586 
VALERIANATE  OP  IRON. 
with  concentrated  solutions.  Another  thing  is  of  great  importance, 
namely,  that  the  valerianate  of  soda  used  should  be  entirely  free 
from  carbonate  or  caustic  soda,  a  thing  of  rare  occurrence  with 
the  usual  commercial  article  apparently,  more  especially  the 
carbonate  ;  this  may  be  known  at  once  by  its  solution  efferves- 
cing with  an  acid.  If  the  valerianate  of  soda  is  contaminated 
in  this  way,  the  result  obtained  is  unsatisfactory,  owing  to  the 
admixture  of  hydrated  oxide  of  iron. 
Mr.  Hanbury,  in  writing  to  me  respecting  the  preparation  of 
the  salt,  says  ;  "  We  prepare  it  by  decomposing  a  strong  solution 
of  persulphate  of  iron  by  one  of  valerianate  of  soda.  Upon  mix- 
ing the  solutions  a  copious  precipitate  of  an  extractiform  sub- 
stance of  a  brick-red  color  is  formed,  with  which  is  mixed  a  con- 
siderable quantity  of  sulphate  of  soda  in  small  crystals.  The 
precipitate  is  easily  washed  by  kneading  it  in  distilled  water  until 
the  latter  almost  ceases  to  be  affected  by  a  solution  of  baryta. 
The  resulting  product  requires  no  drying  beyond  the  pouring  off, 
as  far  as  possible,  of  the  water  which  somewhat  gradually  exudes 
from  the  mass ;  it  remains  in  the  form  of  a  soft  extract,  which 
becomes  harder  after  some  months.  We  never  attempt  to  dry 
it. 
The  method  I  have  adopted  myself  in  preparing  the  specimen 
now  before  you  is,  to  take  any  convenient  quantity  of  valerianic 
acid  which  is  to  be  exactly  saturated  with  a  concentrated  solution 
of  carbonate  of  soda,  heating  the  mixture  in  a  water-bath  so  as 
to  dispel  all  the  carbonic  acid ;  the  fluid  is  then  suffered  to  cool 
and  into  it  is  poured,  as  long  as  any  precipitate  is  produced,  the 
liquor  ferri  persulphas  of  the  British  Pharmacopoeia, — about  the 
same  quantity  by  measure  is  required  of  the  iron  solution  as  has 
been  used  of  valerianic  acid  ;  after  some  little  mixing  with  a  glass 
rod  the  precipitate  settles  down  into  a  semi-fluid  extract,  which 
may  be  repeatedly  washed  with  distilled  water  by  a  sort  of  knead- 
ing process,  until  the  sulphate  of  soda  is  entirely  removed;  it  is 
then  spread  out  as  thinly  as  possible  upon  glass  or  porcelain 
plates,  and  suffered  to  dry  either  by  simple  exposure  to  the  air 
or  by  a  gentle  heat,  then  chipped  off  and  preserved  in  bottles. 
The  salt  so  obtained  is  not  in  the  slightest  degree  deliquescent. 
The  best  test  of  its  purity  is  its  complete  insolubility  in  water 
and  the  ease  with  which  it  dissolves  in  spirit  of  wine. 
