Am.  Jour.  Pharm.  1 
Oct.,  1882.  j 
Commercial  Potassium  Bromide. 
483 
remained  permanent.  Each  cubic  centimeter  of  the  silver  solution 
being  equivalent  to  '0145  gram  of  ammonium  iodide,  the  amount  of 
pure  iodide  was  readily  calculated.    The  results  were  as  follows  : 
Weight  of  salt,  gm   -0068      -1795      -1905     '0886      -2335      '123      -2045      -2451  -310 
V^ol.  solution,  cc   4*6       12-35      12-5       6-1       15-8  8*2      14-         16*6  21'3 
-Pr.ct.  of  Am  I,  airdry  99-83    ,  99-76      95-14     99*83      98.11  96-666   99-26      98-20  99-629 
"        "      atllO°C.  99-907   100-       100-      100-       100'  99-675  100*       100-  100- 
COMMERCIAL  POTASSIUM  BROMIDE. 
By  Jui^ius  Way,  Ph.G. 
From  an  Inaugural  Essay. 
When  pure,  potassium  bromide  crystallizes  in  the  monometric  or 
Tegular  system,  some  of  the  crystals  forming  nearly  perfect  cubes  which 
are  colorless,  but  as  met  with  in  commerce  they  are  white,  owing  to 
the  presence  of  a  trace  of  carbonate.  They  closely  resemble  the 
•crystals  of  potassium  iodide,  but  are  entirely  destitute  of  odor.  The 
taste  is  pungent  and  saline,  but  much  more  agreeable  than  that  of  the 
iodide.  Potassium  bromide  is  freely  soluble  in  water,  and  sparingly 
soluble  in  alcohol,  requiring  lor  solution  about  200  parts  of  the  latter 
solvent. 
Commercial  potassium  bromide  is  always  contaminated  with  chloride, 
it  being  impossible  to  entirely  free  the  bromine,  from  which  it  is 
prepared,  from  chlorine  without  increasing  the  cost  of  the  former  to  a 
considerable  extent.  Owing  to  this  fact  about  2  per  cent,  of  chloride 
must  usually  be  admitted  in  the  commercial  salt.  Ten  samples  were 
obtained  from  different  sources  and  carefully  analyzed  to  determine  the 
presence  of  impurities.  The  aqueous  solution  tested  with  litmus  was 
found  in  every  case  to  have  an  alkaline  reaction. 
The  salts  were  then  qualitatively  analyzed.  All  the  samples  were 
found  to  contain  chloride,  six  a  small  amount  of  sulphate  and  one 
carbonate  of  potassium.  No  metallic  impurities  were  present  in  either 
of  the  samples. 
The  amout  of  chloride  in  each  sample  was  volumetrically  estimated 
by  means  of  a  decinormal  solution  of  argentic  nitrate,  using  potassium 
chromate  as  an  indicator.  The  manner  of  determining  the  percentage 
of  chloride  was  as  follows : 
A  definite  quantity  of  the  salt  was  dissolved  in  distilled  water  auH 
the  solution  of  argentic  nitrate  gradually  added  from  a  burette  until 
the  salt  was  completely  precipitated,  and  the  amount  of  silver  solution 
