Am.  Jour.  Pharni.  \ 
November,  1904.  j 
Theory  of  Indicators,  etc. 
515 
represents  the  end  point  of  free  and  totally  dissociated  hydrochloric 
acid  may  be  proved  by  determining  the  osmotic  pressure  of  the 
stomach  contents  in  a  fresh  state,  after  neutralization  to  the  drops' 
end  point  to  the  alizarin  end  point,  and  to  the  phenolphthalein  end 
point.  In  the  first  period  up  to  the  drops'  end  point  the  osmotic 
pressure  cannot  be  found  even  approximately  by  summing  those  of 
its  constituent  solutions,  a  simple  calculation  showing  that  free 
hydrochloric  acid  has  been  neutralized  by  soda,  thus  forming  only 
two  ions  and  a  slightly  dissociated  molecule  in  the  place  of  four. 
After  the  phloroglucinvanillin  end  point,  the  determinations  of  the 
freezing  point  indicate  a  reaction  between  ammonium  chloride  or 
some  similar  body  and  soda,  which,  as  would  be  anticipated,  fails  to 
result  in  as  large  a  diminution  in  the  osmotic  pressure  as  is  ooserved 
in  the  first  portion. 
The  observation  that  the  phosphotungstic  filtrates  obtained  from 
peptic  digestion  mixtures  may  reach  very  considerable  proportions 
in  spite  of  the  absence  of  leucin,  tyrosin  and  all  final  products  of 
disintegration  of  proteids,  must  be  attributed,  in  all  probability,  to 
the  presence  in  the  mixture  of  derivatives  of  these  mono-amido  acids 
possessing  at  least  twice  as  large  a  complex.  It  is  very  probable 
that  this  particular  mono-amido  acid  grouping,  even  in  relatively 
complex  molecules,  may  lead  to  a  differentiation  of  those  compounds 
possessing  it  from  those  possessed  of  di-amido  acid  grouping,  which 
are  precipitated  by  phosphotungstic  acid. 
The  results  obtained  with  artificial  peptic  digestion  mixtures  and 
normal  and  pathological  stomach  contents  may  be  summarized  as 
follows : 
(1)  In  a  normal  peptic  digestion  that  has  only  been  allowed  to 
run  three  or  four  hours  after  a  purely  proteid  or  an  Ewald  test 
meal  (and  allowing  for  the  effect  of  phosphates  and  carbonic  acid), 
the  phenolphthalein  end  point  gives  an  accurate  estimate  of  the 
total  available  hydrochloric  acid  present  in  the  stomach,  either  free 
or  combined  with  proteids. 
(2)  The  end  point  to  drops  of  phloroglucinvanillin  gives  a  fair 
estimate  of  the  actual  free  hydrochloric  acid. 
(3)  The  range  from  phloroglucinvanillin  drops  to  the  phenol- 
phthalein end  point,  after  allowing  for  phosphates,  is  a  function  of 
the  proteids  present  in  the  mixture  and  the  extent  of  their  hydroly- 
sis or  decomposition. 
