478 
The  Salts  of  MIL 
/Am.  Jour.  Pharm. 
\      Sept..  1889. 
Haruruarsten  (Jahresber.  fur  Tierchem.,  1874,  135)  considers  that 
casein  acts  as  a  solvent  for  calcium  phosphate,  whilst  Eugling  (1885) 
believes  that  the  casein  enters  into  combination  with  tri-calcium 
phosphate,  a  view  which  is  also  held  by  Schaffer  (Landw.  Jahrb. 
d.  Schweiz,  1887).  Eugling' s  theory  is  rejected  as  being  based 
on  erroneous  suppositions. 
Determinations  of  lime  and  phosphoric  acid  were  made  in  milk,  in 
the  serum  of  milk  filtered  through  porous  cells,  and  in  the  insoluble 
portion  of  milk.  36  to  56  per  cent,  of  the  phosphoric  acid,  and  53  to 
72  per  cent,  of  the  lime  are  undissolved,  being  probably  in  suspension. 
The  undissolved  lime  (not  in  casein)  is  in  combination  with  phosphoric 
acid  as  a  mixture  of  di-  and  tri-calcium  phosphates  (compare  Duclaux, 
Ann.  inst.  not.  agronom.,  viii).  It  was  found  that  of  the  undissolved 
phosphoric  acid  and  lime,  44  to  72  per  cent,  and  26  to  67  per  cent, 
respectively,  could  be  dissolved  in  carbonic  or  acetic  acid. 
Eugling  [loc.  cit.)  states  that  the  calcium  salts  in  milk  are  not  pre- 
cipitated by  ammonium  oxalate.  The  author  finds  that  85  per  cent, 
of  the  calcium  is  precipitated  ;  at  the  same  time  there  is  a  change  in 
the  appearance  of  the  milk  which  indicates  that  the  reactions  which 
take  place  extend  to  the  casein,  probably  with  formation  of  an  ammo- 
nium salt.  Serum  obtained  by  sodium  chloride,  and  that  obtained  by 
alcohol,  are  both  precipitated  by  ammonium  oxalate,  just  like  the 
serum  produced  by  rennet.  Eugling's  negative  result  with  alcohol 
serum  was,  no  doubt,  due  to  the  presence  of  alcohol,  which  is  shown 
to  prevent  the  formation  of  calcium  oxalate. 
With  regard  to  the  decrease  in  the  acidity  of  milk,  observed  by 
Schaffer  (Joe.  cit.)  to  be  produced  by  the  action  of  rennet,  it  is  found 
that  if  the  casein  is  made  to  separate  in  a  finely  divided  state,  so  that 
the  whole  of  it  may  come  into  contact  with  the  alkali,  and  if,  at  the 
same  time,  unnecessary  dilution  of  the  curdled  milk  is  avoided,  the 
acidity  of  the  milk  remains  constant.  Boiling  has  no  effect  on  the 
acidity  of  the  milk. 
The  belief  that  casein  in  milk  is  in  combination  with  calcium  phos- 
phate originated  in  Hanimarsten's  observation  that  the  curdling  of 
milk  by  rennet  is  connected  with  the  presence  of  calcium  salts. 
Hamrnarsten  showed  that  other  alkaline  earths  may  be  substituted  for 
lime,  and  that  they  may  be  present  as  sulphates  and  carbonates,  and 
still  have  the  same  action  (compare  Lundberg,  Jahresb.  Tierchem.,  1876, 
11).    It  is  shown  that  calcium  phosphate  suspended  in  a  casein  solu- 
