"^Apinjs™  }       On  Liq.  Ferri  Tersidphatis,  etc,  169 
The  author  thinks  that  glycerine  offers  advantages  in  the  investiga- 
tion of  this  subject  not  presented  by  any  other  medium,  as  the  ex- 
tracts remain  unchanged  for  a  long  time,  while  the  tissues,  being  little 
altered  after  exhaustion  of  their  ferment  by  repeated  treatment  with 
glycerine,  may  be  examined  under  conditions  hitherto  impossible.  He 
claims  that  these  results  are  also  of  practical  value  in  the  preparation 
'  of  the  so-called  pepsin  for  medical  purposes  ;  as  by  glycerine  a  pure 
palatable  peptic  liquid,  apparently  keeping  any  length  of  time  and 
certain  in  its  action,  can  easily  be  obtained. — Pharm.  Journ.^  Lond.y 
Jan.  7,  1871. 
FKOCESS  FOR  PREPARING  LIQ.  FERRI  TERSULPHATIS  AND 
LIQ.  FERRI  SUBSULPHATIS,  U.  S.  P.,  WITHO CJT  THE  FORMA- 
TION  OF  NOXIOUS  GASES. 
By  J.  Creuse,  of  Brooklyn,  N.  Y. 
The  best  method  for  preparing  the  persulphates  of  iron  perfectly 
pure  is,  undoubtedly,  to  run  a  stream  of  chlorine  gas  through  a  solu- 
tion of  the  protosulphate  previously  acidulated  with  the  proper  quan- 
tity of  sulphuric  acid.  But  this  is  obviously  impracticable  to  most 
pharmaceutists.  The  Pharmacopoeia  of  the  United  States  prescribes 
to  oxidize  the  protosulphate  of  iron  by  means  of  nitric  acid,  a  certain 
proportion  of  sulphuric  acid  being  added.  This  is  more  practicable, 
and  yields  a  good  product,  but  is  liable  still  to  several  objections. 
Expensive  vessels  are  required  for  boiling  a  mixture  of  sulphuric  and 
nitric  acids ;  a  good  draught  is  also  necessary  for  the  escape  of  the 
nitrous  fumes,  and  very  often  during  the  operation  the  vessels  are 
broken,  or  the  operator  is  annoyed  by  the  poisonous  gases  escaping 
into  the  room.  For  these  reasons,  many  pharmaceutists  prefer  to 
buy  the  articles  ready  made  ;  they  have  to  pay  a  high  price  for  it, 
and  to  depend  on  the  manufacturer  for  its  strength  and  purity. 
I  propose  this  new  method,  by  which  any  pharmaceutist  may  pre- 
pare his  own  Liq.  Ferri  Tersulphatis  or  his  Liq.  Ferri  Subsulphatis 
on  his  very  prescription-desk,  if  need  be,  and  with  the  usual  imple- 
ments found  in  all  drug-stores. 
R    Sulphate  iron  in  coarse  powder,  twelve  troyounces. 
Sulphuric  acid,  two  troyounces  and  sixty  grains. 
Chlorate  of  potassa,  three  hundred  and  forty-eight  grains. 
Boiling  water,  twelve  fluidounces. 
Dissolve  the  sulphate  of  iron,  in  the  boiling  water,  in  a  glass  mat- 
