28  Inorganic  Chemistry  of  the  U.S. P.      {Ajairy fit- 
test ;  and,  strange  to  say,  tests  for  chlorides,  sulphates  and  for  sodium 
are  omitted  in  nearly  every  instance.  The  other  tests  for  impurities 
remain  about  the  same  as  before. 
Potassium  hypophosphite  is  headed  with  a  precaution  notice 
against  triturating  or  heating  the  salt  with  nitrates,  chlorates  or 
other  oxidizing  agents. 
Potassii  citras  effervescence  is  differently  prepared  than  formerly. 
See  the  Pharmacopoeia. 
Sodium  Salts. — Very  few  changes  are  noted  in  the  sodium  salts, 
aside  from  those  spoken  of  earlier  in  this  review.  Definite  stand- 
ards of  purity  are  assigned  in  the  case  of  each  salt.  The  assay 
processes  given  are  mostly  the  same  as  before;  the  exceptions  being 
sodium  hypophosphite,  in  which  the  assay  is  omitted;  sodium 
sulphite,  sodium  bisulphite,  and  sodium  nitrite  described  below. 
As  regards  the  tests  for  impurities  no  remarkable  changes  are 
noticed,  except  that  as  in  the  potassium  salts,  the  tests  for  chloride, 
sulphate  and  calcium  are  omitted.  The  "  time-limit  test  for  heavy 
metals  "  is  employed  except  in  sodium  chlorate,  in  which  the  am- 
monium sulphide  test  is  used.  Arsenic  is  detected  by  the  "  modified 
Gutzeit's  test." 
A  new  assay  process  for  Sodii  Nitris  is  introduced  to  replace  the 
gasometric  method  of  the  old  Pharmacopoeia.  In  the  performance 
of  the  latter  method  a  nitrometer  was  required,  and  inasmuch  as 
this  instrument  is  rarely  found  in  drug  stores,  the  assay  was  seldom 
made  by  the  pharmacist.  The  new  method  is  altogether  a  volumetric 
one,  and  the  assay  can  be  accomplished  readily  and  without  the  use 
of  any  unusual  instruments.  It  depends  upon  the  reaction  between 
sodium  nitrite  and  potassium  permanganate  in  the  presence  of  sul- 
phuric acid.  The  nitrite  is  oxidized  to  nitrate  and  the  permanganate 
decomposed  as  the  equation  shows : 
5NaN02  +  2KMn04  +  3H2S04  =  5NaN03  +  K,S04  +  2MnS04  + 
3H2Q 
In  detail  the  process  is  as  follows:  Thirty  c.c.  of  tenth-normal 
potassium  permanganate  V.  S.  are  diluted  with  about  150  c.c.  of 
distilled  water.  Then  5  c.c.  of  sulphuric  acid  and  10  c.c.  of  a  solu- 
tion containing  01  gramme  of  sodium  nitrite  are  added;  the  liquid 
is  then  warmed  to  1040  F.  and  allowed  to  stand  for  five  minutes. 
It  is  then  titrated  with  tenth-normal  oxalic  acid  V.  S.  until  decolor- 
