306 
ON  AMMONIO-FERRIC  ALUM. 
nausea  or  headache.  It  generally  produces  a  slight  tendency  to 
constipation,  which  may  be  obviated  by  an  occasional  aperient. 
From  its  astringent  action  on  the  bowels,  it  has  been  found  useful 
in  choleraic  diarrhoea,  dysentery,  and  other  disorders  in  which 
tone  and  astringency  are  required." 
Since  I  prepared  this  salt  at  the  request  of  Dr.  Darrach,  it 
has  been  prescribed  by  him,  and  likewise  by  his  father,  Dr.  Wm. 
Darrach,  in  a  number  of  cases  ;  and,  as  both  these  physicians 
have  informed  me,  with  a  very  satisfactory  result,  considering 
the  short  experience  they  have  yet  had  with  it.  It  seems,  there- 
fore, not  improbable,  that  some  demand  for  it  may  ensue,  render- 
ing it  needful  for  pharmaceutists  to  supply  themselves  with  the 
identical  salt  mentioned  by  Dr.  Smith  as  answering  the  indications 
better  than  the  others  bearing  the  common  name  of  "  iron  alum." 
It  is  well  known  that  sulphuric  acid  forms  several  combina- 
tions isomorphous  with  common  alum,  yet  containing  no  alumina. 
Thus,  a  «  chromic  alum  "  may  be  formed,  in  which  the  sulphate 
of  sesquioxide  of  chromium  replaces  the  analogous  salt  of  alumi- 
num— a  "  manganic  alum,"  in  which  the  sulphate  of  manganese 
replaces  the  salt  of  alumina — and  a  "ferric  alum,"  in  which  the 
same  replacement  is  assumed  by  the  sulphate  of  the  sesquioxide 
of  iron.  These  salts  may  also,  in  like  manner  with  common 
alum,  be  varied  by  the  substitution  of  soda  or  ammonia  for  the 
potash  of  the  latter  salt.  It  is  this  last  combination  which  is  so 
particularly  recommended  by  Dr.  W.  Tyler  Smith,  the  chemical 
constitution  of  which  is  thus  represented  : — 
(NH3,  HO)  S03+Fe203  3S03+24HO. 
This  salt  is  readily  prepared,  if  certain  precautions  are  ob- 
served ;  but  as  my  own  first  and  second  attempts  to  produce  it 
failed  of  entire  success,  I  have  thought  that  a  record  in  the  pages 
of  the  Journal,  of  the  process  by  which  I  obtained  a  very  satis- 
factory article,  might  be  useful  to  other  pharmaceutical  chemists. 
The  formula  for  preparing  the  "  Ammonio-Ferric  Alum  " 
may  be  thus  stated : — 
Pure  crystallized  protosulphate  of  iron,       Iviij  (troy,) 
Sulphuric  acid,  f.5vij. 
Nitric  acid,  (common  strength,  or  36?  B.)  fjiiss.  (vel  q.  s.) 
Sulphate  of  ammonia,  gij  gij.  (troy.) 
Boil  the  sulphate  of  iron  in  two  pints  of  water,  and  add  to  it  the 
sulphuric  acid;  when  dissolved,  add,  in  small  portions  gradually, 
