212 
Current  Literature. 
/Am.  Jour.  Pharm. 
v     March,  19 18. 
serve  as  a  sensitive  reagent  for  hydrogen  ions.  The  quantity  of 
iodine  separated  out  can  be  determined  with  sodium  thiosulphate. 
To  10  Cc.  of  filtered  gastric  juice  are  added  5  Cc.  of  a  5  per  cent, 
solution  of  potassium  or  sodium  iodate,  and  then  a  crystal  of  potas- 
sium iodide  or  sodium  iodide.  Iodine  separates  out  at  once,  as  is 
evident  from  the  dark  coloration.  Then  10  Cc.  of  tenth-normal 
solution  of  sodium  thiosulphate  are  added,  or  more,  with  a  pipet, 
until  the  fluid  is  decolored,  growing  limpid  again.  Then  a  little 
starch  solution  is  added,  and  titrated  with  a  tenth-normal  solution 
of  iodine  until  a  dark  blue  color  appears. 
The  quantity  of  iodine  which  was  released  at  first  must  be  equal 
to  the  10  Cc.  minus  the  number  of  cubic  centimeters  of  thiosulphate 
solution.  The  presence  of  acid  phosphates  and  organic  acids  does 
not  interfere  with  the  reaction,  as  they  do  not  act  unless  in  concen- 
trations above  what  are  encountered  in  the  gastric  juice.  The  iodine 
test  here  described  indicates  only  the  amount  of  free  hydrochloric 
acid;  the  bound  acid  does  not  seem  to  share  in  the  reaction.  By 
adding  merely  a  solution  of  some  iodate  and  a  little  potassium  iodide 
or  sorium  iodide  to  gastric  juice,  if  iodine  separates  out,  we  can  be 
confident  that  there  is  free  hydrochloric  acid  present.  (Reprinted 
from  The  Journal  of  the  American  Medical  Association.) 
The  Crystalline  Compound  Containing  Iodine  Which  Oc- 
curs in  the  Thyroid. — E.  C.  Kendal  has  isolated  a  compound  in 
crystalline  form  which  contains  60  per  cent,  of  iodine;  its  molecular 
weight  is  586.  Its  constitution  is  not  known,  but  it  is  neither  diiodo- 
tyrosine,  tetraiodohistidine,  triiodoimidazol,  iodized  tryptophan  nor 
iodized  phenylalanine.  In  physiological  action  it  is  identical  with 
thyroid  tissue.    {Endocrinology,  1,  153  (1917).    C.  A.,  11,  3314.) 
Microchemical  Reaction  for  Perchlorates. — The  reagents 
employed  are  (1)  a  1  :  100  aqueous  solution  of  strychnine  sulphate; 
(2)  a  1  :  50  solution  of  brucine  in  1  per  cent,  acetic  acid;  and  (3)  a 
1  : 50  aqueous  solution  suspected  to  contain  perchlorate,  which 
should  be  present  as  an  alkali  salt,  is  placed  on  a  glass  microslide 
so  that  it  forms  a  deep  convex  spheroid  and  is  not  spread  out  over 
the  surface.  Into  this  is  plunged  the  point  of  a  finely  drawn  out- 
glass  stirrer,  previously  dipped  in  either  of  the  above  alkaloidal 
solutions.  If  a  turbidity  occurs  almost  at  once,  which  happens  when 
a  moderate  quantity  of  a  perchlorate  is  present,  the  stirrer  is  with- 
