Preparation  of  Sample  for  Analysis.  The  milk  should  be  trans-
ferred from  the  bottle  in  which  it  is  received  to  a  large  beaker  and
poured  back  and  forth  several  times  until  it  is  uniform.  In  case  of
milk  received  in  milk  cans,  the  total  amount  should  be  poured  from
one  can  to  another  the  same  as  in  a  bottle  of  milk.
Sour  Milk3  may  be  re-emulsified  by  the  use  of  ammonia.  Add  a
sufficient  quantity  of  concentrated  ammonia  to  the  curdled  milk  to
restore  it  to  its  natural  limpid  emulsified  condition.  The  milk  will
then  be  in  a  condition  for  analysis.
The  solids  from  milk  treated  with  ammonia  will  appear  darker  than
untreated  milk,  and  become  brown  like  partially  caramelized  sugar;
however,  this  does  not  reduce  the  percentage  of  solids  to  any  marked
extent  (about  0.2  per  cent,  generally).  The  fat  may  be  determined
either  by  volumetric  or  gravimetric  methods  in  the  usual  manner.
1  Analyst,  1900,  25,  231.
2  Analyst,  1902,  27,  89.
8  Analyst,  1885,  10,  100.
DAIRY  PRODUCTS.  183

If  any  appreciable  amount  of  'ammonia  is  used  in  neutralizing  the
milk,  a  correction  should  be  made  for  the  increase  in  volume.
Ordinarily  the  determination  of  water,  solids,  fat  and  ash  is  all
that  is  necessary,  except  in  cases  where  bacteriological  examinations
are  required.
In  a  complete  analysis  of  milk  the  chemical  examination  would
include  the  following:

Specific  gravity.
Solids.
Ash.
Fat.
Lactose.     (Milk  sugar.)

Protein  compounds.     (Casein  and  Albumin.)

Preservatives.
Coloring.
Specific  gravity  is  generally  determined  by  a  Quevenne  lactometer,
although  a  pycnometer  should  be  used  for  absolute  work.  In  either
case  it  should  be  taken  at  a  certain  temperature,  say  25°  C.  The
average  specific  gravity  of  unadulterated  milk  should  be  near  1.0320.
