A  janua^fi898rm*}     Analysis  of  the  Gastric  Contents.  41 
D.  Ten  cubic  centimetres  contents  titrated  with  NaOH  failed  to 
give  red  color  with  phloroglucin-vanillin,  first,  on  addition  of  3-2 
c.c.  NaOH  solution  —  responded  with  3-1  c.c.  .  •  .  Total  free  HC1  — 
3-1  X  '00365  X  100  =  1-13  grammes  per  mille. 
E.  Total  hydrochloric  acid  =  C  +  D,  that  is,  077  -f  1-13=  190 
gramme  per  mille. 
F.  Total  acidity  due  to  organic  acids  plus  acid  salts  =  B  —  D> 
that  is,  178  —  1-13  =  0-65  gramme  per  mille.46 
The  whole  process  of  quantitative  determination  by  this  method 
can  be  accomplished  with  simple  apparatus  within  twenty  minutes. 
The  results,  though  not  of  absolute  accuracy,  are  accurate  for 
comparative  work.  For  example,  the  delicacy  of  the  test  for  free 
HC1  is  -05  gramme  per  mille.  The  total  free  HC1  is  thus  for  3-1 
c.c.  NaOH  solution  not  1-13  per  mille,  but  1-13  -f  0  05  per  mille. 
Also  the  error  incident  upon  the  judgment  of  colors  must  affect  the 
results  in  this  method  for  absolute  work.  The  above  sources  of 
error  are,  however,  constant  in  comparative  work,  and  thus  do 
not  affect  the  results. 
A  certain  amount  of  the  secreted  HC1  combines  with  the  phos- 
phates of  the  food,  forming  acid  phosphates,  which  contribute  to 
the  sum  of  the  total  acidity  of  the  contents.  In  some  cases  it  may 
be  useful  to  estimate  these  total  acid  salts  and  the  total  organic  acids 
separately.  This  may  be  accomplished  by  the  addition  of  the  fol- 
lowing method  (Leo's  method)  of  estimating  the  total  acid  salts  to 
the  scheme  of  analysis  already  given.47 
To  1 5  c.c.  contents  add  1  gramme  dry  powdered  CaCOs ;  shake; 
filter.  Measure  off  10  c.c.  of  filtrate;  pass  a  stream  of  hot  air 
through  it  to  carry  off  the  C02 ;  add  5  c.c.  CaCl2,  add  one  drop  of 
phenolthalein,  and  titrate  with  decinormal  soda  solution.  The  total 
acidity  of  this  last  filtrate  divided  by  2  is  the  total  acid  salts  con- 
tained in  the  10  c.c.  of  contents.  The  CaC03  unites  with  all  the 
acid  elements  of  the  contents  save  the  acid  salts,  forming  of  the 
HC1  calcic  chloride,  of  the  lactic  acid  lactate  of  calcium,  etc.  In  the 
presence  of  the  CaCl2  thus  formed  twice  the  amount  of  decinormal 
46  If  the  acid  salts  are  computed  by  the  method  given  below,  we  get  the  fol- 
lowing addition  to  the  above  record  :  G  total  acid  salts  subtracted  from  B2 
(total  free  acids  andplus  acid  salts  in  mixture  with  CaCl2  =  total  free  acids  (H). 
Subtract  total  free  HC1  D  from  total  free  acids  (H)  —  total  organic  acids  (K). 
47  Leo  :  Krankheiten  der  Verdauungs  Organ,  Berlin,  1890. 
