"^Nov.TSr^  }  Preparation  of  Hydrosulphuric  Acid.  513 
DETERMINATION  OF  CITRIC  ACID. 
By  H.  KaMMERER. 
Soluble  citrates  mixed  v/ith  acetate  of  baryta,  either  hot  or  cold, 
produce  a  white  amorphous  precipitate,  being  3  BaO,  2  Ci2H50^,  3 
HO+14  aq. 
If,  after  precipitation,  an  excess  of  acetate  of  baryta  be  added, 
and  the  mixture  heated  in  a  water-bath,  the  precipitate  becomes  heavy 
and  granular,  it  loses  one-half  of  its  water  of  crystallization,  and  has 
now  the  composition  2  BaO,  2  G^^^fi^^,  3  HO+7  aq. 
The  presence  of  other  organic  acids  does  not  interfere  ;  the  granu- 
lar salt  is  absolutely  insoluble  in  water,  and  citric  acid  may  thus  be 
easily  determined.  If  the  solutions  are  very  dilute  they  must  be  con- 
centrated by  evaporation,  after  additions  of  acetate  of  baryta,  or  the 
precipitate  will  consist  of  crystalline  needles  containing  only  5  aq. — 
Fharm.  Journ.  and  Trans.  Oct.  7,  1871,  from  Zeitschr.  fur  Analyt. 
Chemie,  viii.  p.  298. 
PREPARATION  OF  HYDROSULPHURIC  ACID. 
By  J OHN  Galletly. 
In  making  some  experiments  on  the  action  of  sulphur  on  paraffin, 
I  have  found  that  a  mixture  of  these  substances,  either  in  equal  parts 
or  with  a  larger  proportion  of  sulphur,  when  heated  in  a  flask  not 
greatly  above  the  melting-point  of  the  sulphur,  begins  to  evolve  hy- 
drosulphuric acid,  and  continues  to  give  olf  this  gas  steadily,  while 
kept  moderately  heated,  for  a  considerable  time. 
I  have  used  this  process  repeatedly,  and  consider  it  the  most  con- 
venient for  laboratory  use.  With  a  round  flask  holding  about  a 
pound  of  the  materials  fitted  with  a  tube  bent  at  right  angles  about 
J-inch  bore  and  12  to  18  inches  long,  containing  a  little  loose  cotton 
wool,  and  having  a  smaller  tube  fitted  to  the  end  of  this  for  dipping 
into  the  liquid  through  which  it  is  desired  to  pass  the  gas,  a  conveni- 
ent stream  can  be  obtained  lasting  several  days.  The  production  of 
the  gas  can  be  stopped  and  renewed  at  pleasure  by  withdrawing  or 
applying  the  heat.  An  Argand  lamp  should  be  employed,  or  if  a  Bun- 
sen  is  used,  the  top  piece  should  be  on  the  tube  for  spreading  the 
flame,  so  as  to  avoid  heating  the  flask  on  one  spot.  Heavy  paraffin 
oil  used  for  lubricating  machinery  can  be  substituted  for  the  solid 
paraffin,  and  good  results  are  also  obtained  with  commercial  stearic 
acid,  but  with  the  latter  the  tube  conveying  the  gas  soon  becomes 
33 
