498 
Commercial  Iodide  of  Potassium,. 
f  Am.  Jour.  Pharm 
1       Oct.,  1883 
Germ.'^  From  the  labels,  then,  it  is  to  be  understood  that  all  the 
articles  represented  in  these  samples  were  pat  forth,  alike  for  medicinal 
use — the  ordinary  use  of  iodide  of  potassium — and  without  claim  for 
any  higher  degree  of  purity  than  medicinal  uses  (or  pharmacopoeial 
specifications)  require.  The  price-lists  of  the  German  makers  of  pure 
chemicals  for  analytical  and  special  purposes,  usually  give  two  grades 
of  "  Kalium  iodatum,''  namely:  "Ph.  Germ,''  and  "  pur  iss./' the 
latter  article  being  priced  only  three  or  four  per  cent,  higher  than  the 
former.  It  is  true  that  the  article  professing  to  be  merely  German 
pharmacopoeial  iodide  of  potassium  is  frequently  furnished  and  used^ 
in  this  country,  as  a  "  chemically  pure ''  salt  for  analytical  purposes.  > 
And  from  occasional  trials  of  both  these  German  grades,  during  the 
past  six  or  eight  years,  I  can  only  say  that  the  article  marked  " purissi- 
mum^^  is  somewhat  more  likely  to  be  fit  for  all  uses  of  a  chemical 
reagent  than  the  article  marked  "Ph.  German./'  while  even  the  former 
is  often  defective.  Under  the  imprint  "|)itms."  I  have  less  often 
found  an  alkaline  reaction,  or  the  presence  of  iodate,  but  have  fre- 
quently found  chloride  and  not  rarely  bromide.  An  article  trust- 
worthy as  a  reagent  in  all  uses,  can  only  be  obtained,  already  made, 
out  of  these  grades,  by  selection  of  lots,  upon  special  order.  And 
cheaper  grades  than  either  of  these  are  to  some  extent  available  for 
analytical  uses,  by  careful  selection,  it  being  not  very  uncommon  to 
find  a  lot  of  American  medicinal  iodide  of  potassium  that  is  at  once 
neutral  in  reaction,  and  free  from  appreciable  traces  of  iodate,  chloride, 
bromide  and  sulphate.  In  view  of  their  cost  in  this  country,  it  may 
well  be  claimed  that  the  European  articles  represented  in  these  samples 
are  not  in  the  market  upon  the  same  plane  with  the  American  articles.^ 
Nevertheless  we  have  to  note  that  these  European  grades  are  made  for 
medicinal  use  in  Europe. 
The  Query  concerns  only  conformity  to  the  test-limits  of  the  Phar- 
macopoeia.   Our  standard  of  measurement  is  the  United  States  Phar- 
^  With  present  import  duties  it  appears  that  the  cost  of  the  European 
goods  under  consideration  is  about  100  per  cent,  greater  than  that  of  the 
American  goods,  each  being  carried  in  the  same  quantities.  Sold  as  special 
goods  upon  small  demand,  the  European  articles  cost  from  130  to  150  per 
cent,  more  than  the  American.  In  a  late  instance  known  to  the  writer, 
iodide  of  potassium  warranted  chemically  pure  for  use  in  analysis,  and 
admissible  to  the  country  free  of  duty  for  scientific  purposes,  was  obtained 
by  importation  at  a  rate  thirty-three  per  cent,  higher  than  the  rate  for  the 
standard  medicinal  salt  of  American  manufacture. 
