58  Lithium  Benzoate  and  Salicylate.  {AFebr7^mm' 
only  one  sample  of  lithium  benzoate  made  with  this  acid.  The 
ex-toluol  acid  may  contain  chlorinated  compounds,  and  the  urine- 
acid  is  liable  to  be  contaminated  with  hippuric  acid  and  possess  a 
urine-like  odor. 
The  samples  of  lithium  benzoate  examined  represent  the  best 
goods  available  in  this  country.  The  results  are  tabulated  on  the 
next  page. 
Only  those  pharmacopoeial  requirements  will  be  enumerated  here 
on  which  it  is  necessary  or  seems  desirable  to  make  comment,  as 
the  result  of  this  investigation. 
"Soluble  at  150  C.  in  4  parts  of  water,  and  in  12  parts  of  alco- 
hol; in  2-5  parts  of  boiling  water  and  in  10  parts  of  boiling  alcohol. 
Sodium  benzoate  increases  its  solubility  in  water  and  diminishes 
that  in  alcohol."  By  comparing  the  above  statements  with  the 
results  on  solubility  in  the  preceding  table,  it  would  seem  that  the 
samples  of  lithium  benzoate  were  contaminated  with  the  correspond- 
ing sodium  salt.  An  examination,  however,  showed  that  such  was 
not  the  case.  This  was  farther  supplemented  by  making  a  sample 
of  lithium  benzoate  from  lithium  carbonate  and  benzoic  acid  of 
known  purity.    No.  1  is  the  sample  so  prepared. 
There  certainly  are  marked  differences  between  the  solubilities 
as  given  by  the  U.S.P.  and  those  actually  obtained  in  this  investiga- 
tion. 
The  solubilities  at  150  C.  were  determined  by  the  digestion 
method.  The  solvent  was  allowed  to  act  for  several  days,  with  fre- 
quent agitation,  on  an  excess  of  the  chemical  at  a  temperature 
slightly  below  150  C.  When  the  solvent  did  not  appear  to  take  up 
any  more  of  the  salt,  the  temperature  was  kept  at  150  C.  for  about 
four  hours,  shaken  as  above,  then  filtered  and  the  amount  of  solvent 
determined  in  a  given  weight  of  the  filtrate. 
The  solubilities  in  " boiling  water "  and  ''boiling  alcohol"  were 
determined  by  estimating  the  amount  of  the  salt  actually  dissolved 
at  the  boiling  point  of  the  saturated  solution.  This,  of  course,  is 
much  higher  than  ioo°  C.  for  water,  or  about  780  C.  for  alcohol. 
The  writer  has  seen  the  boiling  point  of  such  an  aqueous  mixture 
rise  up  to  1400  C.  and  above,  and  an  alcoholic  solution  as  high  as 
95°  C. 
On  ignition,  a  residue  of  lithium  carbonate  mixed  with  carbon  is 
left.  It  would  be  more  nearly  correct  to  say  that  the  mixture  con- 
sists of  lithium  carbonate,  carbon  and  the  oxides  of  lithium. 
