76         Preparation  of  Biniodide  of  Mercury,  etc.  ' 
Feb.  1,  1874. 
Of  coarse  it  may  so  happen  that  ohe  British  Pharmacopoeia  does 
not  intend  that  the  acid  shall  be  saturated  with  oxide,  and  has  merely 
framed  its  formula  with  other  objects  in  view. 
If  it  were  so  contemplated  I  think  a  great  improvement  in  the  for- 
mula would  have  been  made  if  a  salt  had  been  recognized  that  would 
have  sealed  easily,  and  represented  the  best  specimens  as  met  with 
in  trade. 
An  examination  of  the  ammonio-citrate  of  the  leading  London 
manufacturers  indicates  that  at  the  present  time  uniformity  is  the 
exception  rather  than  the  rule  ;  that  the  British  Pharmacopoeia  scales 
are  not  to  be  met  with ;  that  the  preparation  of  the  London  Pharma- 
copoeia, or  a  modification  of  it,  is  still  used  ;  and  that  the  complete 
saturation  process  is  in  some  cases  followed. 
London  Pharmaeopceia,  1851, .       .        34*0  (determined). 
British  Pharmacopoeia,  1867,     .       .27*4  " 
Manufacturing  Process  (saturation)         30-7  w' 
Trade  specimens,       ...        (1)  26*0 
.    (2)  24-1 
(3)  30-1 
.    (4)  30-0 
(5)  33-4 
.    (6)  33-3 
(7)  29-4 
As  uniformity  in  all  substances  used  in  medicine  is  of  vital  import- 
ance I  would  suggest  that  at  the  earliest  convenient  date  the  use  of 
ferric  oxide  sufficient  to  the  complete  saturation  of  the  acid  by  the  ' 
aid  of  a  water-bath  heat  be  recognized,  and  that  the  formula  of  the 
British  Pharmacopoeia  be  amended  by  substituting  nine  and  a  half 
fluid  ounces  of  the  persulphate  of  iron  solution  for  the  present  quan- 
tity of  eight  fluid  ounces,  or  as  much  hydrated  ferric  oxide  to  one 
hundred  parts  of  citric  acid  as  shall  be  equivalent  to  fifty  parts  (49*6) 
of  anhydrous  ferric  oxide. 
Laboratory,  40,  Alder sg ate  street,  E.  C. 
— Pharm.  Journ.  and  Trans.,  Dec.  13,  1873. 
ON  VARIOUS  METHODS  FOR  THE  PREPARATION  OF  BIN- 
IODIDE  OF  MERCURY. 
By  E.  B.  Shuttleworth. 
In  devising  or  selecting  a  formula  for  the  preparation  of  any  com- 
pound there  are  three  considerations  which  are  essential  to  a  correct 
and  satisfactory  conclusion.    These  are,  that  the  contemplated  prod- 
