ON  THE  ACTIVE  PRINCIPLES  OF  THE  STRYCHNACEiE.  217 
earths,  and  determines  the  quantity  of  brucia  in  the  alkaline 
mother  liquor  from  the  precipitation  of  strychnia  by  acidulating 
and  then  precipitating  it  with  corrosive  sublimate. 
It  might  be  supposed  that,  as  this  solubility  is  considered  a 
characteristic  of  igasuria  solely,  this  alkaloid  or  mixture  of  al- 
kaloids was  identical  with  brucia,  and  that  there  were  in  fact  but 
two  alkaloids  present  in  the  plants  of  one  family.  But  there  is 
a  considerble  degree  in  this  solubility  ;  a  portion  of  the  dissolved 
alkaloid  crystallises  out,  while  the  remainder,  which  however 
forms  a  crystalline  salt  with  oxalic  acid,  is  held  indefinitely  long 
in  solution. 
Strychnia  itself  is,  to  some  extent,  soluble  in  alkaline  liquids. 
As  the  proper  alkali  for  experiments  and  assays  of  this  kind,  I 
have  long  since  used  and  lately  recommended  in  a  particular  in- 
stance, crystallised  caustic  baryta,  which,  in  my  opinion,  cannot 
be  surpassed  by  any  other  substance  of  this  class.  My  remarks 
in  this  connection  have  therefore  exclusive  reference  to  precipita- 
tion and  solution  by  means  of  caustic  baryta. 
One  hundred  c.  c.  of  a  solution  of  baryta  at  60°F.  dissolve 
0-036  of  a  gramme,  or  0*55  of  a  grain  of  strychnia.  ■ 
One  hundred  c.c  of  the  same  solution  of  baryta  dissolve  as  a 
minimum  0*5  grammes,  or  nearly  8  grains  of  brucia. 
In  determining  the  strength  of  a  preparation  from  a  drug  con- 
taining these  alkaloids,  it  is  only  necessary  to  know  the  quantity 
of  a  reagent  required  for  the  sum  of  the  alkaloids,  to  precipitate 
a  known  portion  of  the  solution  made  from  the  preparation  by 
baryta,  and  to  dilute  the  alkaline  liquor  to  a  certain  strength  suf- 
ficient to  hold  in  solution  all  the  brucia  which  may  be  present. 
A  gramme  of  pure  strychnia  requires  for  precipitation  59-88 
c.  c.  of  l-10th  normal  solution  of  iodide  of  mercury,  provided 
the  strength  of  the  solution  does  not  exceed  J  of  one  per  cent. 
The  precipitate  produced  differs  in  its  composition  from  that 
yielded  by  other  alkaloids,  inasmuch  as  it  contains  2  eq.  of 
mercuric  iodide  to  one  of  hydriodate  of  the  alkaloid.  The  quan- 
tity of  l-10th  normal  silver  solution  equivalent  to  59-88  c.  c.  of 
mercury  solution  is  239.52  c.c. ;  of  the  8  equivalents  of  iodine 
and  chlorine  contained  in  the  59-88  c.  c.  mercurial  solution,  3  of 
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