Am'j$l\lX™'}     P^nts,  Colors  and  their  Analysis.  155 
will  stand  an  admixture  of  50  to  75  per,  cent,  of  white  pulverulent 
substances,  as,  for  instance,  barytes,  whitening,  etc.,  without  assuming  a 
grey  appearance.  The  different  grey  shades  are  obtained  by  mixing 
and  grinding  black  pigments  with  large  quantities  of  white  substances 
as  theabove  mentioned.  Zinc  dust — a  by-product  of  the  zinc  distillation, 
the  well-known  reducing  agent  in  chemistry — is  also  used  as  a  grey 
paint.  A  sample  of  this  substance,  which,  spontaneously  ignited 
through  the  action  of  moisture,  had  the  following  composition  (vide 
Berg  und  Hiittenmannische  Zeitung,  1877)  : 
Zinc,      .....  40  o  per  cent. 
Lead,  .  .  .  .  .2*5 
Cadmium,  ....  40 
Zinc  oxide,  .....  50^0 
Zinc  carbonate  and  dust,  .  .  3-5 
IOO'O 
Several  samples  analyzed  by  me  contained  in  toto  63*637,  79*978,. 
54*727  per  cent,  of  zinc. 
It  would  require  too  much  space  to  treat  of  all  the  numerous  pig- 
ments of  less  commercial  importance  ;  therefore,  only  those  have  been 
considered  which  are  most  frequently  met  with  in  the  market.  Con- 
cerning the  different  chemicals  used  in  the  manufacture  of  paints  it 
may  be  stated  that  large  colorworks  very  often  prepare  their  own  supplies,, 
as,  for  instance,  acetic  acid,  potassic  ferrocyanide,  alum,  copper  sul- 
phate, the  different  lead  salts,  etc.  As  in  many  instances  the  solutions 
of  freshly  formed  compounds  can  at  once  be  applied  without  previous 
evaporation  and  crystalization,  many  colors  can  thus  be  far  cheaper 
prepared  than  by  those  concerns  who  buy  their  supplies  and  produce 
the  solutions  from  the  crystallized  chemicals.  A  similar  saving  is  also 
caused  by  the  use  of  ct  pulps  "  in  producing  color  mixtures. 
Analysis  of  Paints.— The  sample  to  be  analyzed  may  be  in  the 
dry  state,  ground  in  oil  or  in  liquid  form,  ready  for  use.  In  the  latter 
cases  the  fatty  or  resinous  portions  of  the  paint  are  extracted  with 
benzin,  alcohol  and  ether,  which  leave  the  pigment  in  form  of  a 
powder  suitable  for  analysis.  In  some  cases  the  additions  may  be 
removed  by  simple  ignition  ;  however,  as  reductions  are  very  apt  to 
take  place,  this  process  recommends  itself  only  in  a  limited  number  of 
cases.  If  a  complete  analysis  of  a  liquid  paint  is  required,  whereby,, 
not  only  the  pigment  but  also  the  vehicle,  the  different  oils,  the  quan- 
