"^""■/eb'-ifz^ }    ^^^^^  of  Vegetable  and  Animal  Oils,  7  5 
on  fifteen  different  oils.  Cotton-seed  oil  and  olein  from  tallow  are 
omitted,  as  well  as  fifty  other  of  minor  importance. 
Heidenreich,  Penot  and  Marchand  have  also  proposed  color  tests 
from  the  reaction  of  pure  sulphuric  acid  on  oils,  but,  like  those  of  Cal- 
vert, thev  are  open  to  doubt  and  uncertainty,  the  coloration  often  de- 
pending on  the  accidental  impurities  of  the  oil. 
There  is  a  great  difference  in  the  amount  of  heat  produced  on  mixing 
one  part  of  sulphuric  ac'd  with  three  parts  of  oil  ;  the  gain  in  tempera- 
ture is  100°  where  rape-seed  oil  is  used,  as  compared  with  68°,  when 
olive  oil  is  experimented  upon.  A  method  based  on  this  principle  was 
suggested  by  Marmene  and  elaborated  by  Fehling  ;  it  is  easy  of  execu- 
tion and  interesting  in  results. 
The  relative  viscosities  of  the  fatty  oils  is  determined  by  the  time 
required  for  a  given  quantity  of  each  oil  to  flow  from  a  pipette  which 
is  heated  to  120°  F.  by  being  surrounded  by  a  glass  tube  into  which 
steam  is  passed.  In  an  experiment  made  by  Mr.  Coleman,  German 
refined  rape  required  8J  minutes  ;  olive,  8J  minutes  ;  tallow,  min- 
utes ;  lard  oil,  7  minutes  ;  cotton  seed,  7  minutes  ;  sperm,  5  minutes. 
Spontaneous  combustion  ensues  when  a  handful  of  cotton  waste  is 
imbued  with  oil  and  placed  in  an  air  bath  at  130°  to  200°  F.  Boiled 
linseed  required  i\  hour;  raw  linseed,  4  hours;  lard  oil,  4  hours;  re- 
fined rape,  about  9  hours.  Mr.  Gellatly  found  that  an  admixture  of 
20  per  cent,  of  mineral  oil  retarded  combustion,  and  50  per  cent,  pre- 
vented it  entirely. 
There  are  three  practical  mothods  of  judging  of  the  drying  properties 
of  oils  :  I.  Nitrate  of  mercury,  which  indicates  by  the  consistency  of 
the  mass  subjected  to  the  reaction.  Resin  oil,  mineral  oil,  and  the  dry- 
ing oils  proper,  refuse  to  solidify.  2.  Comparing  a  sample  under  ex- 
amination, heated  in  a  shallow  capsule  to  200°  F.,  with  a  light  quantity 
of  oil  known  to  be  pure.  3.  Imbuing  thick  white  blotting  paper  with 
the  oil  under  examination,  and  comparing  by  a  similar  experiment  with 
oil  known  to  be  pure,  say  at  a  temperatnre  of  150°  or  200°  for  some 
hours,  or  at  ordinary  temperatures  for  some  days. 
The  specific  gravity  of  oils  has  been  carefully  determined,  and  is  of 
some  consequence.  To  be  of  value  the  specific  gravity  should  be  care- 
fully taken  at  a  temperature  of  60^  F.  The  oleometer  should  be 
marked  with  ordinary  specific  grayity  degrees,  water  being  1,000,  and 
the  space  allowed  on  the  stem,  for  each  degree  should  not  be  less  than 
