ON  SOLUBLE  CITRATE  OF  MAGNESIA. 
407 
the  formula  it  will  be  easy  to  get  a  salt  neutral  in  composition 
and  free  from  NO5  which  will  replace  the  salt  of  Monsel  in  all 
respects  as  a  coagulative  astringent.  At  a  more  convenient 
season  the  writer  proposes  to  return  to  this  subject,  and  by  the 
aid  of  his  medical  friends  have  ascertained  by  adequate  trials 
the  relative  efficiency  of  the  regular  and  of  Monsel's  sulphate  in 
surgical  practice. 
SOLUBLE  CITRATE  OF  MAGNESIA. 
It  is  undoubtedly  a  desideratum  to  get  a  solid  Citrate  of  Mag- 
nesia that  is  soluble  in  water  and  may  be  used  when  required 
in  graduated  doses.  It  is  well  known  that  Dorvault  and  others 
have  published  formulae  for  producing  such  a  preparation. 
All  seem  to  unite  in  the  conclusion  that  it  is  necessary,  in 
order  to  get  a  soluble  citrate,  to  unite  the  magnesia  with  the 
citric  acid  through  the  agency  of  its  water  of  crystallization 
only,  as  where  the  salt  is  in  presence  of  an  excess  of  water  it 
appropriates  sufficient  to  make  the  crystalline  tribasic  salt  with 
14  equivalents  of  water,  too  insoluble  for  use. 
It  is  also  well  known  that  Solution  of  Citrate  of  Magnesia  is 
often  found  to  be  unpleasantly  acid,  the  excess  being  greater 
than  is  desirable  for  controlling  the  magnesian  taste.  A  well 
prepared  solution  leaves  nothing  to  be  desired  except  its  in- 
eligibility for  transportation  by  travellers,  and  its  liability 
change  by  keeping.  It  is  well,  therefore,  whilst  retaining  this  ex- 
cellent preparation,  to  aim  at  perfecting  the  solid  citrate,  so  that 
it  will  afford  a  good  substitute  for  the  solution  for  travellers  and 
others.  These  remarks  have  been  called  forth  by  the  following 
letter  to  the  Editor. 
Richmond,  Indiana,  July  18,  1859. 
Respected  Friend, — My  almost  forgotten  promise  to  send  a 
sample  of  our  "  Soluble  Citrate  of  Magnesia"  was  called  to  mind  a 
day  or  two  since,  and  I  now  send  two  packages ;  they  are  taken 
from  a  lot  made  for  our  regular  custom,  and  differ  in  no  wise 
from  that  always  made.  We  have  kept  them  as  long  as  four 
months,  in  which  time  the  powder  appears  to  cake,  but  is  easily 
broken  up,  when  it  dissolves  as  readily  as  ever,  and  produces  as 
full  cathartic  effect  as  the  fresh.  We  have  made  and  sold  them 
for  eighteen  months  or  more,  and  the  demand  is  larger  now 
