492  Mayer's  Reagent  for  Alkaloids.        {^'^' oT/im^''"'' 
BERBERINE 
Gives  very  favorable  results  on  titrations  with  Mayer's  reagent.  My 
own  results  for  titrations  in  dilutions  for  1  in  200, 1  in  400  and  1  in  600 
showed  an  equivalent  somewhat  smaller  than  that  found  by  Lyons; 
but  on  the  whole  I  prefer  to  accept  the  results  of  his  work/  and  the 
following  table  is  constructed  on  his  equivalents  : 
Fluid  measures,  40  cc.^  at  the  beginning  of  the  titration,  and  contains  6  cc.  of 
1  per  cent,  by  vol.,  sulphuric  acid. 
Cc.  required. 
Dilution. 
Equivalent. 
3-06 
1  in  600 
0-0218 
3-36 
1  in  500 
0-0238* 
3-57 
1  in  450 
00249* 
3-89 
1  in  400 
0-0257 
4-43 
1  in  350 
0-0258* 
5-13 
1  in  300 
0-0260* 
6-11 
1  in  250 
0-0262* 
76 
1  in  200 
0-0263 
BRUCINE. 
Titrations  of  this  alkaloid  are  far  from  satisfactory.    Results  are 
apt  to  vary  widely,  and  on  comparatively  little  provocation.    When  a 
series  of  equivalents  were  obtained  which  agreed  among  themselves 
the  following  were  the  figures : 
1  in  200   -01059 
1  in  300   -01025 
1  in  400   -01016 
It  will  be  seen  that  these  figures  differ  quite  materially  from  those 
of  previous  experimenters,  and  it  is  scarcely  worth  the  trouble  to  calcu- 
1  For  1  in  200,  1  in  400,  and  1  in  600, 1  found  1  cc.  of  the  reagent  to  precipi- 
tate, respectively,  0-0257,  0.0218  and  0-0186  of  alkaloid.  I  believed  at  the  time 
that  my  alkaloid  was  not  quite  pure,  and  in  this  case  the  presence  of  small 
amounts  of  hydrastine  would  lower  the  equivalent  considerably,  as  1  cc.  of 
the  reagent  will  precipitate  of  this  alkaloid  only  0*0101.  With  an  alkaloid 
giving  as  good  results  as  berberine  is  reported  and  seems  to  give,  it  is  likely  that 
the  highest  equivalent  obtained  would  be  the  most  nearly  correct. 
^  In  applying  Mayer's  agent  to  hydrastis  probably  a  dilution  of  20  cc,  repre- 
senting 2^  grammes  of  drug,  would  be  better  than  40  cc;  but  in  this  case  titra- 
tion give  at  best  only  a  rough  idea  of  the  value  of  the  drug,  and  can  hardly  be 
regarded  as  having  comparative  value,  owing  to  the  wide  difference  between  the 
titration  equivalents  of  hydrastine  and  berberine.  Here  we  must  be  content  to 
state  results  as  "  so  many  "  cc.  of  reagent  to  each  gramme  of  drug,  or  cc.  of 
fluid  extract. 
