i88 
Note  on  Soda  Mint. 
Am.  Jour.  Pharm. 
April,  1892. 
preparation  extemporaneously,  which  is  frequently  the  case.  If  the 
menthol  is  dissolved  in  the  aromatic  spirit  of  ammonia,  and  the 
water  containing  the  soda  is  added  to  the  solution,  separation 
immediately  takes  place.  A  small  portion  remains,  however,  in 
solution,  and  the  agreeable,  cooling  menthol  taste  is  present. 
Considerable  difference  exists  in  the  various  formulas  regarding 
the  amount  of  aromatic  spirit  of  ammonia  in  the  preparation. 
Some  omit  it  altogether,  while  others  order  as  much  as  one  ounce  to 
the  pint.  The  National  Formulary  directs  60  minims  to  this 
amount,  which,  compared  to  other  formulas,  is  rather  weak.  Manu- 
facturers of  soda  mint  tablets,  in  the  ammonia  strength  as  well  as 
in  the  oil  selection,  follow  the  old  method.  Usually  each  tablet 
contains,  or  is  stated  to  contain,  4  grains  bicarbonate  of  sodium,  j£ 
grain  carbonate  of  ammonium,  with  yfc  drop  of  oil  of  peppermint. 
Calculating  on  this  basis,  80  such  tablets  will  furnish  the  amount  of 
soda  in  one  pint  of  N.  F.  soda  mint.  The  amount  of  carbonate  of 
ammonia  (20  grs.)  is,  however,  the  one  present  in  one  fluidounce 
U.  S.  P.  aromatic  spirit  of  ammonia,  omitting  the  free  water  of 
ammonia  altogether.  The  National  Formulary  may,  perhaps,  be 
improved  upon  by  increasing  the  amount  of  aromatic  spirit  of 
ammonia  to  about  T/2  ounce. 
In  connection  with  this  subject  a  few  words  on  the  popular  soda 
mint  tablets  may  be  in  order.  The  presence  of  carbonate  of  ammo- 
nium has  a  tendency  to  decompose  or  alter  the  physical  condition 
of  the  tablets.  They  become  softer  and  very  friable,  and  some- 
times assume  a  brown  color.  Free  ammonia  is  developed  through 
the  action  of  the  sodium  salt  on  the  ammonium  carbonate.  This 
may  be  observed  if  a  bottle,  containing  a  number,  is  opened,  when 
the  ammonia  can  be  detected  by  its  powerful  odor  or  a  little  HC1 
on  a  glass  rod.  By  prolonged  exposure  to  air,  the  ammonia  almost 
entirely  disappears. 
The  brown  color  mentioned  is  probably  due  to  the  action  of  the 
alkalies  upon  the  oil  present.  To  determine  if  such  was  the  case, 
a  mixture  of  commercial  oil  of  peppermint,  with  a  5  per  cent, 
aqueous  potash  solution  was  made,  repeatedly  agitated  and  allowed 
to  stand.  It  separated  into  two  layers,  and  after  several  days  the 
potassa  layer  assumed  a  brown  color.  An  alcoholic  solution  of 
menthol,  made  to  undergo  the  same  treatment,  is  apparently  not 
influenced  in  this  manner.    Perhaps  this  latter  fact  may  be  utilized 
