482  Ammonhwi  Iodide.  { ^°'oct"'"ir82*™" 
myrrh.  When  the  liquor  is  mixed  with  olive  oil,  if  the  oil  be  pure 
no  such  change  takes  place.  Noticing  this  change,  it  occurred  to  me 
that  this  would  be  a  simple  and  easy  way  to  detect  cotton  seed  oil 
when  mixed  with  olive  oil.  This  change  usually  takes  place  after 
standing  from  twelve  to  twenty -four  hours.  It  is  easily  detected  in 
mixtures  containing  five  per  cent,  or  even  less  of  the  oil,  and  I  am 
convinced,  after  making  numerous  experiments  with  different  oils,  that 
it  is  peculiar  to  cotton  seed  oil. 
Charlestown^  Mass.,  September,  1882. 
AMMONIUM  IODIDE. 
By  John  A.  Lambert,  Ph.G. 
From  an  Inaugural  Essay. 
The  author  discusses  the  various  methods  which  have  been  proposed 
and  arrives  at  the  conclusion  that  acceptable  results  are  obtained  by 
the  process  adopted  by  the  U.  S.  Pharmacopoeia  of  1870,  provided  the 
error  be  corrected  in  the  relative  proportion  of  potassium  iodide  and 
ammonium  sulphate,  so  that  for  332  parts  of  the  former  132  parts  of 
the  latter  salt  are  used.    It  is  further  suggested  that  the  salts  be  dis- 
solved separately  in  cold  instead  of  boiling  water,  and  that  in  the 
evaporation  to  dryness  the  liquid  be  kept  alkaline  by  the  occasional 
addition  of  ammonia ;  with  these  modifications  the  process  will  yield 
an  uncolored  salt,  which,  however  is  more  deliquescent  and  more 
readily  decomposed  on  exposure  than  the  salt  prepared  frojn  pure 
hydriodic  acid  and  ammonia.    Made  by  the  latter  process,  the  salt 
will  cost  about  50  per  cent,  more  than  when  prepared  by  the  modified 
officinal  formula ;  it  is  then  white  and  granular,  and  on  exposing  small 
quantities  for  one  or  two  weeks  in  a  rather  moist  atmosj)here,  they 
remained  dry  and  only  began  to  show  signs  of  deliquescence  at  the  end 
of  that  time. 
Ten  commercial  samples  of  ammonium  iodide  were  procured  in  dif- 
ferent parts  of  the  country  for  examination.  One  of  these  samples 
contained  '085  per  cent,  of  free  iodine.  The  remaining  nine  samples 
were  tested  qualitatively  and  the  amount  of  ammonium  iodide  esti- 
mated by  decinormal  solution  of  nitrate  of  silver,  using  chromate  of 
potassium  as  an  indicator.  A  definite  quantity  of  the  salt  was  dis- 
solved in  distilled  water,  a  little  chromate  was  added,  and  the  liquid 
precipitated  by  the  volumetric  solution   until   a  slight  red  color 
