AmAi0Xi^78rm'}     Paints,  Colors  and  their  Analysis.  149 
awhile,  take  a  sample  of  the  mixture,  while  the  remainder  is  treated  in 
the  above-mentioned  manner  for  about  half  an  hour  longer.  The  mixture 
now  exhibits  a  far  deeper  shade  than  the  sample  previously  taken,  with 
which  it  corresponds  in  composition,  so  that  the  uninitiated  will  hardly 
believe  that  both  are  formed  from  the  same  constituents,  in  the  same 
proportion.  1  per  cent.,  even  J-  per  cent.,  of  blue  with  99  to  99J  per 
cent,  of  whitening  or  u  zinc  "  (ZnO)  will  yet  form  a  fine  sky,  or  celes- 
tial, blue,  as  some  manufacturers  prefer  to  call  it.  Everybody  has 
seen  those  blue-painted  barrels  in  which  coal  oil  is  shipped.  An  ana- 
lysis of  said  paint  gave  the  following  result : 
Calcic  carbonate,  ....    59*032  per  cent. 
Sulphuric  acid,  ....  0*583 
Ferric  oxide  (from  blue),  .  .  .2  200 
Volatile  portion  of  the  blue,     .  .  ,  2*200 
Zinc  oxide,       .  .  .  .  .  36.120 
Lead,        ....  trace 
100*135 
The  white  paint  of  the  lid  of  these  barrels  analyzes  as  follows : 
Sulphuric  acid,  ....  12*546  per  cent. 
Lime  (as  sulphate),  .  ■  .  .  .  9*068 
Zinc  oxide,       .....  78  500 
Traces  of  alumina. 
ioo*i  14 
This  paint  had  been  ground  in  oil,  which  was  eliminated  by  ignition  ; 
the  calcic  sulphate,  CaS04,  therefore,  is  to  be  calculated  as  gypsum, 
CaS04-{-2H20,  which  approximately  leads  to  the  following  working 
formula:  Gypsum  (CaS04-f-2.H20)  =  25,  and  zinc  white  (ZnO)  = 
75  per  cent. 
The  following  analyses  of  "  coal  oil  "  blues  of  different  make  show 
that  they  all  contain  about  4  per  cent,  of  the  blue  pigment,  and  solely 
differ  in  quality  and  quantity  of  the  white  admixtures  : 
Ferric  oxide  (from  blue),               .              .              ,  2*023  per  cent. 
Volatile  portion  of  blue,          .              .              .  2*023 
Carbonic  acid,                 ...              .              .  25*232 
Silicic  acid,              ....  o  269 
Sulphuric  acid,               ....  1*048 
Lime,                                                  ,  35'2i5 
Magnesia,        .                                                        .  o*6oo 
Plumbic  oxide,          ....  1*987 
Oxide  zinc,       .....  31*538 
99'935 
