ON  EFFERVESCING  POWDERS. 
57 
powder  and  solution  hardly  requiring  more  than  a  little  sweeten- 
ing to  render  it  pleasant  to  take.  If  the  full  effects  of  ammonia 
are  quickly  desired,  we  have  no  other  preparation  for  such  a  pur- 
pose, but  the  various  preparations  of  caustic  ammonia  and  the 
officinal  sesquicarbonate.  This  latter  one  only  can  be  made  into 
pills,  but  is  usually  given  in  solution,  like  spiritus  and  aqua  am- 
monice  ;  their  taste  and  smell,  however,  are  so  very  pungent  and 
penetrating  that  they  cannot  be  covered  or  masked,  either  by 
aromatics  or  mucilages.  As  they  are  valuable  remedies  in  scarlet 
fever,  the  small  children,  for  whom  they  are  prescribed,  often 
object  to  taking  them.  We  have,  I  believe,  a  much  more  con- 
venient and  pleasant  form  to  secure  the  effects  of  ammonia  with- 
out incurring  its  penetrativeness  ;  we  may  arrive  at  this  end  in  a 
somewhat  similar  way  as  above,  in  trying  to  obtain  the  proper- 
ties of  carbonate  of  protoxide  of  iron.  If  a  solution  of  the  neu- 
tral tartrate  of  ammonia  is  mixed  with  a  solution  of  carbonate 
of  potassa,  an  ammoniacal  smell  will  soon  be  perceived,  and  a 
glass  rod,  moistened  with  muriatic  acid,  will  evolve  thick  white 
vapors  if  held  above  the  surface  of  the  liquid.  An  interchange 
has  taken  place,  a  double  decomposition,  by  which  tartrate  of 
potassa  and  carbonate  of  ammonia,  has  been  formed. 
If  bitartrate  of  ammonia  is  mixed  with  a  solution  of  carbonate 
of  potassa,  an  effervescence  will  take  place,  and  the  formation 
of  a  double  tartrate  of  the  two  bases  ;  a  further  addition  of  carbo- 
nate of  potassa  will  displace  the  ammonia  from  its  combination, 
which,  with  the  carbonic  acid  of  the  potassa  salt  and  that  still 
held  back  by  the  solution,  combines  to  bicarbonate  or  sesqui- 
carbonate of  ammonia.  But  if,  after  the  saturation  of  the  bitar- 
trate of  ammonia  with  carbonate  of  potassa,  the  carbonic  acid  is 
expelled  by  a  moderate  heat,  or  if  the  double  tartrate  of  potassa 
and  ammonia  be  taken  at  once,  the  subsequent  addition  of  carbo- 
nate of  potassa  causes  the  formation  of  monocarbonate  of  am- 
monia. Bicarbonate  of  potassa  usedin  place  of  the  carbonate,  will, 
in  all  cases,  cause  the  same  result,  that  is,  the  production  of  bi- 
carbonate of  ammonia.  Consequently,  if  we  want  the  formation 
of  monocarbonate  of  ammonia,  we  have  to  bring  in  contact 
neutral  tartrate  of  ammonia,  or  its  double  salt  with  tartrate  of 
potassa,  and  carbonate  of  potassa  ;  as  this  latter,  however,  can- 
not be  dispensed  in  form  of  powder,  and  as  it  dissolves  in  water 
