ASSAY  OF  ALKALOIDS. 
15 
II.  Cinchonia. 
Mr.  Groves'  formula 
Cin+HI+2HgI. 
My  formula. 
2Cin+3HI+5HgL 
Cinchonia 
HI 
2HgI 
313. 
128. 
454. 
895. 
3  HI 
5HgI 
626. 
384. 
1135. 
2145. 
In  100  parts: 
By  his  formula.        His  analysis. 
Cinchonia  (+H)  35-09.  28-56. 
Iodine  42-57.  4745. 
Mercury  22-34.  23-99. 
My  formula. 
*  29-47. 
47-22. 
23-31. 
100-00     100-00  100-00 
His  assay,  altogether  owing  to  dilution,  differs  from  mine  as 
190  to  156. 
I  cannot  conclude  this  paper  without  some  words  about 
Mr.  Groves'  strictures  with  reference  to  my  method  in  analys- 
ing extracts.  As  I  have  never  pretended  to  determine  the 
separate  quantity  of  alkaloids  until  I  had  really  eliminated 
them,  and  since  I  have  never  analysed  a  juice  or  extract  with- 
out previously  acidulating  it,  I  cannot  perceive  the  drift  of  some 
of  them.  There  is  one  instance  in  which  he  apparently  contra- 
dicts a  statement  of  mine  about  the  precipitation  of  albumen 
by  my  reagent.  I  said  two  years  ago  that  the  precipitation  is 
not  interfered  with  by  the  usual  constituents  of  pharmaceutical 
preparations,  except  alcohol  and  acetic  acid,  and  that  not  even 
albumen  caused  a  disturbance.  I  had  previously  ascertained 
that  a  strong  solution  of  this  substance  remained  perfectly  clear 
upon  the  addition  of  iodohydrargyrate  of  potassium,  and  that 
its  precipitate  by  corrosive  sublimate  was  redissolved  by  iodide 
of  potassium.  I  may  now  add  that  under  ordinary  circumstan- 
ces no  precipitation  of  albumen  is  caused  by  the  reagent  in  watery 
solutions  of  extracts,  unless  they  contain  a  very  large  excess  of 
mineral  acid.  All  such  minute  quantities  of  albumen  are  like- 
wise precipitated  by  chloride  of  mercury,  and  there  is  no  ob- 
