1 6  Inorganic  Chemicals  of  the  U.S. P.      {  K  jaSfy^SK™ 
the  purity  rubric  already  commented  upon.  It  should  not  be 
considered  as  a  real  depreciation  in  quality. 
The  number  of  cases  where  the  quality  has  been  raised  by  intro- 
duction of  tests  for  impurities  not  mentioned  in  the  old  pharma- 
copoeia is  few.  Among  these  may  be  cited  a  test  for  the  presence 
of  alum  in  potassium  bitartrate,  tests  for  heavy  metals  and  arsenic  in 
potassium  hypophosphite,  and  for  barium,  chlorides,  bromides  and 
thiosulphates  in  potassium  iodide. 
The  procedure  of  most  tests  has  been  changed  but  little  ;  but 
among  the  changes  may  be  cited  the  use  of  sulphanilic  acid  and 
naphthylamine  acetate  for  detecting  nitrites  in  water,  the  detection  of 
iodine  in  calcium  bromide,  sodium  nitrate,  strontium  iodide  and 
zinc  bromide  by  shaking  out  with  chloroform  instead  of  using  starch 
paste  (the  iodine  being  in  both  cases  liberated  by  use  of  chlorine 
water),  and  the  detection  of  bromine  in  potassium  and  sodium 
bromides  by  use  of  silver  nitrate,  instead  of  by  liberation  of  the 
bromine  with  chlorine  water,  as  directed  in  the  old  pharmacopoeia. 
VOLUMETRIC  ASSAYS. 
Boric  Acid  is  now  estimated  by  titration  with  normal  solution  after 
addition  of  glycerin — an  admirably  exact  method,  though  somewhat 
costly,  since,  50  c.c.  glycerin  has  to  be  used  in  each  operation. 
Reduced  Iron  is  no  longer  titrated  with  volumetric  solution  of 
potassium  permanganate,  but  is  assayed  by  treating  it  with  a  definite 
amount  of  iodine  in  potassium  iodide  solution  and  titrating  the 
unused  iodine  with  decinormal  thiosulphate  solution. 
Magnesium  Oxide  is  assayed  by  mixing  it  with  a  definite  amount 
oi  normal  sulphuric  acid  and  titrating  the  unused  acid  with  normal 
alkali.  This  process  of  acidimetry  is  used  several  times  in  the  new 
pharmacopoeia  in  preference  to  direct  titration  with  normal  acid. 
Sodium  Sulphite  is  now  treated  with  a  definite  amount  of  decinor- 
mal iodine  solution  and  the  unused  iodine  titrated  with  decinormal 
thiosulphate  solution  until  colorless — instead  of  direct  titration  with 
decinormal  iodine  solution  and  starch  mucilage,  as  directed  in  the 
old  pharmacopoeia. 
Strontium  Iodide,  Zinc  Iodide  and  Syrup  of  Hydriodic  Acid  are  no 
longer  titrated  with  decinormal  silver  nitrate  solution  in  the  presence 
of  potassium  bichromate,  but  are  treated  with  a  definite  quantity  of 
decinormal  silver  nitrate  solution,  and  the  excess  of  silver  nitrate 
