GRANULAR  EFFERVESCENT  CITRATE  OF  MAGNESIA.  65 
three  portions,  covered  lightly  with  paper  to  prevent  accession 
of  dust,  were  exposed  to  the  air  at  the  ordinary  temperature. 
Two  were  made  in  January,  and  one  in  June  last:  but  as  neither 
portion  has  yet  become  rancid,  I  cannot  definitely  answer  the 
second  clause  of  the  query. 
Three  portions  of  ointment  of  red  oxide  of  mercury  were  also 
made :  the  first  with  lard,  the  second  With  ointment  of  benzoin, 
and  the  third  with  benzoinated  lard.  The  three  portions  when 
made  were  of  the  same  pink  color  and  perfectly  smooth;  they 
were  made  on  the  20th  of  June,  and  were  exposed  in  the  same 
manner  as  the  mercurial  ointment  for  nearly  two  months  ;  at  the 
end  of  which  time  they  were  found  in  the  following  condition : 
The  first,  made  with  lard,  had  changed  in  color  to  dark  green, 
had  separated  into  a  granular  and  a  semi-fluid  substance,  and  had 
become  very  rancid.  The  second,  made  with  ointment  of  ben- 
zoin, had  not  changed  color  nor  become  rancid,  but  had  separated 
in  the  same  manner  as  the  first.  The  third,  made  with  benzoin- 
ated lard,  was  entirely  unchanged  in  odor  or  appearance,  and 
looked  precisely  as  if  just  made. 
Experiments  with  other  ointments  have  not  been  tried,  but 
there  is  no  doubt  that  the  benzoinated  lard  can  be  used  in  many 
of  the  ointments  of  the  Pharmacopoeia,  without  affecting  their 
medicinal  qualities. 
Boston,  August,  1866.       — Proc.  Am.  Pkarm.  Ass.  1866. 
ON  GRANULAR  EFFERVESCENT  CITRATE  OF  MAGNESIA. 
By  James  W.  Mill. 
Query  19.    What  is  the  best  formula  for  a  granular  effervescent 
Citrate  of  Magnesia,  which  shall  be  permanent,  readily  soluble  in  water 
and  suitable  for  general  use  ? 
Soluble  citrate  of  magnesia,  in  a  granular  form,  is  most  con- 
veniently obtained  according  to  the  writer's  experiments  by  the 
process  of  M.  de  Letter,  detailed  in  the  Am.  Jour.  Pharm.,  July, 
1863,  page  312.  To  succeed  well  the  ingredients  should  be  in- 
timately mixed  and  exposed  in  a  warm,  rather  moist  situation. 
The  reaction  is  completed  within  a  few  days,  and  the  resulting 
citrate,  by  simple  trituration  in  a  rnortar  and  sifting,  is  readily 
obtained  in  a  granular  condition. 
5 
