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ACTION  OF  CARBONIC  AND  BORACIC  ACIDS. 
answer  any  purpose  better  than  aloes,  and  should  be  administered, 
because  it  can  be  obtained  at  a  moderate  price,  twelve  pounds  of 
fresh  expressed  juice  yielding  about  eight  ounces  of  cathartin. — 
New  York  Journal  of  Pharmacy,  April,  1853,  from  Jul.  Iiu- 
thardt,  Pharmaceut. 
THE  ACTION  OF  CARBONIC  AND  BORACIC  ACIDS  ON 
TINCTURE  OF  LITMUS. 
Malaguti  observes,  that  these  acids  behave  towards  tincture  of 
litmus  as  all  other  acids,  when  they  are  allowed  to  act  in  suffi- 
cient quantity.  These  acids,  as  is  known,  communicate  a  wine 
coloration  to  the  tincture  ;  they  are  considered,  on  that  account, 
as  very  weak  acids,  because  the  other  acids  only  produce  this 
coloration  when  they  are  diluted  in  an  extraordinary  degree. 
When  carbonic  is  forced,  under  a  pressure  of  lj  to  2  atmos- 
pheres, into  diluted  tincture  of  litmus,  it  colors  the  tincture 
onion-red ;  but  when  the  pressure  is  removed,  and  the  excess  of 
gas  separated,  either  by  a  vacuum  or  a  gentle  heat,  the  tincture 
acquires  a  wine-red  color.  When  a  little  tincture  of  litmus  is 
poured  into  a  hot  saturated  solution  of  boracic  acid,  after  it  has 
cooled  for  twenty-four  hours,  and  the  excess  of  acid  separated, 
the  mixture  assumes  a  wine-red  color ;  however,  when  the  mix- 
ture is  heated  to  dissolve  the  excess  of  boracic  acid,  it  becomes 
onion-red.  When  the  excess  of  acid  is  allowed  to  crystalline 
out,  it  assumes  again  the  wine-red  color.  When  the  fluid  is 
viewed  in  a  thick  stratum,  in  a  glass  tube,  in  the  direction  of  its 
axis,  the  difference  of  the  shades  of  color  between  a  hot  satu- 
rated and  a  cold  saturated  solution  may  be  easily  perceived. 
A  hot  saturated  solution  of  boracic  acid  produces  an  onion-red 
color,  when  a  little  tincture  of  litmus  is  poured  into  it. 
Sulphuretted  hydrogen  gas  cannot  be  applied  for  a  similar 
experiment,  because  it  acts  as  a  reducing  agent  on  the  coloring 
matter  when  pressed  into  the  tincture  of  litmus. — Annals  of 
Pharmacy,  July,  1853. 
