348  Solubility  of  Carbonate  of  Lithium.      { AmjS^-^rm- 
flask  containing  a  solution  be  heated  in  a  water-bath,  at  about  50°  C, 
evolution  of  gas  begins  and  separation  of  lithium  carbonate.  The 
solution  shows  itself  more  resistent  to  the  introduction  of  atmospheric 
air;  it  requires  a  strong  current  to  be  passed  through  it  for  a  con- 
siderable time  before  the  lithium  carbonate  commences  to  separate. 
Although  a  freshly  prepared  and  filtered  solution  of  bicarbonate  of 
lithium  gave,  in  a  quantitative  determination  of  the  carbonic  acid,  an 
amount  which  fell  only  slightly  below  the  quantity  calculated  for 
LiHC03,  an  older,  freshly-filtered  solution,  from  which  lithium  car- 
bonate had  already  separated,  never  gave  the  amount  of  carbonic 
acid  required  for  that  formula.  The  carbonic  acid  found,  which 
agreed  closely  in  several  experiments,  indicated  such  a  quantity  of 
simple  carbonate  as  corresponded  closely  to  the  proportional  solu- 
bility of  the  latter. 
I.  A  freshly  prepared  (filtered)  solution,  containing  in  100  parts 
12-63  parts  of  LiHCOs,  yielded  7'95  of  C02;  calculated,  8-17. 
II.  An  old  (filtered)  solution,  containing  in  100  parts  8*53  parts 
of  LiHCOs,  yielded  4-87  of  C02;  calculated,  5.52. 
A  freshly  prepared  solution  of  bicarbonate  of  lithium  gives  with 
mercuric  chloride  solution  a  strong  white  turbidity,  which  remains 
unaltered  for  a  minute;  whilst  in  a  (freshly  filtered)  solution  from 
which  lithium  carbonate  has  already  separated,  the  turbidity  caused 
by  the  addition  of  mercuric  chloride  is  not  pure  white  at  first,  and, 
after  a  few  seconds,  passes  into  a  red  precipitate. 
From  a  solution  of  bicarbonate  of  lithium  it  is  always  the  mono- 
carbonate  that  crystallizes  out,  and  I  have  not  succeeded  in  separating 
bicarbonate  or  a  sesquicarbonate.  I  think  it  necessary,  considering 
the  numerous  erroneous  statements  to  emphasize  this.  In  very  slow 
evaporation  (in  an  exsiccator  or  standing  in  the  air)  a  dense  verrucose 
crystalline  crust  forms  on  the  surface  of  the  liquid,  which,  under  the 
microscope,  is  seen  to  consist  of  groups  of  small,  irregular  crystals, 
that  decrepitate  when  heated.  In  a  rapid  evaporation  upon  a  water- 
bath  there  is  formed,  on  the  contrary,  partially,  a  crystalline  powder, 
refracting  light  strongly,  which,  under  the  microscope,  is  seen  to 
consist  of  well-formed  prismatic  crystals,  that  do  not  decrepitate 
when  heated.  Upon  covering  a  concentrated  solution  of  lithium 
bicarbonate  with  a  layer  of  alcohol  there  was  at  once  a  lively  evolu- 
tion of  carbonic  acid  and  amorphous  lithium  carbonate  was  thrown 
down. 
