464       Presence  of  Albumen  in  Neutral  Fats,  etc.  {^tt'Sra™' 
the  risk  of  explosion  was  great.  When  they  were  decomposed  by 
sulphuric  (or  any  other  strong)  acid,  as  was  usually  the  case  in  Eng- 
land, much  of  the  fat  was  lost  by  being  charred  and  burnt,  and  the 
remainder  was  so  black  that  it  was  necessary  to  distil  it  to  render  it 
good  enough  in  color  for  manufacturing  purposes.  The  risk  of  fire, 
and  of  explosion  in  this  operation  was  considerable,  and  the  expense 
great.  Professor  Bock  had  shown  that  most  neutral  fats  were  made 
up  of  minute  globules  of  fat,  surrounded  by  albuminous  envelopes, 
which  form  1  to  1*5  per  cent,  of  the  weight  of  the  fat,  and  he  consid- 
ered that  the  excess  of  alkali,  of  pressure,  or  of  heat  required  to  de- 
compose fats,  was  really  used  in  the  destruction  and  removal  of  these 
albuminous  envelopes,  which  also  attracted  to  themselves  the  coloring 
matters  contained  in  the  fat,  or  produced  therein  during  its  decompo- 
sition. The  existence  of  the  albumen  could  be  demonstrated  in  the 
laboratory  by  dissolving  the  fat  in  ether  or  benzol,  and  precipitating 
the  solution  by  water,  or  by  boiling  the  fat  on  a  strong  solution  of  ox- 
alic acid.  In  both  cases  the  albuminous  envelopes  collected  at  the 
plane  of  junction  of  the  two  liquids.  In  Professor  Bock's  process  the 
albuminous  envelopes  were  broken  and  partly  destroyed  by  the  ac- 
tion, for  a  limited  time,  and  at  a  given  temperature,  of  a  small  quan- 
tity of  strong  sulphuric  acid.  The  neutral  fat  then  poured  out  from 
the  envelopes  in  a  state  ready  for  decomposition  by  water  in  open 
tanks,  an  operation  which  required  several  hours  for  its  complete  per- 
formance. Its  progress  was  judged  of  by  microscopical  examination 
of  the  crystals  of  the  fat,  or  fatty  acid,  co-formed  by  slowly  cooling  a 
thin  layer  upon  a  glass  slip.  When  it  was  completed,  the  glycerin, 
which  was  dissolved  in  the  water  used  for  the  decomposition,  was 
drawn  off,  purified,  and  concentrated  for  sale.  The  fatty  acids, 
amounting  to  94  per  cent,  of  the  original  fat,  were  at  this  stage  of  a 
very  brown  or  blackish  color.  The  next  operation  was  to  eliminate 
the  albuminous  envelopes,  and  with  them  most  of  the  coloring  matters. 
This  was  done  by  submitting  the  fatty  acids  in  open  tanks  to  the  ac- 
tion of  dilute  solutions  of  certain  oxidizing  agents,  by  which  the  black 
matters  were  partly  oxidized,  and  their  specific  gravity  greatly  in- 
creased, so  that  when  the  oxidation  had  proceeded  far  enough  they 
readily  subsided  to  the  bottom  of  the  tank,  leaving  the  fatty  acids 
comparatively  good  in  color.*    After  two  or  three  washings  with  di- 
*  The  oxidizing  agents  that  had  been  employed  were — the  three  strong  min- 
eral acids,  sulphuric,  nitric,  and  hydrochloric,  permanganate  and  bichromate 
of  potash  and  hypochlorite  of  lime. 
