  no  nov- 
elty, may  interest  some  readers  of  the  Journal  from  its  details. 
The  first  step,  to  obtain  perchlorate  of  potash,  is  as  follows  : 
Heat  in  a  porcelain  crucible  of  8  oz.  capacity,  over  a  gas  fur- 
nace, eight  ounces  of  chlorate  of  potash,  until  the  salt  is  in  com- 
plete fusion,  taking  care  that  but  little  or  no  oxygen  is  evolved. 
Then  cover  the  crucible,  and  continue  the  same  amount  of  heat 
till  the  fused  salt  thickens  and  crusts  entirely  over  on  top.  A 
portion  of  the  salt  removed  from  the  crucible  should  now  impart 
but  a  light  yellow  color  to  pure  undiluted  muriatic  acid.  The 
crucible  is  now  removed,  and  allowed  to  cool.  When  cold,  the 
fused  mass  detaches  itself  completely  from  the  crucible  by  turn- 
ing it  upside  down. 
Dissolve  the  mass  in  2|  pints  of  boiling  water.  The  per- 
chlorate of  potash  crystallizes  out  on  cooling,  and  should  be 
washed  with  water  to  separate  the  mother  water. 
The  loss  of  weight  by  heating  the  chlorate  of  potash  was 
about  two  ounces  in  each  pound.  Amount  of  perchlorate  of 
potash  obtained  from  a  pound  of  chlorate,  about  eight  ounces. 
Four  hours*  heating  was  required  for  eight  ounces  of  chlorate  of 
potash,  the  gas  flowing  through  a  six  foot  burner,  to  about 
three-fourths  of  its  capacity. 
Perchlorate  of  potash  is  the  most  insoluble  of  all  the  salts  of 
