208  Effervescing  Preparations.  {Am£y%87h6arm' 
present,  than  the  magnesia  solution.  It  is  a  permanent  solution,  and 
does  not  precipitate  nor  became  cloudy,  after  a  few  days,  as  the  mag- 
nesia solution  frequently  does.  It  is  as  palatable  and  pharmaceutically 
elegant  as  the  magnesia  solution,  superior  to  it  in  medicinal  value, 
and  of  much  more  profit  to  the  pharmacist  in  manufacturing. 
The  formula  which  I  have  ascertained  to  give  the  most  stable  pro- 
duct and  gratifying  results  is  the  following,  viz  : 
Take  of  sodium  carbonate,         .  .  .  £1 
acid  tartaric,  in  crystals,        .  .  .  £vi 
oil  of  lemon,  .  .  .  gtt.  iii 
simple  syrup,  ....  f^iss 
pure  water,    .  .  .  q.  s.  ft.  f^xii 
The  operation  is  as  follows  :  reduce  the  sodium  carbonate  to  pow- 
der, rub  the  oil  of  lemon  intimately  with  it,  and  then  add  water 
sufficient  to  dissolve  ;  to  this  solution  add  five  drachms  of  the  tartaric 
acid,  and  stir  occasionally  till  the  acid  is  dissolved.  Filter  this  solution 
to  remove  any  impurities  which  may  be  present,  or  any  cloudiness 
resulting  from  the  introduction  of  the  oil  of  lemon.  To  this  filtrate 
add  the  syrup,  agitate  thoroughly,  then  add  one  drachm  of  tartaric 
acid  (the  remaining  amount),  cork  and  tie  immediately  to  preserve  the 
carbonic  acid  gas  ;  finally,  agitate  the  contents  of  the  bottle  occasionally 
till  the  acid  is  all  dissolved,  and  keep  in  a  cool  place  cork  downwards. 
The  reasons  for  using  the  acid  in  crystals  for  producing  the  tartrate, 
are  these  :  The  commercial  powdered  acid  usually  contains  impuri- 
ties, and  sometimes  adulterations,  not  present  in  the  crystals  ;  to  powder 
them  previously  to  adding  to  the  alkaline  solution  would  be  an  unnec- 
essary occupation  ;  finally  the  reaction  is  performed  much  slower  and 
more  regularly  than  where  the  powdered  acid  is  used,  an  object,  I 
think,  greatly  to  be  desired  in  processes  evolving  much  carbonic  acid 
gas.  The  last  portion  of  the  acid  could  be  added  by  dissolving  it  first 
in  the  syrup  and  adding  this  solution,  but  in  doing  this  the  reaction  is 
severe  and  instantaneous,  so  that  much  gas  is  often  lost,  while  with 
the  crystals  the  reaction  is  moderate,  and  sufficient  time  is  given  for 
inserting  the  cork,  and  for  the  gas  to  dissolve  in  the  liquid. 
Prepared  in  this  manner,  effervescing  solution  of  sodium  tartrate  is 
a  very  agreeable  beverage,  and  can  be  preserved  unimpaired  for  most 
any  length  of  time,  samples  having  been  kept  through  the  hot  months 
uninjured. 
I  have  found  such  a  wide  difference  in  samples  of  sodium  carbonate, 
