SYRUPUS  FERRI  IODIDT. 
99 
strainer  and  washed  with  distilled  water  until  free  from  impuri- 
ties, then  again  allowed  to  drain,  and  dried  on  bibulous  paper  ; 
the  yield  was  1  lb.  8  oz.  of  dry  crystals.    The  washing  can  be 
accomplished  most  effectua'ly,  and  with  the  use  of  the  least 
water,  by  allowing  the  crystals  to  collect  in  a  stratum  on  the 
bottom  of  the  strainer,  and  then  adding  just  enough  distilled 
^vater  to  cover  the  surface  ;  any  sulphate  of  magnesia  is  dis- 
solved, and  this  together  with  the  yellow  mother  water  is  dis- 
placed by  the  descending  clean  water,  and  the  salt  is  left  perfectly 
white.    By  this  process  sulphite  of  magnesia  can  be  obtained  as 
pure  and  white  as  by  double  decomposition,  with  economy  in 
the  most  valuable  items,  time  and  labor,  the  yellow  coloration 
all  disappearing  by  the  simple  process  of  washing,  and  the  loss 
in  washing  is  small,  as  the  salt  is  difficultly  soluble  in  cold  water. 
The  yellow  color  seems  to  be  caused  by  an  impurity  soluble  in 
sulphurous  acid  (believed  to  be  iron)  and  it  only  appears 
when  the  acid  is  in  excess,  and  is  therefore  a-  good  indication 
that  the  magnesia  is  all  converted  into  sulphite.    When  made 
from  Henry's  magnesia,  no  yellow  color  was  visible  during  any 
step  in  the  process.    It  is  almost  needless  to  say  that  it  was  not 
found  profitable  to  evaporate  and  recrystallize  the  mother  water. 
SYRUPUS  FERRI  IODIDI. 
By  Edward  R.  Squibb,  M.  J). 
The  difficulty  of  keeping  this  preparation  without  change  has 
again  been  discussed  of  late  in  the  London  Pharmaceutical 
Journal,  and  the  insufficiency  of  the  various  plans  resorted  to 
have  been  pretty  well  shown  in  these  discussions,  and  in  the 
communications  elicited  thereby. 
In  a  very  considerable  experience  with  the  last  officinal  pro- 
cess (U.  S.  P.)  the  writer  has  only  once  seen  the  syrup  become 
discolored.  In  this  instance  a  syrup  made  in  September  and 
put  up  in  pound  bottles,  was  found  to  be  all  somewhat  discolored, 
though  not  uniformly  so,  and  all  shading  off  from  the  surface 
downward,  in  January  following.  This  single  instance,  however, 
proves  that  even  under  ordinary  good  care  and  nearly  uniform 
management,  some  slight  accident  may  determine  a  liberation  of 
