304  Alkaloidal  Assay.  { Am  jJu^9p0?arm- 
alcoholic  solution  of  ammonium  acetate  excess  of  that  acid  was 
added.  Bitartrate  of  ammonium  was  immediately  precipitated  in 
a  fine  granular  form  easily  retained  by  cotton  wool.  Nessleriztng 
showed  o- oooo I  gramme  of  NH3  per  cubic  centimeter  of  the  filtrate. 
Tartaric  acid  in  excess  and  sulphuric  acid  q.  s.  are  therefore  equally 
effective  precipitants  of  NH3  from  alcoholic  solution,  other  con- 
siderations must  determine  the  choice  ;  the  modifying  effect  of  the 
faintest  excess  of  sulphuric  acid  has  already  been  pointed  out  and 
the  difficulty  of  preventing  its  occurrence  was  found  to  be  practi- 
cally insurmountable.  Apart  from  the  defeat  of  the  original  object 
in  view,  the  presence  of  free  sulphuric  acid  might  injure  alkaloids  of 
delicate  structure  in  any  subsequent  evaporation  of  the  alcohol. 
Its  use  was  therefore  discarded  in  favor  of  tartaric  acid  which  offered 
none  of  these  objections. 
There  remained  the  question  of  the  solubility  of  the  alkaloids  in 
strong  alcohol  containing  excess  of  tartaric  acid.  Tanner1  calls 
attention  to  the  formation  of  an  acid  tartrate  of  morphine  which  is 
nearly  insoluble  in  alcohol.  Subsequent  communications2  from 
Dott  and  Rutherford  Hill  on  the  subject  give  expression  to  the 
opinion  that  alkaloids  generally  form  sparingly  soluble  acid  tartrates 
analogous  to  the  ammonium  salt.  This  is  correct  so  far  as  it 
goes.  When  alcoholic  solution  of  morphine,  for  instance,  is  neutral- 
ized by  a  solution  of  tartaric  acid  in  the  same  medium,  part  of  the 
alkaloids  is  precipitated  as  neutral  tartrate ;  and  on  again  adding  a 
similar  volume  of  the  tartaric  acid  solution  the  mixture  becomes 
pasty  from  the  total  precipitation  of  the  acid  tartrate  of  morphine. 
The  analogy  with  ammonia,  however,  ends  at  that  point,  since  on 
the  addition  of  a  further  portion  of  the  tartaric  acid  solution,  or  even 
a  little  powdered  tartaric  acid,  the  precipitated  acid  tartrate  is 
completely  dissolved. 
Experiments  with  other  alkaloids  led  to  the  conclusion  that 
alkaloidal  acid  tartrates  are  soluble  in  the  presence  of  excess  of 
tartaric  acid. 
This  behavior  of  the  alkaloidal  acid  tartrates  is  not  mentioned  in 
any  journal  or  reference  book  to  which  I  have  access.  It  may, 
therefore,  at  least,  be  assumed  that  the  phenomenon  is  not  so  well 
known  as  that  of  their  insolubility. 
On  adding  then  a  fluid  extract  to  a  large  bulk  of  absolute  alcohol 
1  Phar.  Journ.,  Jan.  31,  1903,  134. 
2  Phar.  Journ.,  Feb.  7,  1903,  178. 
