^'"*ju'iy%9n'''"™'}  ^^/'^^  Determination  of  Sulphuric  Acid.  345 
I  therefore  describe  this  most  simple  and  rapid  determination 
of  sulphuric  acid,  taking  normal  sulphuric  acid  as  a  standard  with 
49.05  Gm.  of  H0SO4  to  the  litre :  10  ex.  of  n/^ — H2SO4  are  trans- 
formed from  a  burette  or  pipette  to  a  beaker  of  300  or  400  ex.,  the 
acid  is  then  diluted  with  three  or  four  times  or  more  by  volume  of 
distilled  water  and  boiled  for  a  few  minutes ;  to  this  solution  is 
added  a  few  c.c.  of  cone.  HQ  or  HNO3,  stirred,  and  while  boiling 
add  the  boiling  or  hot  solution  of  barium  chloride  or  nitrate  10  or 
15  c.c.  (10  per  cent,  solution)  ;  stir  and  mix,  and  keep  mixed  solu- 
tion boiling  for  a  further  few  minutes ;  then  transfer  to  a  warm 
place  or  water  bath  if  convenient  to  have  for  settling  of  the  macro- 
crystalline ppt.  While  the  ppt.  settles  in  water  bath  the  porous 
crucible  is  heated  and  weighed  which  can  be  done  very  easily.  I 
generally  weigh  the  crucible  under  the  same  condition  without  the 
use  of  an  exsiccator  and  was  able  to  obtain  very  satisfactory  results. 
The  weighed  crucible  is  then  attached  to  a  water  pump  of  any 
kind  with  the  so-called  carbon  filter  with  rubber  stopper,  and  a  mod- 
erate stream  of  water  will  filter  the  hot  barium  sulphate  ppt.  abso- 
lutely clear  through  the  porous  clay  crucible,  leaving  ppt.  nearly 
white,  and  after  washing  with  hot  water,  or  better,  slightly  acidu- 
lated water  to  free  the  ppt.  from  barium  chloride  or  nitrate  which 
can  be  tested  for  such  with  silver  nitrate  or  diphenylamin  solution, 
in  the  filtrate.  The  porous  crucible  with  ppt.  is  then  carefully  heated 
with  a  Bunsen  burner  and  after  moisture  has  been  driven  off  the 
crucible  can  then  be  strongly  heated  and  weighed  to  constancy. 
I  have  worked  out  a  table  based  on  the  principle  of  normal 
sulphuric  acid  49.05  Gm.  of  H^SO^  to  1000  c.c.  Aq.  Dest.  figuring 
the  acid  from  barium  sulphate  from  9  c.c.  tO'  11  c.c.  This  will 
enable  the  chemist  to  know  exactly  the  strength  of  acid  to  dilute 
or  to  make  stronger  if  necessary.  Ten  c.c.^  which  averages  to  about 
0.4905  Gm.  H0SO4,  is  about  or  approximately  the  sufficient  amount 
of  any  sulphate  to  be  analyzed,  with  exception  of  sulphate  ores  to 
more  conveniency  in  some  cases  to  i  Gm.  and  more. 
This  table  can  also  be  used  for  any  sulphur  analysis  considering 
that  the  BaS04  as  noted  in  the  table  corresponds  to  the  product 
analyzed. 
The  crucible  as  such  can  be  used  for  the  analysis  of  different  col- 
loidal and  semicolloidal  ppts.  with  the  same  accuracy  and  less  time.  I 
have  tried  the  crucible  for  different  analyses  and  found  it  to  be 
satisfactory. 
