AJanSyPl898rm•}     Analysis  of  the  Gastric  Contents.  35 
Thus,  of  two  cases,  both  containing  free  acid,  one  may  contain  only 
enough  acid  to  give  a  small  amount  of  free  acid,  the  other  enough 
to  give  a  large  amount.  The  second  condition  is,  within  certain 
limits,  indicative  of  a  more  vigorous  function  and  greater  reserve 
force. 
In  cases  where  no  free  hydrochloric  acid  is  present,  a  quantitative 
estimation  is  our  only  method  of  determining  how  great  a  degree 
of  hyposecretion  is  present. 
For  satisfactory  work,  therefore,  both  a  qualitative  test  for  free 
hydrochloric  acid  and  a  quantitative  estimation  of  the  total  hydro- 
chloric acid  are  necessary. 
For  the  determination  of  the  presence  of  free  hydrochloric  acid 
there  are  four  good'  tests  suited  to  practical  work  ;  these  are  Gunz- 
burg's  phloroglucin-vanillin  test,  Boas's  resorcin  test,  Tbpfer's  di- 
methyl-amido-azo-benzol  test,  and  the  00  Tropeolin  test. 
Gunzburg's  reagent  consists  of  phloroglucin  2,  vanillin  1,  abso- 
lute alcohol  30.33  One  drop  of  the  contents  is  heated  on  a  white 
dish  over  a  water-bath,  and  one  drop  of  the  reagent  added.  If  free 
hydrochloric  acid  be  present,  a  red  zone  of  crystals  is  formed. 
Boas's  reagent  consists  of  resorcin  5,  sacch.  alb.,  3,  spiritus 
dil.  ad.,  100.  The  test  is  performed  in  a  manner  similar  to  that 
described  for  the  Gunzburg.  Free  hydrochloric  acid  gives  a  purple- 
red  color.34  These  two  reagents,  the  Boas  and  the  Gunzburg,  give 
no  reaction  whatsoever  with  organic  acids,  and  are  not  interfered 
with  by  peptones  or  acid  salts. 
The  00  Tropeolin  test  consists  of  the  addition  of  one  drop  of  a 
saturated  alcoholic  solution  of  00  tropeolin  to  one  drop  of  the  con- 
tents over  a  water-bath.  Free  hydrochloric  acid  gives  a  deep  bluish- 
purple  color.  Organic  acids  give  an  orange  color ;  acid  salts  a 
tawny  yellow. 
Tbpfer's  reagent  consists  of  y2  per  cent,  alcoholic  solution  of  di- 
methyl-amido-azo-benzol.  One  drop  of  this  reagent  is  added  to  a 
portion  of  the  contents  in  a  test-tube.  If  free  hydrochloric  acid  be 
present  a  carmine-red  color  appears.  This  reagent  gives  a  brown- 
ish-red color  with  organic  acids.35 
All  four  tests  are  of  about  equal  delicacy  in  testing  straight  solu- 
33  Centralblatt f.  klin.  Med.,  No.  40,  1887. 
34  Boas  :  Diagnostik,  2d  Auflage,  1891,  s.  134. 
35 
Topfer  :  Zeitsch.  f.  Physiolog.  Chemie,  1894,  Bd.  XIX,  H.  1,  s.  104. 
