ON  EFFERVESCING  POWDERS. 
55 
for  some  time  according  to  the  plan  suggested  by  Professor 
Otto.  As  citric  acid  contains  much  water  of  crystallization 
(4  equiv.)  it  might  probably  in  this  case  be  advisable  to  first 
expel  the  same  by  exposure  to  heat,  and  after  it  has  become 
quite  cool  to  mix  it  with  the  other  ingredients  previously  finely 
powdered.  It  might  be  of  great  service  upon  voyages  in  cases 
where  saving  of  space  is  of  some  account,  and  where  bottles 
cannot  be  well  packed  ;  it  would  combine  smallness  of  bulk  and 
portability,  and  for  these  reasons  would  be  preferable  to  the  offi- 
cinal solution.  Its  great  advantage  over  the  soluble  citrate  of 
magnesia  would  be  its  cheapness  and  its  far  more  refreshing 
taste,  produced  by  the  carbonic  acid  set  free  and  the  citric  acid 
still  in  solution.  The  citric  acid  in  the  formula  given  may  be 
augmented,  but  as  the  reaction  does  not  take  place  at  once,  and 
as  it  is  drank  before  the  saturation  is  completed,  there  is  no 
reason  for  doing  so ;  the  solution  will  still  hold  a  sufficiency  of 
free  citric  acid  to  cover  the  taste  of  the  magnesia  salt,  and 
render  the  draught  quite  a  refreshing  one  ;  the  chemical  reaction 
is  completed  in  the  stomach. 
If  the  administration  of  an  iron  salt  is  intended,  Colombat's 
formula  given  above  may  be  used,  and  all  the  ingredients  mixed 
into  one  powder ;  but  it  must  be  carried  in  mind  that  this  re- 
sults in  a  tartrate  of  the  protoxide  of  iron.  As  it  has  always 
been  a  desideratum  how  to  administer  a  carbonate  of  the  prot- 
oxide of  iron  in  an  unaltered  state,  and  as  even  Vallet's  mass 
becomes  oxidized,  the  following  mode  of  administration  is  sug- 
gested. Sulphate  of  iron  5iss,  tartaric  acid  Bijss,  dry  carbon- 
ate of  soda  Biijss,  sugar  3iij.  The  chalybeate  waters  contain 
usually  the  carbonate  of  protoxide  of  iron,  dissolved  by  an  excess 
of  carbonic  acid,  besides  some  alkaline  salts.  Physicians  value 
these  waters,  because  they  are  usually  better  adapted  to  the  di- 
gestive organs  and  are  easier  assimilated,  consequently  of  a 
quicker  and  more  reliable  action  on  the  human  frame  than  the 
ordinary  ferruginous  preparations.  These  properties  are  doubt- 
less due  to  the  presence  of  that  mild  acid,  the  carbonic  and 
probably  to  the  aperient  salts,  both  of  which  combine  their  ac- 
tion with  that  of  the  iron.  In  the  formula  given  above  sufficient 
carbonic  acid  is  generated  to  convert  the  iron  salt  into  a  carbonate 
of  the  protoxide,  and  keep  the  same  in  solution.    Thrown  into 
