Am.  jour.  Pharm. ) 
Oct.,  1885.  ! 
Alkaloids  of  Coca  Leaves. 
473 
derivative.  Other  acids  besides  the  hydrochloric  develop  it  under 
similar  conditions. 
The  behavior  of  solutions  of  pure  cocaine  muriate  with  the  common 
reagents  has  been  studied  by  the  writer  with  the  following  results : 
Mayer's  reagent  is  capable  of  detecting  very  minute  quantities  of 
the  alkaloid.  A  single  drop  of  a  solution  containing  one  part  of  the 
salt  in  12,500  parts  of  water  yields  with  this  reagent  a  distinct  preci- 
pitate. A  faint  cloud  is  produced  in  a  solution,  1 : 100,000 ;  in  one  of 
half  this  strength  it  is  barely  discernible,  a  single  drop  of  the  solution 
placed  on  a  mirror  being  employed  in  this  as  in  the  other  tests  men- 
tioned. 
In  solutions  containing  one  part  of  alkaloid  in  500,  one  Cc.  of  Mayer's 
reagent  corresponds  with  ten  milligrams  of  alkaloid ;  in  solutions  of 
double  this  strength,  one  Cc.  of  reagent  consumed  indicates  12*5  milli- 
grams of  alkaloid,  while  in  solutions  twice  as  strong  again  (1 : 125)  one 
Cc.  of  the  reagent  indicates  15  milligrams  of  cocaine.  In  estimating 
the  strength  of  a  solution  volumetrically,  therefore,  by  this  reagent,  it 
is  necessary  to  obtain  in  a  preliminary  experiment  a  rough  approxima- 
tion to  the  result,  and  then,  having  diluted  the  solution  so  that  it  shall 
contain  nearly  one  part  of  alkaloid  in  500,  to  make  a  second,  more 
-careful  experiment;  but  this  is  true,  to  a  greater  or  less  degree,  of  all 
titrations  with  Mayer's  reagent. 
A  solution  of  iodine  in  iodide  of  potassium  produces  in  a  solution 
containing  1 :  7,500  of  cocaine  hydrochlorate  a  pinkish  precipitate  ;  in 
stronger  solutions  the  precipitate  appears  brown.  A  faint  yellowish 
cloud  is  produced  in  solution  1 : 200,000 ;  barely  perceptible  in  a  solu- 
tion 1 : 400,000. 
Phosphomolybdic  acid  produces  a  faint  turbidity  in  a  solution 
1 :  50,000,  and  a  distinct  precipitate  in  one  1 : 12,500. 
Tannin  produces  a  faint  cloud  in  solutions  1 : 25,000  (neutral) ;  a 
-distinct  precipitate  in  solutions  1 : 12,500. 
Picric  acid  produces  in  strong  solutions  a  yellow  precipitate,  which 
assumes  crystalline  form.  In  solutions  1 :400  the  precipitate  is  thrown 
down  at  once,  appearing  under  the  microscope  in  sheaf-like  forms.  In 
solutions  1 : 1,000  a  few  crystals  may  be  found,  appearing  after  the  lapse 
of  some  minutes. 
Potassium  bidiromate  precipitates  only  strong  solutions  (1 :  25),  the 
precipitate  being  amor[)hous  or  yellow. 
Mercuric  chloride  produces  a  white  amorphous  precipitate  in  solu- 
itions  1:100,  none  in  solutions  of  half  that  strength. 
