152  Paints,  Colors  and  their  Analysis.  {AmA^X'x87h8arm* 
chloride  necessary  for  this  manufacture.  The  fact,  however,  that  this 
color  is  readily  influenced  by  the  atmosphere,  etc.,  has  so  far  prevented 
a  more  extensive  application. 
Green  Colors  and  Paints. — These  are  either  green  colored  chem- 
ical combinations  like  Paris-green,  Scheele's  green  and  chromic  oxide, 
or  secondly,  mixtures  of  blue  and  yellow  pigments  like  the  so-called 
chrome-greens,  which  consist  of  lead  chromate  and  Berlin-blue. 
Paris-green,  aceto-arsenite  of  copper,  =C4H604Cu-f  3  (As204Cu) 
is  one  of  the  most  beautiful  pigments,  which,  however,  on  account  of 
its  extreme  poisonous  qualities,  is  very  limitedly  used  in  painting.  It 
is  the  more  astonishing,  therefore,  to  find  this  very  pigment  often  used 
for  staining  wall-paper  and  fancy  paper  for  confectioners'  use  (see  my 
article  "  Dangerous  Candy,"  vol.  49,  1877,  p.  14,  of  this  journal). 
Muspratt  gives  the  following  analysis  of  this  pigment : 
Arsenious  acid,  As203,  .  .    58  65  per  cent. 
Cupric  oxidej  CuO,  .  .  31*29 
Acetic  acid,  C2H462,  .  .  .  10*06 
Immense  quantities  of  Paris-green  are  used  to  kill  potato-bugs.  It 
is  often  adulterated  with  gypsum,  which  will  be  left  as  insoluble  resi- 
due on  addition  of  ammonia,  in  which  the  pure  pigment  dissolves 
entirely. 
Scheele's  Green  is  cupric  arsenite,  and  also  highly  poisonous.  It  is 
darker  and  of  a  less  bright  and  elegant  shade  than  the  former. 
Guignet  Green,  chiefly  consisting  of  chromic  oxyhydrate  or  oxyborate, 
is  perfectly  harmless,  and  forms  on  fusing  potassic  bichromate  with 
boric  acid,  the  mass  being  subsequently  extracted  with  hot  water,  when 
the  pigment  will  be  left  as  a  beautiful  green  powder,  which  is  of  more 
importance  in  calico  printing  than  in  the  manufacture  of  paints. 
The  most  prominent  representatives  of  the  second  class  are  the 
numerous  shades  of  varying  mixtures  of  Prussian-blue  and  lead  chro- 
mate, which,  in  regard  to  their  manufacture  as  well  as  to  their  analysis, 
are  the  most  complicated  colors  in  the  market.  Almost  every  color- 
work  and,  doubtless,  every  color-maker,  pretends  to  have  some  secrets 
about  the  "  greens.''  Very  often  these  colors  contain  tartaric,  oxalic 
or  citric  acid,  not  unfrequently  all  three  in  minute  quantities,  which  the 
color-maker  adds  when  the  green  precipitate  has  already  formed,  "  to 
improve  the  shade."  (?!)  It  would  require  too  much  space  to  dwell 
on  the  manufacture  of  chrome  greens,  and  it  therefore  may  suffice  to 
