20 
PREPARATION  OF  PYROGALLIC  ACID,  ETC. 
Twenty-eight  kilogrammes  (61J  lbs.)  of  sulphuric  acid,  at 
66°  B.  are  diluted  with  5600  kilogrammes  (12337  lbs.)  of  water, 
and  heated  to  212°  F.  On  the  other  hand,  a  similar  quantity 
of  liquid,  at  86°  F.,  is  mixed  with  2240  kilogrammes  (4935  fibs.) 
of  starch  and  heated  to  100°  F.,  agitated  constantly,  and  intro- 
duced little  by  little  into  the  open  boiler,  heated  by  steam  till  it 
is  at  212°  F.,  when  the  boiler  is  closed  and  heated  to  320°  F., 
and  maintained  at  this  temperature  during  some  time.  In  from 
two  to  four  hours  the  presence  of  starch  is  not  detected  by  tests, 
when  the  solution  is  drawn  off  into  a  wooden  vessel  and  incor- 
porated with  168  kilogrammes  (372  lbs.)  of  carbonate  of  lime 
suspended  in  500  kilogrammes  (1101J  lbs.)  of  water,  allowed 
to  deposite  till  clear,  drawn  off,  and  evaporated  to  20°  B., 
clarified  with  blood  and  charcoal,  etc.,  in  the  ordinary  manner. 
— Journ.  de  Pharm.,  from  Mechan.  Mag.  w.  p. 
ON  THE  PREPARATION  OF  PYRO-GALLIO  ACID  AND 
SOME  OF  ITS  PROPERTIES. 
By  MM.  de  Luynes  and  Espandieu. 
Pyrogallic  acid,  first  studied  by  Berzelius  and  Braconnot,  was 
the  object  of  remarkable  researches  by  Pelouze  in  1834,  who, 
in  describing  its  chief  properties,  made  known  the  laws  which 
govern  its  formation.  Thanks  to  Chevereul,  Begnault,  and 
Liebig,  pyrogallic  acid  has  received  numerous  and  useful  appli- 
cations. Its  employment  in  the  analysis  of  air,  in  photogra- 
phy, and  in  dying  the  hair,  give  it  an  important  place  among 
chemical  products. 
The  properties  and  constitution  of  pyrogallic  acid  are  worthy 
of  the  interest  of  the  theorist.  We  have  undertaken  these  re- 
searches to  discover  its  true  chemical  nature.  Although  our 
work  is  not  completed,  we  believe  that  these  first  results  are 
worthy  of  presentation  to  the  Academy. 
The  first  point  which  has  attracted  our  attention  is  the  pre- 
paration of  pyrogallic  acid.  According  to  M.  Pelouze,  gallic 
acid,  heated  in  a  bath  to  410°  F.  in  a  retort,  is  completely  sepa- 
rated into  carbonic  acid  and  pyrogallic  acid. 
*      CuH6O10  =  2C02  +  C12H606, 
