A™;nuaryri906m'}      Inorganic  Chemistry  of  the  U.S. P.  25 
solution  be  diluted  with  previously  boiled  distilled  water  to  measure 
IOO  c.c.  and  13-6  c.c.  of  this  solution  be  added  to  35  c.c.  of  tenth- 
normal oxalic  acid  V.  S.,  contained  in  a  graduated  cylinder,  and, 
after  thoroughly  shaking,  the  mixture  be  diluted  with  distilled  water 
to  measure  50  c.c.  Then  after  shaking  again  and  the  precipitate  has 
settled,  10  c.c.  of  the  clear  solution,  after  diluting  with  about  50  c.c. 
of  water  and  adding  5  c.c.  of  sulphuric  acid,  should  require  not  more 
than  2  c.c*.  of  tenth-normal  potassium  permanganate  V.  S.  to  pro- 
duce a  permanent  pink  tint.  This  method  is  that  of  Hempel,  and 
depends  upon  precipitating  the  lead  as  oxalate,  using  a  measured 
excess  of  standard  oxalic  acid  solution.  Then  after  acidulating  with 
sulphuric  acid,  titrating  for  the  excess  of  oxalic  acid  with  standard 
permanganate  solution.  By  deducting  the  quantity  of  tenth-normal 
permanganate  solution  required  from  the  quantity  of  tenth-normal 
oxalic  acid  V.  S.  taken,  the  quantity  of  the  latter,  which  reacted 
with  the  lead,  is  obtained,  and  by  a  calculation  the  weight  of  lead 
subacetate  present  is  found. 
The  reactions  involved  are  illustrated  by  the  equations  : 
(1)  Ph20  (C2H309)  +  2H2C204,  2H20  =  2PbC204  4-  2HC2H302 
3H20. 
(2)  5H2C204  +  3H2S04  +  2KMn04  =  K2S04  +  2MnS04  + 
ioC02  +  8H20. 
Liquor  Potassii  Arsenitis  is  assayed  as  before,  except  that  the  solu- 
tion instead  of  being  boiled  with  the  sodium  bicarbonate  is  slightly 
acidified  with  diluted  hydrochloric  acid  and  then  made  alkaline  with 
sodium  bicarbonate  before  titrating  with  the  standard  iodine  V.  S. 
Starch  is  not  employed  as  indicator. 
Lithium  Salts. — Definite  standards  of  purity  are  given  in  each 
case,  as  well  as  sufficient  and  satisfactory  tests  for  the  detection  of 
possible  impurities. 
The  benzoate  and  salicylate  are  assayed  by  igniting  in  a  porcelain 
crucible,  together  with  some  powdered  anhydrous  ammonium  sul- 
phate and  the  residue  weighed.  These  salts  were  formerly  ignited 
and  the  residue,  consisting  of  lithium  carbonate  and  carbon,  dis- 
solved in  water  and  titrated  with  normal  sulphuric  acid  V.  S.  The 
results  by  this  volumetric  method  were  usually  a  little  too  low. 
The  new  method  may  prove  more  satisfactory.  The  same  volu- 
metric method  was  formerly  also  employed  in  the  assay  of  the 
