Am.  Jonr.  Pharm  ) 
Juue,  1883.  J 
Lithice  Citras. 
317 
acid,  and  evaporating  the  filtered  residue  to  dryness,  1  part  of  the 
residue  should  be  completely  soluble  in  3  parts  of  absolute  alcohol, 
which  when  ignited,  should  burn  with  a  crimson  flame,  and  the  addi- 
tion of  an  equal  volume  of  stronger  ether  to  the  alcoholic  solution 
should  produce  no  precipitate  (salts  of  alkalies  absent).  On  dissolv- 
ing another  portion  of  the  residue  in  a  small  quantity  of  water,  the 
solution  should  produce  no  precipitate  with  the  test  solution  of  ammo- 
nium oxalate  (salts  of  alkaline  earths).  The  aqueous  solutiofi  should 
remain  unaffected  by  sulphuretted  hydrogen  or  ammonium  sulphide 
(absence  of  metals)." 
Lithium  citrate,  as  Squire  remarks,  is  not  deliquescent.  It  appears 
in  commerce  either  as  a  crystalline  or  pulverulent  substance.  When 
crystalline  its  composition  is  exceedingly  uniform;  when  in  powder  its 
composition  is  rather  apt  to  vary,  and  does  not  resemble  the  citrate  of 
lithium  of  the  B.  P.,  which  is  anhydrous;  whereas  Mr.  Umney  found 
in  an  examination  of  some  ten  different  samples,  in  no  case  more  than 
84  per  cent.,  while  most  were  about  74  per  cent,  of  anhydrous  salt. 
Mr.  Umney  dried  the  specimens  examined  first  at  100°  C,  and  then 
finished  at  115°  C,  or  so  as  to  produce  the  official  article;  the  differ- 
ence between  the  two  dryings  is  about^  5  per  cent.,  corres}jonding  to 
about  1  molecule  of  water,  so  that,  if  the  formula  Li3CgFl30y.4H20 
be  accepted,  then  tlie  salt  dried  at  100°  will  lose  3  of  these  4  mole- 
cules of  water.  This  was  the  composition  of  some  crystals  of  pure 
lithium  citrate,  made  by  Mr.  Sandford  and  presented  to  Mr.  Umney,, 
which  contained  about  73  per  cent,  anhydrous  citrate. 
Out  of  four  samples  examined  by  me,  one  contained  86  per  cent., 
another  83*5  per  cent.,  and  the  other  two  75*2  per  cent,  of  anhydrous 
citrate  of  lithium. 
But  not  only  does  the  commercial  article  contain  water  of  crystalli- 
zation, but  other  substances,  distinct  impurities,^  the  most  common  of 
which  are  calcium,  magnesium,  potassium  and  sodium,  and  sometimes 
traces  of  the  heavier  metals.  Occasionally  the  citrate  is  found  adul- 
terated with  powdered  petalite,  bitartrate  of  potassium,  etc.  Before 
proceeding  to  discuss  the  methods  of  detecting  and  estimating  these 
impurities,  it  will  be  as  well  to  see  how  they  get  into  the  citrate. 
^  Since  writing  the  above  Mr.  Umney  has  found  that  this  varies  consid- 
erably. 
2  Mr.  W.  L.  Scott,  out  of  twenty-seven  samples  of  lithium  salts,  found 
sixteen  pure,  six  fair,  and  five  adulterated  with  Na2C03,KHC4H406,  pow- 
dered petalite,  etc.,  etc.    ("  Year-Book  of  Pharmacy,"  1870,  p.  452). 
