404       REMARKS  ON  MONSEl/S  PERSULPHATE  OP  IRON. 
fluid  grammes,  by  the  addition  of  q.  s.  distilled  water  ;  allow  it 
to  cool  and  filter. 
"  The  clear  solution  marks  45°  of  Baume"s  pese*-sels.  It  has  a 
very  deep  red  brown  color,  is  inodorous,  and  is  extremely  astring- 
ent to  the  taste  without  causticity.  When  largely  diluted  with 
water  it  separates  after  many  hours  into  a  soluble  acid  sulphate 
and  an  insoluble  subsulphate.  It  concentrates  by  evaporation 
to  the  consistence  of  honey,  and  if  then  spread  on  plates  of  glass 
it  may  be  dried  at  a  temperature  above  95°  Fahr.,  and  obtained 
in  brilliant  red  scales  like  citrate  of  iron.  These  scales  retain 
25  per  cent  of  water,  dissolve  easily  in  a  small  quantity  of  water 
without  decomposition  and  reproduce  the  original  solution. 
When  evaporated  with  less  care  to  dryness,  a  greenish  yellow 
anhydrous  salt  is  obtained,  soluble  slowly  in  cold  water,  requiring 
48  hours  to  reproduce  the  original  solution,  and  immediately  in 
boiling  water  except  a  slight  yellow  residue. 
"  The  salt  in  scales  is  soluble  in  alcohol  without  decomposition. 
The  solution  at  45°  B.  is  susceptible  of  dissolving  hydrated 
sesquioxide  of  iron  by  digestion,  but  it  cannot  be  evaporated 
vnthout  decomposition.  When  sulphuric  acid  is  dropped  into 
the  solution  it  is  decolorized,  and  an  excess  of  acid  gives  a  solid 
compound,  white  as  plaster. 
"  Particular  attention  is  directed  to  the  manner  in  which  it 
comports  itself  with  the  albumen  of  eggs  and  with  blood  ;  some 
drops  produce  a  very  voluminous  and  very  consistent  clot,  ab- 
solutely insoluble,  which  continues  to  swell  and  harden  for  many 
hours.  The  new  sulphate  contains  2|  equivalents  of  sulphuric 
acid  to  one  equivalent  of  sesquioxide  of  iron,  and  it  is  certainly 
preferable  to  the  sulphate  of  the  peroxide  described  by  Sou- 
beiran,  which  is  very  caustic  and  contains  a  great  excess  of  nitric 
acid." 
M.  Soubeiran  remarks  in  his  note  at  page  210,  "I  have  re- 
peated the  experience  of  M.  Monsel  ;  it  is  perfectly  success- 
ful, and  his  process  will  be  accepted  always  for  procuring  a 
solution  of  the  ferric  sulphate.  The  salt  dried  in  a  stove  is  so 
deliquescent  as  not  to  bemanagable,  and  if  it  is  intended  to  pre- 
serve it  in  a  dry  state,  it  is  necessary  to  have  recourse  to  greater 
heat  which  renders  the  product  like  that  by  the  old  method." 
In  a  more  recent  paper,  (Jour,  de  Pharmacie  et  de  Chimie,) 
