400  Analytical  Researches  and  Investigations.   { a^""  t  i88->'^°'' 
it  is  half  filled  with  water  and  the  contents  of  the  capsule  then  poured 
upon  it,  being  careful  that  the  niveau  of  the  liquid  never  exceeds  two- 
thirds  of  the  height  of  the  filter.  The  capsnle  and  the  rod  are  then 
washed  with  hot  water,  which  removes  perfectly  the  fatty  acids,  after 
which  the  w^ashing  of  these  acids  is  continued  on  the  filter  until  the 
washings  have  no  longer  an  acid  reaction ;  it  requires  about  f  liter  of 
w^ater  to  attain  this  result,  but  no  risk  is  involved  of  the  fatty  acids 
passing  through  the  wet  filter.  After  washing,  the  funnel  is  placed  in 
cold  water,  and  as  soon  as  the  acids  have  solidified  the  filter  is  dried 
at  100°C.  in  a  tared  beaker  until  the  weight  remains  constant,  which 
is  attained  in  about  two  hours.  In  this  way  the  weight  of  the  non- 
volatile fatty  acids,  insoluble  in  water,  is  determined. 
Butter  yields  by  this  procedure  from  86'5  to  87*5  and  sometimes  88 
per  cent,  of  fatty  acids.  The  animal  fats  which  serve  for  adulteration 
contain  95'5  per  cent.,  consequently  an  excess  of  95*5 — 87'5=8  j^er 
cent,  by  reason  of  the  complete  absence  of  soluble  or  volatile  fatty 
acids.  If,  then,  in  analyzing  a  butter,  it  is  found  for  the  amount  of 
acids  a  number  exceeding  87*5,  for  example  91  per  cent.,  being  an 
excess  of  3'5,  it  must  be  concluded  that  the  butter  is  adulterated,  and 
that  it  has  received,  as  a  minimum,  an  addition  of  ^^^  +  100=43  per 
cent  of  foreign  fat.    (See    xVmer.  Jour.  Phar.,"  1878,  p.  257,  258.) 
Determination  of  the  Water, — Ten  ^rams  of  butter  are  dissolved  in 
thirty  cubic  centimeters  of  petroleum,  having  a  specific  gravity  of  0*69 
ann  boiling  at  80  to  110°C.  The  liquid  which  unites  at  the  bottom  is 
collected  by  the  aid  of  a  separating  funnel  and  measured  in- a  tube 
divided  into  tenths  of  a  cubic  centimeter;  each  division  indicates  1 
per  cent,  of  water  and  of  impurities  ;  good  butter  contains  from  10  to  14 
per  cent,  of  water ;  in  this  way  one  may  recognize  also  the  pres(ince  of 
substances  slightly  soluble  in  water,  added  for  the  purpose  of  adulter- 
ation, and  the  salt  mixed  with  the  butter  for  its  preservation.  The 
separated  water  contains  also  a  portion  of  tlie  dissolved  foreign  salts : 
alum,  borax,  soluble  glass,  etc. 
The  butter  may  also  be  dried  at  110°C.  and  the  product  extracted  by 
a  light  petroleum,  boiling  below  100°C.  The  residue  consists  of  salt, 
the  casein  and  lactose,  the  latter  of  which  may  be  estimated  by 
Fell  ling's  solution.  Butter  is  colored  with  ctircuma  or  victoria  yel- 
low, with  chromate  of  lead,  yellow  coralline,  or  the  nitrous  derivatives 
of  saffron  and  annotto.  In  order  to  recognize  the  presence  of  these 
-coloring  matters  it  Ls  necessary  to  make  comparative  reactions  with  the 
