AFebS^,Pi9ir'}      Fat  Decomposition  and  Glycerin.  77 
fatty  acid,  shut  off  steam,  turn  on  jet,  and  add  barium  carbonate 
mixed  with  a  little  water  in  proportion  of  %  lb.  barium  to  every 
500  lbs.  stock.  In  a  few  moments  take  a  sample  from  cock  in  side 
of  tank  and  test  if  water  is  neutral  to  methyl  orange.  If  it  is, 
steam  may  be  turned  off  jet  and  water  allowed  to  settle.  The  fatty 
acids  are  now  perfectly  stable  and  may  be  stored  in  wood  until 
wanted. 
The  glycerin  waters  are  treated  with  milk  of  lime  until  dis- 
tinctly alkaline,  the  liquor  being  kept  agitated  to  prevent  settling 
of  the  calcium  sulphate.  The  treated  glycerin  water,  or  sweet  water 
as  it  is  designated,  is  pumped  through  a  filter  press  into  a  storage 
tank  from  which  it  is  drawn  for  evaporating  into  crude.  This  can 
be  done  in  an  open  tank  with  closed  steam  coil  or  in  a  vacuum 
apparatus  either  single,  double  or  triple  effect,  to  340  B,  which  for 
Twitchell  crude  is  90  per  cent,  absolute  glycerin  and  80  per  cent, 
absolute  glycerin  for  soap  lye  crude.  All  crudes  are  analyzed  before 
refining,  the  acetin  method  being  generally  used  by  the  large  refiners, 
experience  showing  the  results  obtained  are  more  nearly  accurate 
than  by  the  bichromate  method. 
To  conduct  this  test  take:  1^2  Gm.  crude  glycerin;  10  Gm. 
anhydrous  soda  acetate ;  8  c.c.  acetic  anhydride.  Boil  under  reflex 
condenser  for  iy2  hours,  cool  a  little  and  dissolve  tri-acetin  formed 
in  50  c.c.  warm  water.  Do  this  while  still  under  reflex,  cool  and 
filter,  washing  filter  well,  add  phenolphthalein  to  filtrate  and  neu- 
tralize excess  of  acetic  acid  with  2  per  cent,  solution  NaOH,  taking 
great  care  not  to  run  over  end  point  or  let  solution  become  alkaline 
locally  while  adding  the  NaOH.  Then  add  an  excess  of  10  per 
cent,  solution  NaOH  and  boil  20  minutes.  Titrate  excess,  also 
run  blank  on  the  10  per  cent.  NaOH.  Titration  of  blank  minus 
titration  of  excess  divided  by  weight  of  sample,  multiplied  by  1.533, 
equals  per  cent  of  glycerin. 
The  following  yield  and  capacity  tests  (the  cost  test  for  obvious 
reasons  being  omitted)  will  indicate  how  thoroughly  a  plant  and 
laboratory  can  check  results. 
Cotton  foots.  .703,580  lbs.  Laboratory  test,  58.32  per  cent,  fatty  acid 
Reagent   17,812  lbs.    Laboratory  test,  75      per  cent,  fatty  acid 
This  shows  for  the  foots.  . .  .410,333  lbs.  fatty  acid 
and  for  the  reagent.  . .  .  13,359  lbs.  fatty  acid 
A  total  of  423,692  lbs.  fatty  acid  to  be  accounted  for. 
