SOLUTION  OF  CITRATE  OF  MAGNESIA. 
171 
SOLUTIOJ^  OF  CITRATE  OP  MAGNESIA. 
By  R.  Rother. 
In  the  above  familiar  title  we  behold  the  officinal  synonym  for 
magnesium  citrate.  That  preparation,  therapeutically  so  much 
esteemed,  but  pharmaceutically  abhorred,  which  as  viewed  from 
the  officinal  stand-point,  deservedly  shares  the  aversion  enter- 
tained by  the  pharmaceutical  profession,  whilst  the  opprobrium 
cast  upon  it  is  justly  due  to  its  inconstancy  of  composition  and 
unstable  character — results  that  are  entirely  attributable  to  the 
fallacy  of  the  officinal  edict. 
Normal  magnesium  citrate  (Mg^'a  (CgH^O^)  2),  when  freshly 
prepared,  is  exceedingly  soluble  in  water,  but  in  moderately 
concentrated  solution  it  rapidly  undergoes  a  molecular  change, 
and  unites  with  seven  atoms  of  water  (Mg^'3  (CgH^O^)  2,  7  OH2). 
The  insoluble  combination  thus  produced  is,  consequently,  thrown 
out  of  solution.  But,  in  solutions  similar  to  the  officinal,  owing 
to  its  moderate  degree  of  dilution,  this  transformation  is  not  in- 
stantaneous, but  if  once  begun,  rapidly  progresses,  until  a  limit 
is  determined  by  the  presence  of  the  solvent ;  yet,  only  after 
the  greater  portion  of  the  magnesium  has  been  rendered  insolu- 
ble and  inert.  The  article  is  then,  of  course,  in  an  unsaleable  con- 
dition, and,  not  unfrequently,  a  serious  loss  to  the  conscientious 
pharmaceutist,  whose  integrity  led  him  to  misplace  his  confidence 
by  a  too  strict  adherence  to  the  officinal  code  ;  but  magnesium  cit- 
rate, in  this  condition,  is  by  no  means  a  loss,  since  application  of 
a  gentle  heat  again  restores  its  solubility.  The  solution,  after 
being  rebottled,  possesses  an  indefinite  permanence,  altogether 
similar  to  the  fresh  preparation. 
A  moderate  excess  of  acid  is,  also,  of  no  avail,  unless  it  be 
present  in  sufficient  quantity  to  form  the  bimetallic  salt  (Mg^' 
CgHgOjr),  which,  however,  is  not  the  intent  of  the  pharmacopoeia, 
for,  as  in  case  of  the  officinal  quantity,  if  the  magnesium  were 
reduced,  and  all  the  acid  retained,  an  immoderate  excess  of  this 
then  virtually  results,  which  would  not  fail  to  be  therapeutically 
objectionable. 
Knowing  that  the  officinal  formula  is  entirely  unsatisfactory, 
it  is  not  surprising  to  notice  a  rather  strong  disposition  to  dis- 
sent from  it,  and  in  the  absence  of  a  reliable  guide,  there  is  no- 
