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ON  COBALTIC  ACID. 
de  Luynes  has  adopted  the  following  process  : — He  mixed  orcine 
with  twenty-five  times  it  weight  of  crystallized  carbonate  of  soda, 
and  five  times  its  weight  of  water,  with  the  addition  of  a  weight 
of  liquid  ammonia,  not  more  than  equal  that  of  the  orcine,  in 
imperfectly  stopped  mattrasses.  He  heated  the  whole  to  between 
60°  and  80°  for  four  or  five  hours,  taking  care  to  stir  it  from 
time  to  time.  The  dark  violet-blue  liquid  he  diluted  with  water 
and  saturated  with  a  slight  excess  of  hydrochloric  acid,  which 
precipitated  the  coloring  matter  ;  this  latter  washed  and  dried  is 
pure  litmus. 
Litmus  thus  prepared  is  in  the  form  of  small  irregular  masses 
with  the  variegated  metallic  reflections  common  to  most  coloring 
matters.  It  is  very  slightly  soluble  in  cold  water,  to  which  it 
imparts  a  wine-colored  tinge,  which  by  contact  with  acid  turns 
to  the  color  of  onion  skin,  and  with  alkalies  to  violet  blue.  In 
alcohol,  also,  which  it  colors  yellow.  Concentrated  sulphuric 
acid  dissolves  it,  taking  a  very  rich  violet-blue  color,  which  be- 
comes light  red  on  the  addition  of  a  large  quantity  of  water. 
The  alcoholic  solution,  diluted  with  water,  constitutes  a  reagent 
extremely  sensitive  to  the  slightest  trace  of  alkaline  substance. 
By  adding  a  little  potash  to  it,  a  blue  liquid  is  obtained,  which, 
in  contact  with  acids,  sulphuretted  hydrogen,  and  other  com- 
pounds, behaves  in  the  same  way  as  ordinary  litmus  solution. 
Dry  litmus,  heated  in  tube,  gives  an  abundant  deposit  of  car- 
bon, and  disengages  ammonia. 
The  preparation  of  ordinary  litmus  solution  requires  some 
time ;  it  does  not  keep  long  without  altering,  and  to  render  it 
sensitive  the  excess  of  alkali  it  contains  must  be  saturated.  M. 
de  Luynes'  product  keeps  without  altering  in  the  dry  state  :  the 
cold  solution  can  be  very  rapidly  prepared,  and  may  be  immedi- 
ately employed  in  any  determinations  by  standard  solutions. — 
Lond.  Chem.  News,  March  31,  J  865. 
ON  COBALTIC  ACID. 
The  existence  of  cobaltic  acid,  which  has  long  been  suspected, 
seems  to  be  proved  by  M.  Winkler's  experiment.  According  to 
him,  by  boiling  different  cobalt  products,  but  more  especially  the 
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