Am.  Jour.  Pharm. ) 
June,  1883.  j 
Lithice  Citras. 
319 
silver  vessel,  treated  with  ammonia  and  ammonium  carbonate  and  the 
resulting  lithium  carbonate  washed  to  free  it  from  chlorides. 
2.  Frost^s  method  for  obtaining  lithium  carbonate  from  lepidolite. — 
Fuse  together  lepidolite,  well  powdered,  10  parts ;  barium  carborate, 
10  parts ;  barium  sulphate,  5  parts  ;  potassium  sulphate,  3  parts.  The 
heavy  silicate  and  sulphate  of  barium  sink  to  the  bottom,  whilst  a 
layer  of  sulphates  of  potassium  and  lithium  floats  on  the  surface  of 
the  fused  mass.  These  are  then  extracted  by  lixiviation,  and  the  sul- 
phates are  converted  into  chlorides  by  precipitation  with  chloride  of 
l)arium.  The  liquid  is  evaporated  to  dryness  and  the  potassium  and 
lithium  chlorides  are  separated  by  treatment  with  a  mixture  of  absolute 
alcohol  and  ether,  which  dissolves  the  lithium  and  leaves  the  potas- 
sium. Ammonia  and  ammonium  carbonate  are  then  added  and  the 
carbonate  of  lithium  is  collected  and  well  washed.  It  will  be  seen 
that  the  impurities,  i.  e.,  the  calcium,  potassium  and  sodium  chlorides, 
are  very  difficult  to  separate  entirely  from  the  lithium,  owing  to  the 
partial  solubility  of  potassium  and  sodium  chloride  in  alcohol. 
Both  the  B.  P.  and  the  U.  S.  P.  recommend,  as  a  means  for  the 
quantitative  estimation  of  the  citrate,  incineration,  at  a  red  heat,  and 
weighing  the  residue  as  carbonate,  when|53  per  cent.  (52'8  per  cent.) 
should  be  obtained. 
This  method  is  useless  as  a  means  of  estimation  of  the  amount  of 
lithium  present,  for  the  carbon  cannot  be  entirely  got  rid  of  without 
very  prolonged  heating,  by  which  means  the  carbonate  becomes  caustic ; 
the  resulting  greyish-white  mass  is  very  deliquescent,  thus  introducing 
another  source  of  error. 
An  improvement  on  this  method  is  given  in  the  "  U.  S.  Dispensatory," 
where  it  is  directed  to  incinerate  and  treat  the  mass  with  sulphuric 
acid,  and  weigh  the  resulting  sulphate  of  lithium.  100  grains  citrate 
should  yield  22-3  (78*57,  Edit.  ''Am.  Jour.  Phar.")  grains  of  sulphate. 
In  making  an  analysis  of  lithium  citrate,  the  probable  impurities 
and  adulterations  to  look  for  are  powdered  petalite  or  lepidolite,  salts 
of  calcium,  potassium  and  sodium. 
First  as  regards  powdered  petalite  or  lepidolite.  Take  a  weighed 
quantity  (1  to  2  grams),  and  treat  with  boiling  water ;  if  any  of  the 
-powder  remains  insoluble,  this  must  be  collected,  washed,  incinerated, 
and  weighed.  For  calcium  : — Take  about  5  grams,  dissolve  in  water, 
add  ammonium  oxalate,  collect,  wash,  incinerate,  and  weigh  as  CaCOg. 
The  real  difficulty  is  when  it  comes  to  the  estimation  of  the  potas- 
