252 
FERRI  ET  STRYCHNIiE  CITRAS. 
add  this  also  to  the  heated  liquid.  Mix  thoroughly,  and  allow 
the  solution  to  stand  twenty-four  hours.  Then  filter,  evaporate 
on  a  water-buth,  at  a  temperature  below  150°,  to  a  syrupy  con- 
sistence, spread  on  plates  of  glass,  and  dry  in  an  atmosphere 
heated  to  about  90°. 
The  salt  thus  prepared  is  in  garnet-red,  translucent  scales, 
soluble  in  water  in  all  proportions  ;  it  contains  one  per  cent,  of 
strychnia,  this  being  considered  the  most  appropriate  strength 
in  consideration  of  the  relative  doses  of  the  alkaloid,  and  the 
iron  salt. 
The  method  of  assay  to  determine  the  proportionate  amount 
of  strychnia,  is  advised  to  insure  accuracy  and  uniformity.  The 
formula  has  been  used  by  the  writer  for  several  years  and  has 
always  yielded  a  satisfactory  product.  In  experimenting  upon 
this  salt  it  was  found  that  the  citrate  of  strychina  was  liable  to 
crystallize  from  solutions  containing  an  excess  of  acid ;  a  solution 
of  citrate  of  iron,  not  quite  neutralized  with  ammonia,  deposited 
almost  the  entire  amount  of  the  alkaloid  upon  standing  twenty- 
four  hours.  It  appeared  in  cubical  crystals,  slightly  colored. 
The  writer  believes  it  to  be  essential  to  the  successful  use  of  this 
formula,  that  the  iron  solution  be  exactly  neutralized^  an  excess 
of  alkali  being  equally  inadmissible.  Litmus  paper  moistened, 
dipped  into  the  liquid,  and  afterwards  washed  with  distilled 
water,  gives  accurate  indications ;  fresh  pieces  of  paper  should 
be  employed  in  every  repetition  of  the  test. 
In  the  experience  of  the  writer  the  citrate  of  strychnia  will 
never  separate  from  a  neutral  solution  of  citrate  of  iron  and  am- 
monia. If  such  an  occurrence  be  possible,  it  will  be  made  evi- 
dent during  the  twenty-four  hours  intervening  between  the  for- 
mation of  the  solution  and  its  filtration  ;  and  it  is  with  this  object 
that  the  interval  is  prescribed. 
The  citrate  of  iron  and  strychnia  is  very  deliquescent,  and 
will  not  dry  and  scale  properly  if  the  atmosphere  be  very  humid  ; 
accordingly,  it  is  difiicult  to  prepare  this  salt  during  the  summer 
months  ;  in  winter  it  dessicates  without  the  slightest  difl&culty. 
It  is  advisable  to  warm  the  under  sides  of  the  glass  before  at- 
tempting the  removal  of  the  salt ;  the  heat  thus  applied  has  the 
effect  of  loosening  it  from  the  glass,  and  enables  the  operator  to 
