266    ON  THE  PREPARATION  OF  PURE  CARBONATE  OF  POTASH. 
ON  THE  PREPARATION  OF  PURE  CARBONATE  OF  POTASH. 
By  M.  Bloch. 
With  the  view  of  avoiding  the  trouble  of  purifying  the  cream 
of  tartar  and  the  destruction  of  an  equivalent  of  tartaric  acid  in 
the  preparation  of  pure  carbonate  of  potash,  the  author  has  em- 
ployed the  following  method. 
The  bitartrate  of  potash  is  boiled  with  its  equivalent  of  car- 
bonate of  lime.  The  liquid  is  filtered,  and  a  few  drops  of  nitric 
acid  are  added  to  it ;  the  contained  chloride  is  then  precipitated 
by  a  few  drops  of  nitrate  of  silver.  The  liquid  is  then  passed 
through  a  filter  moistened  with  water  acidulated  with  pure  nitric 
acid,  evaporated  to  dryness  in  an  iron  pot,  and  the  residue  ex- 
posed to  a  red  heat.  A  little  water  is  sprinkled  on  the  red-hot 
mass,  in  order  to  decompose  the  cyanide  which  has  been  formed. 
It  is  advisable  to  keep  the  materials  constantly  stirred,  in  order 
to  equalize  the  reactions  and  obtain  a  homogeneous  mass.  The 
whole  is  then  treated  with  pure  water,  filtered,  and  evaporated  to 
dryness. 
The  carbonate  thus  prepared  is  perfectly  pure,  and  contains  no 
trace  of  chloride,  a  body  which  it  was  exceedingly  difficult  to  get 
rid  of  by  the  old  methods.  The  other  advantage  attending  it  is, 
that  an  equivalent  of  tartaric  acid  is  obtained  from  every  equiva- 
lent of  bitartrate  of  potash  employed,  being  thrown  down  in  the 
first  instance  in  the  form  of  insoluble  tartrate  of  lime. — London 
Chemical  Gazette,  fiom  Comptes  llendus,  Feb,  12.  1855,  p.  364. 
ON  THE  ACTIVE  PRINCIPLE  OF  CENTAUREA  CALCITRAPA. 
By  L.  Colignon. 
Centaurea  calcitrapa  exhibits  a  powerful  febrifuge  action.  The 
author  has  endeavored  to  prepare  its  active  principle.  This 
however  is  not  an  alkaloid,  and  cannot  be  obtained  in  a  crystalline 
form.  It  has  an  intense  and  styptic  bitter  taste,  has  a  trans- 
parent amber  color,  and  a  syrupy  consistence  ;  it  is  not  volatile, 
is  decomposable  by  heat,  strongly  reddens  litmus-paper,  dissolves 
readily  in  alcohol  and  ether,  but  is  only  sparingly  soluble  even 
in  boiling  water  ;  with  potash,  soda,  and  ammonia  it  forms  soluble 
but  uncrystallizable  salts,  and  with  lime  and  oxide  of  lead 
insoluble  salts. 
