PROPERTIES    AND    TESTS    OF    FULLER 's    EARTH. 
273 
PHYSICAL    TESTS. 
Plasticity  is  defined  as  that  property  which  permits  clay  to  be 
molded  in  any  desired  form  when  wet,  the  shape  being  retained  when 
dry."  .  F.  F.  Grout b  says  that  "Plasticity  may  be  considered  as 
involving  two  variable  factors — (1)  amount  of  possible  flow  before 
rupture;   (2)  resistance  to  flow  or  deformation." 
According  to  either  of  these  definitions  the  four  samples  of  fuller's 
earth  which  I  have  tested  are  most  decidedly  plastic,  in  spite  of  the 
fact  that  nonplasticity  is  given  as  one  of  the  distinguishing  qualities 
of  this  material  by  almost  every  writer  on  the  subject. 
In  making  these  tests  small  pats  of  wet  earth  were  allowed  to  air 
dry,  and  portions  were  heated  to  redness  to  note  their  behavior.  It 
was  found  that  the  fuller's  earths  require  much  water  to  bring  them 
to  the  plastic  state,  apparently  more  than  the  kaolin,  although  the 
quantity  used  was  not  measured.  The  fuller's  earth  also  formed  a 
much  more  sticky  mass  than  the  other  materials  tried,  and  had  a 
more  soapy  or  greasy  feel.  Table  4  gives  the  results  of  these  tests  in 
convenient  form. 
Table 
4. — Physical 
properties  <>J\ 
'uller's  earths, 
etc. 
Materi.ii. 
Relative 
amount  of  wa- 
ter to  bring  to 
plastic  state. 
Plasticity. 
Coherence 
when  dry. 
Strength  when  burned. 
Owl  fuller's  earth  a 
Very  great .  .  . 
Very  strong.  . 
do 
Very  hard  and  strong. 
Do. 
do 
do 
Much 
...do. . 
do.  .. 
...do... 
Do. 
earth. c 
Queen  fuller's  earth  d 
..do. .. 
do... 
Do. 
do.  .. 
...do... 
Do. 
Much  less    
Very  soft 
Fairbank  fuller's  earth   in- 
soluble in  II2S04. 
Less 
Less 
Did   not   crumble,    but 
very  soft. 
a  Sample  from  Owl  Cigar  Co.,  Quincy,  Fla. 
b  Sample  from  N.  K.  Fairbank  Co.,  Chicago,  111. 
e  Sample  from  Eimer  &  Amend,  New  York,  N.  Y. 
d  Sample  from  Queen  &  Co.,  Philadelphia,  Pa. 
e  Pure  china  clay  from  Augusta  County,  Va. 
OIL    TESTS. 
In  making  the  oil  tests  50  c.  c.  of  cotton-seed  oil  were  introduced 
into  a  stout  comparison  tube  of  about  120  c.  c.  capacity.  This  was 
then  placed  in  an  oil  bath  and  heated  to  a  temperature  of  220°  F.; 
2.5  grams  of  the  earth  to  be  tested  were  then  poured  into  the  tube, 
which  was  at  once  removed  from  the  oil  bath,  closed  with  a  rubber 
stopper,  and  shaken  for  five  minutes.  At  the  end  of  this  time  the 
contents  were  poured  into  a  creased  filter  in  a  hot-water  funnel,  and 
the  filtered  oil  was  received  in  a  tube  protected  from  the  light  by  a 
cardboard  case.     This  protection  was  found  necessary  because  certain 
aRies,  H.,  Clays  and  clay  industries  of  New  Jersey:  Final  Repts.  New  Jersey  Geol.  Survey,  vol.  G, 
1904,  p.  81. 
&  Clays,  Limes,  and  Cements,  West  Virginia  Geol.  Survey,  1906,  p.  41. 
