ON  EFFERVESCING  POWDERS. 
49 
ON   EFFERVESCING  POWDERS. 
By  Jno.  M.  Maisch,  of  Philadelphia. 
Effervescing  powders  are  used  on  account  of  the  carbonic  acid 
in  gaseous  state  which  is  generated  as  soon  as  they  are  thrown 
into  water  to  dissolve.  The  carbonic  acid  is  highly  esteemed 
for  its  agreeable  refrigerance,  or  it  is  employed  to  mask  to  a 
certain  extent  the  taste  of  other  medicines.  The  generation  of 
carbonic  acid  is  effected  by  the  mutual  decomposition  of  a  car- 
bonate with  a  vegetable  acid  or  an  acid  salt.  Of  the  carbonates 
used,  the  preference  is  usually  given  to  the  bicarbonate  of  po- 
tassa  or  soda,  seldom  only  the  officinal  carbonate  of  magnesia  or 
monocarbonate  of  soda  are  employed  ;  carbonate  of  potassa  is 
entirely  unfit  to  enter  into  such  a  combination,  owing  to  its 
deliquescence. 
Among  the  acids,  recourse  is  had  to  the  tartaric  and  citric, 
they  being  the  only  two  officinal  acids  suitable  for  such  a  prepa- 
ration ;  sometimes  they  are  replaced  by  bitartrate  of  potassa, 
the  object  of  which  is  to  have  the  evolution  of  carbonic  acid 
going  on  in  the  stomach. 
In  the  United  States  and  England,  the  carbonate  and  the 
acid  are  usually  kept  in  two  separate  papers,  distinguished  by 
their  blue  and  white  color,  while  on  the  continent  of  Europe,  for 
its  greater  convenience,  a  mixture  of  the  two  is  habitually  em- 
ployed and  is  even  officinal  in  most  of  the  continental  Pharma- 
copoeias. 
The  U.  S.  Pharmacopoeia  has  no  officinal  formula  for  any  of 
these  powders ;  however  it  is  customary  for  the  apothecary  to 
prepare  two  different  kinds,  one  under  the  name  of  "  soda  pow- 
ders' which  shall  contain  for  one  dose  30  grains  of  bicarbonate 
of  soda  in  a  blue  paper,  and  25  grains  of  tartaric  acid  in  a  white 
one.  The  «  Seidlitz  powders,"  intended  for  a  slight  laxative, 
require  2  drachms  of  tartrate  of  soda  and  potassa  with  10  grains 
of  bicarbonate  of  soda  in  a  blue,  and  30  grains  of  tartaric  acid 
in  a  white  paper.  These  powders  became  officinal  in  the  Prussian 
Pharmacopoeia  under  the  name  of  English  effervescing  powders, 
(Pulvis  aerophorus  Anglicus)  and  are  put  up  in  the  greatest  part 
of  Europe  in  accordance  with  this  formula.  It  has  been  propo- 
sed by  Dr.  Mohr  to  substitute  tartrate  of  soda  for  Rochelle  salt, 
4 
