1 74  Potassium  Nitrite  in  Potassium  Hydrate.     { AmApr^-  f^6arm* 
the  acidified  solution  with  potassium  permanganate.  In  the  specimen  it 
was  found  to  amount  to  1  per  cent.  This  quantity,  although  small,  is 
of  medical  and  pharmaceutical  importance  on  account  of  the  powerful 
therapeutic  action  of  the  alkaline  nitrites.  Other  commercial  speci- 
mens were  then  examined,  and  in  all  cases  appreciable  quantities  of 
potassium  nitrite  were  detected  and  estimated  with  the  following 
result : 
Specimen  A  contained  1*0  per  cent,  of  KN02 
B      "         074  " 
"       C      "         0-56   "  " 
D      "         0-47   "  " 
"       E      "         0-34   "  " 
The  specimens  also  contained  nitrate,  about  4*5  per  cent,  of  chloride, 
silica  and  alumina ;  they  contained  on  an  average  78-79  per  cent,  of 
total  alkali. 
Without  knowledge  of  the  previous  history  of  these  specimens,  it 
is  impossible  to  make  any  definite  statement  about  the  origin  of  the 
potassium  nitrite.  It  might  result  from  the  deoxidation  of  the  nitrate 
by  heat,  or  possibly  from  the  oxidizing  action  of  fused  potash  on  an 
organic  compound  containing  nitrogen. 
It  is  important  that  the  potassium  hydrate  and  the  salts  prepared 
therefrom  for  medicinal  purposes  should  be  free  from  nitrite,  and  I 
therefore  mention  that  which  I  have  found  to  be  the  most  ready 
method  of  applying  the  potassium  iodide  reaction  for  its  detection. 
Working  on  the  usual  lines,  the  solution  and  acidification  of  the  sub- 
stance cause  the  evolution  of  much  heat,  and  unless  special  precautions 
are  taken  loss  of  nitrous  acid  occurs.  The  best  method  consists  in 
adding  a  little  solution  of  potassium  iodide  to  about  an  ounce  of  diluted 
sulphuric  acid,  preferably  contained  in  a  flask.  To  this  about  half  a 
stick  (5  grams)  of  potash  should  be  added,  and  the  flask  rapidly  ro- 
tated, when  iodine  will  be  liberated,  and  color  the  liquid  from  a  yel- 
low to  a  reddish-brown,  depending  on  the  quantity  of  nitrite  present. 
The  estimation  of  the  nitrite  is  most  conveniently  conducted  with 
about  the  same  quantity  of  potash  dissolved  in  water  and  acidified 
without  rise  of  temperature  with  pure  diluted  sulphuric  acid.  Fur- 
ther, it  should  be  added  that  since  potassium  nitrite  is  insoluble  in  al- 
cohol the  potassium  hydrate  which  is  purified  by  solution  in  alcohol 
and  known  in  commerce  as  "  potash  by  alcohol "  is  free  from  this  im- 
purity.— Phar.  Jour,  and  Trans.,  March  13.  1886,  p.  778. 
