271 
CONTRIBUTIONS    TO    ECONOMIC    GEOLOGY,   L906.   PART    I. 
oil  samples  bleached  out  very  rapidly  after  treatment  if  exposed  to 
light,  and  the  amount  of  bleaching  varied  in  different  samples.  The 
method  of  comparison  adopted  was  as  follows:  Twenty-one  samples 
of  oil  were  selected  which  had  stood  in  the  light  long  enough  to  have 
reached  a  condition  of  stability,  and  which  showed  a  progressive 
range  of  color  from  the  lightest  to  the  darkest  oil  on  hand.  These 
samples  were  contained  in  glass  vials  of  uniform  size,  were  kept  in  a 
dark  box,  and  were  numbered  from  1  to  21,  No.  1  being  Fairbanks 
standard  white  oil,  which  had  stood  in  the  light  several  years  and  No. 
21  Fairbank's  crude  yellow  oil,  kept  in  the  dark  so  that  it  had  not  lost 
any  of  its  depth  of  color.  The  samples  tested  were  then  placed  in 
similar  vials,  compared  with  the  standards  against  a  sheet  of  white 
paper,  and  the  number  of  the  standard  most  nearly  agreeing  with  it 
in  shade  was  taken  as  it s  color  value.  This  comparison  was  always 
made  immediately  after  filtration,  before  the  oil  had  been  exposed  to 
light.  After  standing  over  night  in  the  dark  the  sample  was  com- 
pared again,  and  a  third  time  after  standing  in  the  light  for  two 
weeks.  Tin-  method  of  comparison  proved  very  satisfactory,  and 
there  was  no  evidence  of  any  change  in  the  standards  on  keeping. 
The  only  weakness  i)['  the  method  lies  in  the  fact  that  the  members  of 
the  color  series  do  not  vary  uniformly  in  the  amount  of  color  con- 
tained, and  hence  these  comparisons  can  give  no  Information  as  to 
the  absolute  percentage  of  color  removed. 
The  results  of  the  oil  tests  are  grouped  in  Table  .">,  which  does  not 
include,  however,  a  number  of  the  first  tests  that  were  considered 
unreliable.  It  .should  be  noted  that  standards  Nos.  19,  20,  and  21  are 
all  crude  yellow  oils  untreated,  and  that  no  bleaching  action  is  indi- 
cated with  any  certainty  unless  the  color  of  the  treated  sample  falls 
to  Is  or  l(  ss 
T  M.I    I 
Results  of  oil  tests  of  fuller's  earth  and  other  materials. 
\!  iteriaLa 
<  lolor  \  alue  of  oil. 
Imme- 
diately 
after  Bl- 
i  ration. 
All.T 
standing 
12  In. ins 
in  dark. 
Vfter 
standing 
2  weeks  in 
light. 
1 
1  i  i.i.i  r's   i  \i:  m. 
Owl 
L2 
L2 
13 
13 
12 
19 
„ 
11 
12 
12 
12 
13 
12 
19 
12 
11 
2 
Fairbank.  . 
;{ 
■\ 
■' 
4 
3 
", 
Dried: 
Rimer  A   Amend    « 1  ri« •<  1  .-it   14(1°  C 
2 
6 
Fairbank,  ignited  al  red  heal  tor  1J  hours 
Extracted  with  hot  dilute  lici  (1   2 
Owl 
185 
8 
Fairbank 
1J 
o  Fuller's  earths:  Owl,  from  Owl  Cigar  Co.,  Quincy,  Fki.;  Fairbank,  earth  at  present  used  by  N,  K. 
Fairbank  Co.,  Chicago,  III.,  received  in  June,  190*.;  Eimer  <&  Amend,  from  Eimer  &  Amend,  New  York, 
N.  V.  Pipeclay  (sample  from  Eimer  <v  Vmend),  nearly  pure  kaolinite,  as  shown  by  the  rational  analy- 
sis—kaolin,  91.51;  orthoclase,  7.61;  quartz,  0.88  which  is  calculated  from  the  analysis  given  in  Table  3. 
Clay,  a  residual  limestone  clay  from  a  bank  in  Staunton,  Va.  Analyses  of  most  oi  these  materials  will 
be  found  in  Table  3  (p.  272). 
