AmMay!'Sarm"}      Estimation  of  Hydrochloric  Acid.  251 
manganate,  manganic  peroxide,  and  oxygen  ;  the  resulting  potassic 
manganate  is  acted  on  by  chlorine  generated  by  the  action  of  the  per- 
oxide on  some  fresh  chlorate,  forming  potassic  chloride,  manganic  per- 
oxide, and  oxygen,  so  that  the  peroxide  is  being  continually  repro- 
duced. The  quantity  of  chlorine  evolved  corresponds  to  only  a  very 
small  proportion  of  the  manganic  peroxide  present,  so  if  the  first  action 
really  takes  place  the  chlorine  must  be  absorbed  and  employed  in  con- 
verting the  potassium  into  chloride. 
Discussion. — Professor  Thorpe,  referring  to  the  well-known  fact 
that  no  perchlorate  is  formed  in  presence  of  manganese  dioxide,  asked 
how  this  was  to  be  explained. 
Mr.  Williams  stated  that  he  had  been  unable  to  obtain  the  theoret- 
ical amount  of  oxygen  from  potassium  chlorate  by  heating  it  in  vacuo; 
a  gas  was  given  off  which  attacked  mercury — presumably  chlorine, 
and  therefore  it  was  probable  that  the  residue  contained  potassium 
peroxide.  On  heating  silver  iodate  in  vacuo  the  theoretical  amount 
of  oxygen  was  obtained  without  difficulty. 
Professor  McLeod  said  that  he  was  unable  to  account  for  the  non- 
production  of  perchlorate  in  presence  of  manganese  dioxide  ;  as  potas- 
sium perchlorate  was  not  decomposed  by  heating  with  manganese  diox- 
ide, it  probably  was  not  even  an  ephemeral  product.  He  had  without 
difficulty  obtained  almost  the  theoretical  amount  of  oxygen  from  chlo- 
rate. He  did  not  think  that  the  pink  color  was  due  to  ferrate  as  had 
been  suggested,  as  he  had  found  that  iron  oxide  gave  a  somewhat 
different  color. 
Professor  Ramsay  remarked  that  Stas,  in  his  determination  of  the 
ratio  of  potassium  chloride  to  oxygen  in  chlorate,  had  not  found  that 
peroxide  was  formed. 
ESTIMATION  OF  FREE  HYDROCHLORIC  ACID  IN  THE 
CONTENTS  OF  THE  STOMACH.1 
By  J.  Sjoqvist. 
The  oldest  method  is  that  of  Bidder  and  Schmidt,  who  were  the 
first  to  prove  the  existence  of  free  hydrochloric  acid  in  the  gastric 
juice.  Rabuteau's  method,  modified  by  Cahn  and  v.  Mering  (Deut. 
Arch.  Hin.  Med.,  xxxix,  239),  consists  in  distilling  off  the  volatile  acids 
and  shaking  the  residue  with  a  large  excess  of  ether  which  takes  up 
1Zeit.  physiol.  Chem.,  xii.,  1-11  ;  reprinted  from  Jour.  Chem.  Soc,  March, 
1889. 
