VALUATION  OF  CHLORIDE  OF  LIME  BY  SULPHATE  OF  IRON.  359 
the  small  quantity  of  sugar  present.  If  iodate,  however,  be 
present,  the  precipitate  becomes  red  almost  immediately.  The 
samples  under  examination  are  set  aside,  oxidation  proceeds,  and 
the  precipitates  subside ;  the  relative  quantity  of  each  is  noticed 
and  registered  accordingly.  If,  in  the  use  of  this  test,  iodate  is 
suspected,  it  may  be  subsequently  shown  more  distinctly  by  means 
of  the  usual  test  of  hydrochloric  acid. 
To  establish  the  trustworthiness  and  value  of  the  test  now  pro- 
posed, some  iodide  of  potassium  was  prepared  as  pure  as  possible ; 
to  a  solution  of  this  a  drop  of  the  test  was  added — no  change 
occurred,  nor  was  there  any  indication  of  a  precipitate  after 
standing  twenty-four  hours.  One  drop  of  a  solution,  containing 
one  grain  of  carbonate  of  potash  dissolved  in  a  thousand  grains 
of  distilled  water,  was  now  added,  and  a  pale  blue  precipitate 
ensued.  A  second  specimen  was  prepared,  containing  both  car- 
bonate and  iodate  of  potash ;  on  adding  the  test  first  a  deeper 
and  then  a  red  precipitate  was  formed.  A  third,  containing 
iodate  only,  was  now  made — the  test  being  added,  a  red  precipi- 
tate formed  immediately. — Pharmaceutical  Journal,  May,  1856. 
VALUATION  OF  CHLORIDE  OF  LIME  BY  MEANS  OF  SULPHATE 
OF  IRON. 
Wittstein  and  Claude  have  made  some  comparative  experi- 
ments on  the  valuation  of  bleaching  powder,  and  have  come  to 
the  conclusion  that  the  reaction  with  sulphate  of  iron  is  not  capa- 
ble of  affording  accurate  results.  The  reaction  is  supposed 
to  be — 
(1.)  CaO-f  010  and  4  (FeO+  S03)  =  CaCl  and  2  (Fe,03  +  2  SO,, 
However,  in  making  the  experiment,  there  is  always  an  evolu- 
tion of  chlorine,  even  before  the  whole  of  the  protoxide  of  iron 
is  converted  into  peroxide.  Moreover,  by  comparing  the  results 
obtained  by  the  valuation  with  sulphate  of  iron  and  those  ob- 
tained with  arsenious  acid,  the  latter  always  gives  higher  per- 
centage. 
The  evolution  of  chlorine  is  owing  to  the  reaction  being  of  the 
following  nature : — 
(2.)  CaO+C10+  2  (FeO+S03)=Ca  0+S03+Fe203S03+Cl. 
