PREPARATION  OF  ARTIFICIAL  COLORINa  MATTERS,  ETC.  245 
There  are  thus,  I  think,  several  advantages  which  attend  the 
preparation  of  Liquor  Potassse  by  the  process  I  have  described. 
This  process  is  more  easily  performed  than  any  of  those  con- 
tained in  our  Pharmacopoeias,  and  it  is  less  likely  to  yield  pro- 
ducts of  variable  strength  and  quality.  There  is  one  point, 
however,  to  which  attention  must  be  particularly  paid,  and  that 
is  the  condition  of  the  carbonate  of  potash.  I  have  assumed 
that  the  so-called  salt  of  tartar  of  commerce,  which  the  London 
College  orders,  is  to  be  used  in  the  process.  This,  according  to 
the  Pharmacopoeia,  is  a  sesquihydrated  carbonate,  containing 
sixteen  per  cent,  of  water;  but  as  it  rapidly  absorbs  more  water 
on  exposure  to  the  air,  it  cannot  be  relied  on  as  a  definite  com- 
pound in  the  state  in  which  it  is  met  with  in  commerce.  Unless 
it  be  perfectly  dry,  and  does  not  in  the  least  adhere  to  the  bot- 
tle containing  it,  it  should  not  be  used  without  being  previously 
heated  with  constant  agitation  in  a  porcelain  dish  placed  over  a 
water-bath.  It  is  readily  tested  with  regard  to  the  water  it 
contains  by  the  means  indicated  in  the  Pharmacopoeia.  One 
hundred  grains  of  it,  on  being  heated  to  redness,  should  lose 
sixteen  grains. 
The  proposed  formula  for  Liquor  Potassae  is  so  constructed 
that,  if  troy  weight  be  used,  the  solution  will  be  identical  in 
strength  with  that  now  ordered  in  the  London  Pharmacopoeia, 
but  if  the  avoirdupois  ounce  be  substituted  for  the  troy  ounce, 
the  strength  of  the  solution  will  be  slightly  reduced,  so  that 
one  hundred  grain-measures  of  it  will  contain  five  grains  of 
anhydrous  potash  (KO),  and  the  specific  gravity  of  this  solu- 
tion will  be  1-053. — London  Pharm.  Jour.^  March,  186L 
ON  THE  PREPARATION  OF  ARTIFICIAL  COLORING  MATTERS 
WITH  THE  PRODUCTS  EXTRACTED  FROM  COAL  TAR. 
By  M.  E.  Kopp. 
(Continufd  fiom  page  136.) 
3.  Reduction  of  Nitrohenzole  hy  Ferrous  Acetate, — Ferrous 
acetate  reacts  on  nitrohenzole  and  converts  it  into  aniline,  while 
the  sulphate,  chloride,  and  oxalate  of  iron  have  no  action  on  it. 
The  reaction  is  represented  by  the  formula — 
