^'"■ffiSs.*''"''}       Mayer's  Reagent  for  Alkaloids.  495 
be  made  to  agree  quite  closely.  The  titrations  were  all  made  in  a  so- 
lution containing  one-tenth  per  cent,  by  volume  of  sulphuric  acid  and 
four  determinations  made  for  one  part  in  200  but  only  two  for  one  part 
in  500  which  agreeing  closely  gave  averages  respectively  of  O'OlOl 
and  0-0076. 
These  equivalents  are  considerably  lower  than  those  offered  by  Lyons, 
which  may  perhaps  be  accounted  for  by  the  difference  of  acidity  in  the 
solutions  titrated.  In  the  case  of  my  own  I  can  specify  the  exact 
amount  of  acid  used,  and  in  titrations  where  this  can  be  accurately  con- 
trolled the  equivalents  I  think  can  be  relied  on. 
If  this  acidity  is  not  under  control  I  should  be  inclined  to  doubt  the 
results  of  titrations.  The  mere  fact  that  two  observers  working  inde- 
pendently with  an  alkaloid  like  hydrastine  should  obtain  such  widely 
discrepant  results  shows  that  slight  variations  in  the  conditions  will 
affect  the  results.  The  acidity  seems  to  be  the  point  on  which  we 
must  have  differed.  As  already  stated,  my  titrations  were  made  in 
solutions  containing  one  per  cent,  sulphuric  acid.  The  four  determi- 
nations made  for  one  in  200  showed  respectively,  '0100,  '0100,  '0101 
and  '0102  while  for  one  in  500  the  titration  resulted  in  '0077  and 
•0075. 
The  precipitates  from  0*100  grammes  of  alkaloid  when  collected 
immediately  dried  and  weighed  averaged  0'206  grammes,  correspond- 
ing to  48J  per  cent,  alkaloid. 
Ordinarily  it  cannot  be  said  to  be  safe  to  determine  two  equivalents 
so  widely  separated  as  these  dilutions  were,  and  then  interpolate  in- 
termediate equivalents  for  reasons  which  will  be  readily  understood 
by  noting  the  equivalents  for  aconitine  or  berberine.  In  the  case  of 
hydrastine  however  it  seems  permissible  and  consequently  it  has  been 
followed  in  the  table. 
Fluid  measures  20  cc,  and  contains  2  cc,  of  1  per  cent,  by  volume  sulphuric 
acid. 
Cc.  required. 
Dilution. 
Jh:quivalent. 
5-26 
1  in  500 
•0076* 
5-81 
1  in  400 
•0086 
6-35 
1  in  350 
•0090 
7-09 
]  in  300 
•0094 
8-16 
1  in  250 
•0098 
0-90 
1  in  200 
•0101* 
