PREPARATION  OF  PURE  SULPHATES. 
67 
and  tartaric  acids,  but  will  merely  observe  that  they  do  not  ap- 
pear to  enter  into  chemical  combination  with  the  iodide,  as  their 
effect  is  not  dependent  upon  any  definite  proportions. 
Having  stated  the  results  of  my  own  experiments,  I  must 
leave  it  to  the  judgment  and  experience  of  others  to  decide 
whether  these  preparations  are  worthy  of  a  place  in  the  catalogue 
of  remedial  agents.  They  will  require  the  test  of  longer  and 
more  extensive  employment  to  establish  their  claim,  but  I  feel 
assured  they  will  be  found  to  possess  some  valuable  character- 
istics that  will  recommend  them  to  both  the  Pharmaceutical  and 
Medical  professions. — London  Pharm.  Journ.  Nov.  1858. 
ON   THE    PREPARATION  OF  SOME  PURE  SULPHATES,  AND 
PARTICULARLY  SULPHATE  OF  COPPER. 
Br  Henry  Wurtz,  Prof.  Chem.  Med.  Coll.,  Washington. 
Commercial  blue  vitriol  always  contains  sulphate  of  protoxyd 
of  iron,  which  cannot  be  separated  by  crystallization,  owing  to 
the  fact,  determined  by  Mitscherlich,  that  ferrous  sulphate, 
when  crystallizing  with  sulphate  of  copper,  assumes  the  pente- 
hydrated  composition  and  triclinic  form  of  the  latter,  and  forms 
with  it  homogeneous  crystals.  It  has  appeared  to  me  desirable, 
therefore,  that  some  special  method  be  devised  for  the  separation 
of  the  iron,  both  in  order  that  the  chemist  may  possess  a  source 
of  pure  compounds  of  copper,  and  because  the  prescence  of  iron 
must  be  injurious  in  those  processes  of  dyeing,  calico-printing, 
etc.,  in  which  blue  vitriol  is  used,  and  in  the  preparation  of  the 
cupriferous  pigments,  verdigris,  Paris  green,  etc. 
In  undertaking  this,  my  aim  has  been  to  produce  a  method  by 
which  the  iron  may  be  directly  separated  or  abstracted  from  the 
solution  without  the  permanent  introduction  of  any  foreign  sub- 
stance. My  process  consists  essentially  of  two  steps  ;  the  first  of 
which  is  the  conversion  of  the  ferrous  into  ferric  sulphate,  by 
boiling  with  a  little  deutoxyd  of  lead ;  and  the  second  is  the  com- 
plete precipitation  of  the  ferric  sulphate,  by  boiling  with  a  little 
carbonate  of  baryta.  The  hot  solution  is  then  filtered  and 
allowed  to  crystallize,  when  large  crystals  of  beautiful  form  and 
