40  Analysts  of  the  Gastric  Contents.  {^Jg^fJjS^ 
To  ioo  c.c.  of  the  contents  add  a  decinormal  solution  of  hydro- 
chloric acid  until  the  test  for  free  HC1  with  phloroglucin-vanillin  is 
obtained.  Since  the  limits  of  the  Gunzburg  reaction  is  0  036 
gramme  per  mille  HC1  (that  is,  1  c.c.  decinormal  soda  solution  to 
100),  the  difference  between  this  figure  and  the  amount  of  decinor- 
mal soda  solution  used  represents  the  amount  of  combined  HC1 
present  in  the  100  c.c.  of  contents,  that  is,  the  total  hydrochloric 
acid  present.  For  example,  if  Gunzburg's  reaction  were  first  posi- 
tive after  the  addition  of  six-tenths  of  a  cubic  centimetre  decinormal 
HC1  solution  to  100  c.c.  contents,  then  1  —  0  6  =0-4  c.c.  one-tenth 
normal  HC1  is  the  amount  of  HC1  already  present  in  100  c.c.  of  con- 
tents. This  process  can  be  conducted  with  less  than  100  c.c,  if 
necessary. 
The  total  combined  acid  (c)  in  cases  where  no  free  HC1  is  present 
represents  the  sum  of  the  combined  hydrochloric  and  combined 
organic  acids.  Where  no  organic  acids  are  present  by  the  qualita- 
tive tests,  the  total  combined  acid  (c)  may  be  taken  approximately 
as  the  total  hydrochloric  acid  in  these  cases.45 
As  an  example  of  the  application  of  this  method,  I  give  the 
results  of  the  examination  of  the  contents  of  a  normal  stomach — 
contents  expressed  one  hour  after  an  Ewald  test  meal. 
Amount  of  contents,  160  c.c. 
Amount  of  filtrate,  85  c.c. 
A.  Ten  cubic  centimetres  mixed  contents  plus  two  guttse 
phenolthalein  gave  red  color  on  addition  of  7  c.c.  decinormal  soda 
solution.  .  •  .  Total  acidity  of  10  c.c.  contents  =  7  X  0  00365 
gramme  =  0-02555  gramme  HQ  =  per  mille  X  002555 
=  2  55  grammes. 
B.  Ten  cubic  centimetres  contents  with  Congo  red  paper  fail  to 
give  change  of  color  at  4-7  c.c.  decinormal  NaOH.  .  •  .  1-71  grammes 
per  mille  HC1  =  preliminary  record  total  free  acids  plus  acid  salts. 
Same  10  c.c.  contents  give  purple  color  with  alizarin  on  addition  of 
4-9  c.c.  NaOH  solution.  .  •  .  Total  acidity  due  to  free  acids  plus  acid 
salts  in  10  c.c.  =  4-9  X  '00365  —  178  grammes  per  mille  (final 
record). 
C.  Total  combined  acid  =  A  —  B,  that  is,  2-55  —  178  =  077 
per  mille. 
45  The  qualitative  tests  for  lactic  and  butyric  acids,  etc.,  react  to  lactates  and 
butyrates,  as  well  as  the  free  acids. 
