DECOMPOSITION  OF  IODIDE  OF  STARCH,  ETC. 
261 
C40  H20  0,3  +  4  HO  =  C14  H6  0,  +  G14  HG  0,  +  Cia  HI2  012 
Benzohelicin       Benzoic  acid        Hydruret  of    Grape  sugar 
Salicyle 
Benzohelicin  may  be  converted  into  helicin  by  boiling  with  a 
base  that  abstracts  benzoic  acid  without  acting  upon  helicin. — 
Pharm.  Jour,  and  Tram.  Feb.  1,  1856. 
ON  THE    DECOMPOSITION"  OF  IODIDE   OF   STARCH    BY  THE 
ANIMAL  FLUIDS. 
By  John  C.  Dalton,  Jr.,  M.  D. 
1'rofrssor  of  Physiology  in  the  College  of  Physicians  and  Surgeons,  New  York. 
Some  months  since,  while  experimenting  on  the  digestion  of 
starch,  and  its  conversion  into  sugar  in  the  intestine,  I  observed 
that  the  iodide  of  starch  became  very  rapidly  decolorized  on 
being  digested,  at  the  temperature  of  100°  F.,  with  the  intesti- 
nal fluids  taken  from  the  duodenum  of  a  recently  killed  dog.  It 
appeared,  also,  that  this  effect  was  produced  some  time  before 
any  sugar  had  made  its  appearance  in  the  mixture,  and  would 
even  take  place,  with  nearly  equal  promptness,  at  the  ordinary 
temperature  of  the  air.  It  seemed,  at  first,  probable,  that  the 
decolorization  was  owing  to  a  partial  alteration  of  the  starch, 
which  passed  into  an  intermediate  condition,  before  undergoing 
its  final  conversion  into  sugar.  Subsequent  examination,  how- 
ever, showed  that  it  was  due  to  a  simple  decomposition  of  the 
iodide  of  starch  by  the  organic  substances  of  the  intestinal  fluids. 
Nearly  all  the  animal  fluids,  indeed,  when  in  a  fresh  condition, 
not  only  decolorize,  more  or  less  promptly,  the  blue  iodide  of 
starch,  but  prevent  entirely  the  usual  reaction  between  starch 
and  iodine,  when  this  latter  substance  is  present  in  small  quan- 
tity. AYhen  the  iodide  of  starch,  ready  formed,  comes  in  con- 
tact with  these  fluids,  the  iodine  leaves  the  starch  and  combines 
with  the  organic  matters;  and  it  is  under  the  form  of  such  an 
organic  combination  that  the  iodine  is  absorbed  from  the  intes- 
tine, passes  through  the  circulation,  and  is  discharged  by  the 
urine.  The  precaution,  therefore,  which  is  sometimes  inculca- 
ted, in  the  administration  of  free  iodine,  to  give  the  medicine  in 
the  interval  between  two  meals,  lest  it  should  combine  with  the 
starchy  matters  of  the  food,  and  become  insoluble  and  inert,  is 
