Am.  Jour.  Pharm. 
May,  1886. 
Laboratory  Notes. 
235 
LABORATORY  XOTES. 
By  A.  H.  Cohn,  Ph.G. 
(Read  at  the  Pharmaceutical  Meeting,  April  20th.) 
Hydrargyri  Iodidum  Viride. — Having  an  opportunity  to  prepare 
mercurous  iodide  according  to  the  method  of  the  Pharmacopoeia, 
several  specimens  were  purchased  from  retail  pharmacists  and  tested 
for  mercuric  iodide. 
Three  samples  were  examined,  and  all  were  contaminated,  more  or 
less,  with  mercuric  iodide.  The  following  test  was  applied  to  detect 
the  mercuric  salt. 
A  definite  quantity  of  the  powder  was  shaken  with  alcohol.  The 
filtrate  was  evaporated  upon  a  watch  crystal  between  70°  and  80°  C. 
Specimen  1  contained  "5  per  cent,  of  mercuric  iodide. 
it  9         it  .o         u  a  it  a 
ii  g         u  .9         u  u  a  a 
The  specimen  prepared  by  myself  according  to  the  Pharmacopoeia 
contained  no  mercuric  salt.  No  doubt  most  mercurous  iodide  sold  in 
retail  stores  has  been  kept  for  some  time,  and  consequently  the  mer- 
curous iodide  is  changed  into  the  mercuric,  as  in  some,  places  I  noticed 
it  not  protected  from  the  light. 
Magnesii  Citras  G-ranuIatus. — Of  this  preparation  three  specimens 
of  different  manufacture  were  obtained,  and  all  were  found  to  be  con- 
taminated, more  or  less,  with  tartaric  acid.  The  following  are  some  of 
the  tests  given  by  the  Pharmacopoeia  : 
1.  On  addition  of  ammonium  chloride  to  the  aqueous  solution  of 
the  salt,  a  portion  of  the  liquid,  when  mixed  with  excess  of  solution 
of  ammonium  phosphate  and  water  of  ammonia,  should  produce  a 
white  crystalline  precipitate,  soluble  in  acids. 
2.  On  mixing  another  portion  with  test  solution  of  chloride  of 
calcium,  supersaturated  with  water  of  ammonia  and  filtering,  the  fil- 
trate deposits  a  white  precipitate  on  boiling. 
3.  The  saturated  aqueous  solution  of  the  salt,  when  mixed  with  a 
saturated  solution  of  potassium  acetate  and  some  acetic  acid,  should 
not  yield  a  white  crystalline  precipitate  (abs.  of  tartrate). 
The  first  test  was  answered  by  all  the  specimens.  Xone  of  the 
specimens  answered  the  second  and  third  tests.  The  third  test  given 
proved  that  there  was  tartaric  acid  in  all  of  them. 
