218     ON  THE  ACTIVE  PRINCIPLES  OF  THE  STRYCHNACE2E. 
iodine  or  f  are  absorbed  by  the  alkaloid,  and  there  is  consequently 
a  deficiency  of  f  of  the  number  of  cubic -centimetres  of  the  sil- 
ver solution  ;  i.  c,  to  precipitate  the  filtrate  from  the  mercurial 
precipitate  of  1  gramme  of  strychnia,  only  149*7  c.  c.  of  silver 
solution  are  required. 
A  gramme  of  pure  brucia  requires  42-9  c.  c.  of  mercurial  so- 
lution, and  the  composition  of  the  precipitate  is  analogous  to 
that  of  the  strychnia  compound,  and  to  that  of  the  combinations 
of  mercuric  chloride  with  strychnia  and  brucia.  It  is  also  ne- 
cessary that  the  brucia  solution  be  dilute  and  contain  no  more 
than  J  per  cent,  but  rather  less  of  the  alkaloid.  In  this  case 
there  will  consequently  be  a  deficiency  of  64-35  c.  c.  of  silver. 
Of  the  troy  weight  solution  of  iodide  of  mercury,  containing 
16  and  2-9th  grains  of  corrosive  sublimate  and  60  grains  of  iodide 
of  potassium  in  12J  troy-ounces,  every  10  grains  correspond  to 
0*0334  of  a  grain  of  strychnia,  and  0-0466  of  a  grain  of  crys- 
tallised brucia. 
With  these  data  the  subjoined  assays  have  been  made,  exhibit- 
ing the  relative  strength  of  the  officinal  preparations  from  nux 
vomica  and  ignatia  seed,  and  the  proportion  of  strychnia  and 
the  alkaloids  soluble  in  water  and  alkalies,  which  I  have  classed 
as  brucia. 
I.  Six  ounces  powdered  Nux  Vomica  exhausted  by  displacement 
with  SO  per  cent,  alcohol. 
The  tincture  was  evaporated  on  the  water-bath  with  a  little 
hydrochloric  acid  to  the  consistence  of  mellago.  While  still 
warm,  it  was  mixed  with  50  c.  c.  of  cold  water,  and  the  fatty 
substances  allowed  to  separate  by  standing ;  the  whole  was  then 
filtered,  and  with  the  washings  diluted  to  100  c.  c 
20  c.  c.  of  these  required  for  precipitation  21*5  c.  c.  of  mercu- 
rial solution ;  the  100  c.  c,  or  6  ounces,  therefore  107*5  c.c  Hg. 
20  c.c.  were  then  given  in  a  75  c.c  flask,  diluted  with  water  to 
75  c.c,  and  then  shaken  with  crystallized  caustic  baryta  in  ex- 
cess. After  filtering  the  alkaline  solution,  40  c.c.  of  it  was  acid- 
ulated with  hydrochloric  acid,  and  then  precipitated  by  the  mer^ 
curial  solution ;  they  required  10.3  c.c,  or  19-3  for  the  75  c.c. — 
20  c.c  original  solution.    These  75  c.c  hold  in  solution  strychnia 
