AmlpX5&arm"}  The  Reaction  of  Atropine  with  Mercurous  Salts.  199 
porated  left  but  a  shadowy  film.  These  tests,  which  I  have  since  con- 
firmed, show  that  when  atropine  is  digested  for  a  limited  time  with 
mercurous  chloride,  it  yields  a  mixture  of  mercurous  oxide  and  chlo- 
ride, and  that  no  atropine  enters  into  the  composition  of  the 
precipitate. 
My  attention  was  next  given  to  the  examination  of  the  filtrate  and 
washings  of  the  first  part  of  the  preceding  operations.  They  were 
strongly  alkaline,  and,  when  heated  to  remove  alcohol,  deposited  on 
cooling  some  fine  crystals,  which  proved  to  be  pure  atropine.  The 
liquor  from  which  the  crystals  had  been  removed  was  found  to  con- 
tain chlorides  and  combined  atropine,  mercury  was  absent.  This  was 
evidence  that  no  double  compound  of  the  mercurous  chloride  and 
atropine  had  been  formed,  as  is  the  case  with  mercuric  chloride  and 
atropine. 
Second  Experiment — It  was  made  to  ascertain  the  reaction  between 
atropine  and  a  soluble  mercurous  salt.  0*400  gm.  of  mercury  was 
dissolved  in  cold  nitric  acid  and  treated  with  atropine  in  excess;  the 
abundant  black  precipitate  which  formed  was  allowed  to  subside.  The 
decanted  solution  on  examination  was  found  to  consist  of  free  atropine 
and  nitrate  of  atropine,  mercury  was  absent.  The  black  precij>itate, 
carefully  washed  and  dried,  weighed  0*406  gm.  and  on  analysis  proved 
to  be  mercurous  oxide  with  a  small  portion  of  free  mercury ;  the  low 
yield — 0*406  instead  of  0*416  gm.  which  it  should  have  approximated 
to — is  to  be  accounted  for  by  the  ease  with  which  mercurous  oxide 
parts  with  its  oxygen  on  drying. 
The  second  experiment  is  quite  in  harmony  with  the  first,  differing 
only  in  the  completeness  of  the  reaction,  and  shows  the  change  to  be 
one  of  ordinary  double  decomposition.  I  find  that  the  reaction  with 
calomel  is  proportionate  to  the  length  of  time  it  is  subjected  to  warm 
digestion  with  the  atropine. 
It  was  particularly  noticed  in  the  second  experiment  that  a  con- 
siderable quantity  of  atropine  had  to  be  added  before  the  mercivrous 
salt  gave  a  precipitate.  Seeking  the  cause  of  this  I  found  it  due  to 
the  fact  that  mercurous  salts  diluted  with  water  yield  a  mixture  of 
acid  and  basic  salt,  and  the  acid  salt  must  be  neutralized  by  a  portion 
of  atropine  before  reduction  can  take  place.  This  property  of  mer- 
civrous salts  lessens,  to  some  extent,  the  delicacy  of  the  reaction,  and 
decreases  its  value  as  a  test;  but  I  find  large  dilution  is  in  a  great 
measure  a  remedy  for  the  acidity. 
