Am&™\wrm'}     Paints,  Colors  and  their  Analysis.  1 5 1 
the  previously  black  sulphide  will  assume  a  beautiful  red  color.  The 
quicker  the  motion  the  lighter  and  more  fiery  will  be  the  shade.  Its 
high  price  prevents  an  extensive  use  of  this  pigment  in  painting. 
American  vermillion  is  formed  on  boiling  white  lead  with  a  solution 
of  potassic  bichromate.  The  genuine  article  is  of  a  beautiful  red 
color,  which  resists  very  well  to  atmospheric  influences.  In  order  to 
hide  the  decrease  of  intensity  of  this  color,  resulting  from  excessive 
admixture  of  white  bodies,  it  is  now  often  brought  to  the  necessary 
shade  by  the  addition  of  anilin  dyes  or  corallin.  The  following  ana- 
lysis of  a  scarlet  shows  the  composition  of  this  class  of  paints  : 
Moisture,        .  .  .  .  .      0*250  per  cent. 
Organic  pigment,  ....  2*400 
Baric  sulphate,  46*500 
Basic  lead  chromate,  .  .  ■  .  20*093 
Plumbic  sulphate,  .  31*700 
100*943 
The  organic  pigment  was  extracted  with  alcohol,  and  the  beautifully 
colored  solution  left,  on  evaporation  in  a  watch  glass,  a  crystalline  crust 
having  a  green  metallic  lustre.  Further  tests  proved  it  to  be  corallin, 
soluble  in  alcohol  and  alkalies,  insoluble  in  water.  The  immense 
colorific  power  of  anilin  dyes  renders  it  possible  to  give  red  lead, 
Pb304,  'orange  mineral,  (Pb304)  xH-(PbO)  y  and  even  massicot,  PbO, 
a  beautiful  scarlet  shade.  These  "  dyed  pajnts "  fade  very  rapidly 
when  exposed  to  light  and  air,  but  keep  well  when  sold  in  hermetically 
sealed  tin  cans,  either  dry  or  in  oil. 
A  beautiful  red  pigment,  consisting  of  antimony  sulphide,  Sb2S3,  can 
be  obtained  by  boiling  antimony  chloride  with  sodic  hyposulphite,  when 
an  elegant  reaction  will  take  place,  resulting  finally  as  follows  : 
2SbCl3-h3Na2S203+3H20-=6HCl+3Na2S044-Sb2S3. 
E.  Kopp,  who  first  showed  that  the  red  precipitate  was  neither  oxy- 
chloride  nor  oxysulphide,  also  communicated  a  practical  method  for  its 
manufacture  on  a  large  scale.  The  by-products,  sodic  sulphate  and 
hydrochloric  acid,  could  easily  be  recovered,  and  the  latter  utilized 
again  to  convert  the  black  native  antimony-sulphide  into  the  desired 
1  Orange  mineral  is  the  product  of  calcination  of  white. lead,  at  a  moderate  tem- 
perature, with  free  admission  of  air.  It  is  made  from  the  sweepings  of  white  lead 
works. 
