202 
ON  monsel's  salt. 
solutions,  from  which  there  is  deposited,  sometimes,  a  consider- 
able portion  undissolved. 
It  is  desirable  that  the  preparation  should  be  uniform  in  char- 
acter, so  that  the  purchaser  or  prescriber  in  ordering  it  could  be 
certain  to  get  a  pure  and  soluble  article,  instead  of  an  imperfect 
and  insoluble  one,  such  as  is  generally  furnished  at  the  present 
time. 
In  order  to  ascertain  if  the  salt  in  its  most  perfect  and  soluble 
condition  could  easily  be  made,  and  what  particulars  had  to  be 
observed  to  obtain  that  result,  I  made  a  few  experiments. 
The  formula  I  used  is  that  given  as  M.  Monsel's,  by  Prof. 
Procter,  in  the  American  Journal  of  Pharmacy,  (vol.  xxxi. 
p.  403.)  It  is  essentially  as  follows  : 
Take  of  Distilled  water  100  grammes 
Sulphuric  acid  (60°B.)  10  « 
Protosulphate  of  iron  100  « 
Nitric  acid  (35°B.)  16  « 
Mix  the  sulphuric  acid  and  water  in  a  pint  porcelain  capsule 
and  heat  to  ebullition  ;  dissolve  in  it  50  grammes  of  the  proto- 
sulphate of  iron  ;  add  the  nitric  acid  in  small  portions,  and 
when  the  evolution  of  the  nitric  oxide  has  ceased,  add  in  por- 
tions of  the  remaining  protosulphate  of  iron  previously  powdered. 
Boiling  should  be  continued  during  the  operation.  Lastly,  add 
sufficient  distilled  water  to  make  the  solution  measure  100  fluid 
grammes,  and  filter. 
In  the  first  experiments  made,  the  heat  applied  during  the 
oxidizement  of  the  protosulphate  of  iron  was  moderate.  It  was 
so  applied  as  to  not  volatilize  the  nitric  acid  before  it  could  be 
decomposed.  This  manner  of  operating,  however,  did  not  secure 
the  perfect  result  I  expected.  The  solutions  in  a  few  days  gave 
off  nitric  oxide,  and  the  salt  in  scales  prepared  from  them, 
though  fine  in  appearance  at  first,  became,  in  the  course  of  a 
week,  opaque,  and  gave  evidence  of  the  presence  of  nitric 
oxide. 
In  several  final  experiments,  I  maintained  the  heat  so  that  the 
solution  was  kept  generally  boiling  during  the  process,  and 
afterward  as  long  as  any  nitric  odor  was  perceptible.  The  nitric 
acid  when  added  to  the  boiling  solution  was  quickly  decomposed  ; 
none,  I  believe,  escaped  unchanged.    The  evolution  of  nitric 
