Aji.  Jotjr.  Pharm.  \ 
Sept.  1,  1872.  J 
Our  Writing  Fluids. 
415 
Let  us  now  glance  at  the  properties  of  the  various  ingredients  used 
in  the  process.  If  we  use  an  excess  of  galls  we  simply  throw  away 
money,  and  render  the  ink  more  liable  to  mould.  If  we  use  an  excess 
of  iron,  the  galls  being  insufficient  to  decompose  it,  the  characteristic 
color  of  its  oxide  is  soon  shown  by  the  writing  becoming  brown.  The 
use  of  an  excess  of  gum  causes  the  ink  to  clog  the  pens,  and  the  writ- 
ing to  be  wanting  in  fluency.  About  twenty-five  years  ago  an  ink 
named  Japan  ink  was  very  much  in  use  ;  it  produced  a  beautiful  glossy 
appearance  when  written,  but  clogged  the  pen  so  much  that  it  soon 
fell  into  disuse ;  its  defect  was  too  much  gum.  The  water  should  be 
as  soft  as  possible — that  is,  it  should  contain  no  lime,  or  other  earthy 
matter;  hence  rain  water,  or,  better,  distilled  water,  is  frequently 
prescribed  in  receipts  for  making  ink.  The  cheapest  ink  which  has 
hitherto  been  introduced,  is  one  composed  of  a  saturated  solution  of 
logwood,  obtained  by  boiling  twenty-two  pounds  of  logwood  in  a  suf- 
ficiency of  water  to  produce,  after  being  strained,  fourteen  gallons  of 
liquor ;  to  this  decoction  one  pound  (avoirdupois)  of  yellow  chromate 
of  potash  (not  bichromate)  is  added  in  solution  ;  the  proportions  are 
one  thousand  parts  of  solution  to  one  of  chromate ;  the  change  of 
color  is  not  an  immediate  one,  but  gradually  becomes  darker.  The 
experiment  may  be  tried,  on  the  small  scale,  by  using  logwood  a  quar- 
ter of  a  pound  boiled  in  water  to  produce  two  pints,  to  which,  when 
strained,  add  twenty  grains  of  chromate  of  potash  in  solution. 
We  will  now  glance  at  the  composition  of  u  writing-fluids  "  used 
for  special  purposes ;  thus  we  know  that  writing  which  is  intended  to 
be  copied  is  written  with  ink  containing  either  gum,  sugar,  treacle, 
glycerin,  or  some  such  substance,  which  causes  the  writing  to  retain 
moisture,  so  that  a  copy  of  it  may  be  produced  even  after  the  original 
writing  has  become  dry,  by  being  simply  damped  and  pressed. 
The  following  formula  requires  no  press,  but  may  be  copied  by 
placing  a  damp,  sheet  of  copying-paper  on  the  writing  intended  to  be 
copied ;  above  this  sheet  of  copying-paper  a  sheet  of  ordinary  writing 
paper  must  be  placed,  and  then  pressed  with  a  paper-knife. 
COPYING-INK. 
Mix — Thirty  grains  of  extract  of  logwood, 
Seven  grains  crystal  soda, 
Half  an  ounce  of  water. 
Boil  till  dissolved ;  then,  while  stirring  well,  add  thirty  grains  of 
