116  Ferric  Citrate  and  its  Double  Salts.  {^'^M^r^'ils^!''"^ 
baric  sulphate,  which  corresponds  to  0'2423  gm.  of  strychnine  sulphate,, 
and  when  further  calculated  as  above,  gives  the  number  of  parts  of 
water,  in  which  the  salt  is  soluble,  or  42' 67  parts. 
According  to  Rammelsberg,  neutral  strychnine  sulphate  becomes 
anhydrous  at  200°C.  The  United  States  Pharmacopoeia  states,  that, 
when  heated  to  a  temperature  of  135°C.,  it  first  melts,  and  then  looses 
its  water  of  crystallization.  On  heating  portions  of  sulphate  of  strych- 
nine in  an  air-bath,  I  found  that  the  salt  became  anhydrous,  without 
melting,  at  185°C.,  and  when  heated  in  a  capillary  glass  tube,  in  a 
bath  of  sulphuric  acid,  it  assumed  a  very  dark-brown  color  at  225°C., 
and  was  evidently  decomposed,  without,  however,  at  this  temperature 
showing  any  indication  of  fusion.  As  seen  by  these  experiments, 
strychnine  sulphate  of  American  manufacturers  is  distrychnine  sulphate 
having  the  formula  (C2iH22NA)2H2SO,4-6H20.  It  is  soluble  in  from 
42  to  43  parts  of  water  at  15°C.  It  becomes  anhydrous  at  185°C.,, 
without  fusion,  losing  from  12*099  per  cent,  to  12*5  per  cent,  of  its- 
weight,  and  is  decomposed  at  a  temperature  of  about  225°C. 
FEKRIC  CTTl^ATE  AND  ITS  DOUBLE  AND  SECONDARY 
SALTS. 
By  R.  Rother. 
It  was  formerly  nuich  more  the  practice  than  now,  in  writing  the- 
formulas  of  ordinary  chemicals,  to  omit  the  water  not  belonging  to  the 
characteristic  part  of  the  compound.  At  that  early  period  this  approx- 
imate degree  of  accuracy  was  perhaps  all  sufficient.  ^  But  since  phar- 
macists have  been  drawn  nearer  to  chemistry  by  reason  of  the  great 
development  of  this  important  part  of  their  business,  it  has  become 
necessary  to  insist  upon  a  more  complete  notation.  These  imperfect 
formulas  were  largely  transcribed  into  the  text-books  of  pharmacy  and 
generally  passed  current  as  the  whole  expression  for  the  respective 
compounds.  Many  erroneous  processes  and  false  results  were  the  con- 
sequence of  thus  relying  upon  what  was  deemed  authoritative.  Ferric 
citrate  is  an  excellent  illustration  of  such  cases.  The  chemical  formula 
of  this  salt  was  invariably  given  as  FeCgHgO^  or  Fe  Ci.  Considering 
this  formula  to  be  accurate  and  complete,  the  writer  some  years  since 
attempted  to  determine  the  constitution  of  the  official  so-called  ammo- 
nio  citrate  of  iron.  The  result  obtained  apparently  indicated  that  the 
ammonia  was  absorbed  in  the  proportion  to  form  normal  ammonium 
