AMjuneBiPmr  )    Iodide  and  Bromide  of  Ammonium.  249 
monia,  I  subjected  "a"  to  the  influence  of  ammonia  for  several  days, 
but  observed  no  change.  Obtained  as  above  described,  "6"  exists  in 
Hydrastis  Canadensis  in  less  quantity  than  hydrastia. 
The  ultimate  contents  of  "5"  I  have  not  yet  had  time  to  determine. 
Ann  Arbor,  Mich.,  May  10th,  1873. 
IODIDE  AND  BROMIDE  OF  AMMONIUM. 
By  Charles  Rice. 
The  process  adopted  in  the  last  Pharmacopoeia  for  the  preparation 
of  iodide  of  ammonium  was  published  several  years  ago  in  the  Pro- 
ceedings of  the  American  Pharmaceutical  Association  (1866),  and  in 
the  American  Journal  of  Pharmacy  (1867),  and  no  doubt  yields  an 
excellent  product,  although  the  latter  is  contaminated  with  a  minute 
proportion  of  sulphate  of  potassa.  But  the  quantities  of  iodide  of 
potassium  and  of  sulphate  of  ammonia,  which  the  Pharmacopoeia 
directs  to  be  used,  are  not  correct.  Four  troy-ounces  of  iodide  of 
potassium,  combining  in  equivalent  proportion  with  sulphate  of  am- 
monia— supposing  the  latter  to  contain  no  water  of  crystallization — 
require  more  than  one  troy-ounce  of  the  latter,  as  the  following  dia- 
gram shows : 
KI  (166)  +  NH40,S03(66)  =  KO,S03(87)  +  NH4I  (145),  hence 
1920  grs.  of  iodide  of  potassium  require  for  complete  decomposition 
'764  grs.  of  sulphate  of  ammonia.  Now,  since  it  is  safer  to  employ 
an  excess  of  sulphate  of  ammonia  than  of  iodide  of  potassium,  the 
quantity  of  the  former  should  not  be  less  than  867  grains,  which 
would  make  allowance  for  an  additional  equivalent  of  water  in  the 
sulphate,  and  any  excess  of  the  latter  would  be  thrown  down  along 
with  sulphate  of  potassa  by  alcohol. 
As  regards  the  process  for  preparing  bromide  of  ammonium,  I  al- 
most regret  that  the  Committee  did  not  adopt  the  same  plan  here  as 
in  the  case  of  the  iodide.  It  is  true  that  the  product  will  not  con- 
tain any  foreign  salt,  such  as  sulphate,  and  that  the  only  drawback 
in  this  process  is  the  not  unfrequent  elimination  of  bromine  and  hy- 
-drobromic  acid ;  but  I  am  inclined  to  think  the  advantage  is  on  the 
side  of  the  other  process,  which  yields  a  product,  never  exhibiting 
•any  signs  of  decomposition,  although  containing  a  very  small  amount 
of  sulphate  of  potassa,  and  being  all  that  can  be  desired  by  the  pho- 
tographer as  well  as  by  the  pharmacist.    I  have  prepared  several 
