Aw'ocuimaTm'}      Titration  of  Ammonium  Carbonate.  501 
tion  would  neutralize  2*616  grms.  ammonium  carbonate,  and  the 
pharmacopoeial  requirement  is  correct  for  the  officinal  salt. 
The  National  Dispensatory  (page  177)  states  the  salt  formerly  in 
the  market  was  represented  by  the  formula  2NH4HC03.NH4NH2C02 
molecular  weight=236. 
The  reaction  of  such  a  salt  with  oxalic  acid  would  be  represented 
by  the  equation — 
2NH4HC03.NH4NH2C02+H20+2H2C204,2HO-:2(NH4)CA+3 
C02-f  5H20, 
236  grm.  neuralizing  252  grm.  of  oxalic  acid.  Consequently  3*15 
grm.  oxalic  acid,  the  amount  contained  in  50  cc.  of  normal  solution, 
would  neutralize  2-95  grm.  of  a  salt  of  this  composition. 
Much  of  the  commercial  carbonate  of  ammonium  does  not  answer 
the  requirements  of  the  Pharmacopoeia.  Dr.  Divers  (loc.  cit.,  page 
240)  states  that  he  had  found  one  exception  to  the  uniformity  of  the 
commercial  carbonate.  This  on  analyzing  gave  numbers  nearly  iden- 
tical with  those  of  the  acid  carbonate.  Prof.  Bridges  (Amer.  Jour. 
Phar.,  1874,  page  540)  likewise  called  attention  to  this  salt  existing 
in  a  commercial  carbonate.  More  recently,  Kraut  [Archiv  d.  Pharm., 
1885,  page  21)  noticed  the  same.  My  own  experience  leads  me  to 
believe  that  considerable  of  this  acid  carbonate  has  been  put  on  the 
market  by  an  American  manufacturer ;  perhaps  unintentionally,  from 
a  desire  to  make  a  solid  carbonate  which  would  keep  well.  Four 
samples  recently  examined  gave  the  following  results,  two  determina- 
tions being  made : 
Quantity  taken.  Normal  Oxalic  Acid  required. 
No.  1,  American   2  616  grni.  35-3  cc.  34'6  cc. 
No.  2,  American   2  616  grm.  41*4  cc.  41*0  cc. 
No.  3,  American  (Squibb's).  2  616  grm.  50'0  cc.  49  5  cc 
No.  4,  English   2  616  grm.  49 '0  cc.  487  cc. 
Sample  No.  1  was  a  very  hard,  clear  salt,  with  but  a  faint  odor  of 
ammonia,  and  on  exposiug  a  piece  to  the  air  for  several  days  the 
odor  of  ammonia  was  lost,  the  salt  remaining  nearly  as  translucent  as 
before  exposure.  From  its  saturating  equivalent,  2*616  grm.  neutral- 
izing 34*6  cc.  normal  oxalic  solution,  I  believe  it  to  have  been  nearly 
pure  acid  carbonate  (2*616  grm.  acid  carbonate  requires  33*11  normal 
oxalic  acid  solution.)  Samples  No.  1  and  No.  2  were  not  free  from 
empyremnatic  substances,  No.  1  having  particularly  a  strong  urine-like 
odor. 
