AmiiJSa906ym'}       The  U.S.P.  Inorganic  Chemicals.  391 
that  it  makes  a  very  soluble  salt,  and  impurities  associated  with 
the  sulfate  of  aluminum  and  sulfate  of  sodium  used,  are  not 
removed  by  crystallization  from  the  alum.  Again,  in  my  experience, 
soda  alum  cannot  be  crystallized  except  from  strong  solution  of 
sulfate  of  aluminum,  in  which  it  is  slightly  soluble,  and  even  when 
obtained,  it  effloresces  so  that  it  loses  water  of  crystallization,  under 
ordinary  circumstances,  destroying  the  crystalline  appearance  of  the 
salt  and  rendering  it  not  constant  in  strength." 
Aliimmi  Sulphas. — The  U.S.P.  stands  almost  alone  in  recognizing 
3.  salt  with  16  molecules  of  water  of  crystallization,  while  all  other 
pharmacopoeias  require  a  salt  with  18  molecules.  Examination  of 
American- made  samples  showed  that  the  percentage  of  water  varies 
from  45-49  to  45  6  per  cent.,  while  a  sample  of  Merck's  contained 
4492  per  cent,  of  water;  16  molecules  of  water  of  crystallization 
represent  45-7  per  cent,  of  water,  15  molecules  represent  44- 10  per 
cent,  of  water,  hence  we  are  justified  in  retaining  the  old  text. 
Ammonium  Benzoate. — The  solubility  of  this  salt  varies  according 
as  to  whether  it  is  of  neutral  or  acid  reaction ;  the  latter  condition 
is  more  usually  met  with  because  of  the  readiness  with  which  the 
salt  loses  in  ammonia  gas  on  standing. 
Ammonium  Carbonate. — The  composition  of  this  unaltered  salt  is 
represented  by  equal  molecular  quantities  of  acid  carbonate  and 
carbamate  which  yield  theoretically  32-55  per  cent,  of  ammonia  gas. 
The  British  Pharmacopoeia  limits  the  ammonia  strength  of  this  salt 
to  31-66  per  cent.  Various  samples  of  the  unaltered  translucent 
salt  confirm  this  accepted  formula.  A  salt  which  consists  of  two 
molecules  of  the  bicarbonate  to  one  of  the  carbamate,  yields  only 
22  88  per  cent,  of  ammonia.  The  U.S.P.  '90  standard  was  100  per  cent., 
which  is  difficult  to  comply  with.  With  the  improvements  made 
recently,  the  standard  of  97  per  cent,  is  not  difficult  to  maintain. 
Ammonium  Salicylate. — This  salt  is  furnished  either  as  a  crystal- 
line anhydrous  salt  or  crystallized  with  one-half  molecule  of  water. 
Merck's  salt,  which  is  in  colorless  well-defined  crystals,  is  anhydrous, 
and  has  evidently  been  crystallized  from  alcohol.  Others  of  American 
origin  are  either  in  large  irregular  crystals  with  one-half  molecule  of 
water,  or  an  anhydrous  fine  crystalline  powder.  Ammonium  salicylate 
is  quite  as  stable  as  the  other  inorganic  ammonium  salts.  At  100°  C, 
it  commences  to  slowly  volatilize,  and  at  this  temperature  does  not 
lose  over  075  per  cent,  of  ammonia.  The  percentage  of  ammonia 
yielded  by  the  samples  examined  : — 
