300 
Impurity  in  Distilled  Wate7\ 
Am.  Jour.  I'liarm. 
June,  1885. 
that  which  results  from  the  use  of  strong  oxygenated  solutions  acting 
at  ordinary  pressures.  If  this  were  so,  the  decomposition  would  give 
rise  among  other  products  to  a  fatty  acid  of  the  acetic  series. 
In  offering  this  note  for  publication  I  desire  it  to  be  understood  that 
its  one  object  is  to  supply  an  explanation — hitherto  I  believe  unknown 
— of  an  important  fact,  and  to  caution  makers  of  aerated  beverages 
against  the  use  of  an  acid  impregnated  with  the  oxides  of  nitrogen. — 
Phar.  Jour,  and  Trans.,  March  (,  1885,  p.  731. 
AX  IMPUEITY  IX  DISTILLED  AYATER.^ 
By  T.  p.  Blunt,  F.  C.  S. 
In  the  late  autumn  of  last  year  an  anomaly  was  observed  in  the 
indications  of  Tidy's  permanganate  test  for  water.  It  was  found  that 
the  amount  of  iodine  set  free  from  potassium  iodide  in  the  blank  ex- 
periment with  distilled  water  was  very  much  in  excess  of  what  was  to 
be  expected,  and  the  amount  of  hyposulphite  solution  used  in  destroy- 
ing it  varied  in  successive  determinations  within  very  wide  limits.  It 
was  at  first  suspected  that  the  iodide  used  contained  iodate,  but  this 
did  not  prove  to  be  the  case.  Then  one  by  one  the  different  solutions 
were  made  afresh  until  all  had  been  changed.  Still  the  perplexing 
anomaly  continued;  75,  80,  even  120  measures  of  hyposulphite  solu- 
tion were  used  up  instead  of  the  calculated  54  or  56.  Thus  by  a  pro- 
cess of  exhaustive  elimination  I  jvas  driven  back  on  the  distilled  water 
as  the  source  of  the  trouble.  I  tested  it  by  adding  some  quantity  to 
acidified  starch  and  iodide  solution,  and  at  once  obtained  a  strong  blue 
coloration.  This  reaction  pointed  to  the  presence  of  nitrous  acid,  and 
though  I  was  not  in  a  position  to  apply  the  direct  metapheiiylenedi- 
amine  test  there  can  be  no  doubt  that  the  anomalous  results  observed 
were  to  be  attributed  to  that  body.  The  dilute  permanganate  for  the 
blank  experiment  is  prepared  at  the  time  by  mixing  a  measured  bulk 
of  a  stronger  solution  with  distilled  water,  and  no  doubt  the  great 
difference  in  the  quantities  of  iodine  liberated  was  due  to  accidental 
variations  of  the  time  intervening  between  the  mixture  and  the  addi 
tion  of  potassium  iodide,  the  mutually  destructive  reaction  between 
permanganate  of  potassium  and  nitrous  acid  occupying  some  little  time.  ^ 
1  Read  at  an  Evening  Meeting  of  the  "  Pharmaceutical  Society  "  of  Great  » 
Britain,  April  1,  1885. 
r 
