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Detection  of  Silver  Salts. 
|  Am.  Jour.  Pharm. 
(.       Dec,  1890. 
NOTES  ON  THE  DETECTION  OF  SILVER  SALTS  IN 
SOLUTIONS  CONTAINING  MERCUROU5  SALTS. 
By  Frank  X.  Moerk,  Ph.G. 
Contribution  from  the  Chemical  Laboratory  of  the  Philadelphia  College  of  Pharmacy. — 
No.  82. 
The  method  of  detection  of  these  two  salts  in  qualitative  analysis 
depends  upon  the  precipitation  first  of  the  chlorides  by  hydrochloric 
acid  and  then  treating  the  washed  chlorides  upon  the  filter  with 
water  of  ammonia,  the  mercurous  salt  being  indicated  by  a  blacken- 
ing of  the  precipitate,  while  the  silver  chloride  dissolves  and  is 
reprecipitated  by  addition  of  nitric  acid.  If  the  black  residue  rep- 
resenting the  mercurous  salt  be  heated  with  nitric  acid,  the  mer- 
curous salt  is  converted  into  mercuric  salt  which,  after  diluting  with 
water,  is  not  precipitated  by  addition  of  hydrochloric  acid. 
Examining  a  solution  containing  about  one  per  cent,  of  silver  nitrate 
with  mercurous  nitrate,  it  was  found  that  after  acidifying  the  am- 
monia solution  with  nitric  acid,  only  the  faintest  turbidity  was  pro- 
duced, whereas  from  a  one  per  cent,  silver  nitrate  solution  could  be 
expected  a  copious  precipitate  ;  it  did  not  matter  how  often  the 
ammonia  solution  was  returned  to  the  filter  and  allowed  to  run 
through  again,  the  turbidity  of  the  acidified  solution  was  not  per- 
ceptibly increased,  nor  did  loosening  the  precipitate  from  the  sides 
of  the  filter  alter  the  result.  Boiling  the  residue  of  the  ammonia 
treatment  with  nitric  acid  for  several  minutes,  diluting  with  water 
and  adding  a  little  dilute  hydrochloric  acid  gave  a  decided  precipi- 
tate, which,  collected  upon  a  filter  after  washing,  was  easily  soluble 
in  ammonia  and  then  reprecipitated  by  addition  of  nitric  acid. 
The  probable  cause  is  that  the  precipitated  mercurous  chloride 
surrounds  the  precipitated  silver  chloride  and  prevents  the  solvent 
action  of  the  ammonia. 
A  solution  containing  silver  nitrate,  lead  nitrate  and  mercurous 
nitrate  was  found  to  give  the  test  for  silver  without  the  above  diffi- 
culty. 
Further  experiments  will  be  made  to  ascertain  the  proportions  of 
the  two  salts  necessary  to  give  the  above  results. 
Bromoform  has  been  used  in  whooping  cough  by  Dr.  Neumann  (see  also 
this  volume  pp.  89  and  405)  in  doses  of  3  to  5  drops,  suspended  in  syrup,  and 
frequently  repeated.  It  reduces  the  number  of  paroxysms  and  appears  to  cut 
short  the  disease.  —  Therap.  Monatsh.,  July,  1890. 
