'^'"■jlri8^75.^'"'  }  Laboratory  Notes, 
LABORATORY  NOTES. 
BY  J.  LAWRENCE  SMITH,  OF  LOUISVILLE,  KY. 
From  long  experience  I  have  found  it  vain  to  rely  upon  manufac- 
turers of  chemicals  for  reagents  of  that  exceeding  purity  w^hich  all 
analytical  chemists  often  require  for  conducting  their  researches,  and  it 
has  been  my  habit,  through  a  long  experience  in  analytical  chemistry, 
to  prepare  with  my  own  hands  certain  of  the  chemicals  used  by  me 
and,  while  many  of  the  processes  of  preparing  them  embrace  nothing 
specially  novel,  still  my  experience  in  making  them  has  been  of  certain 
importance  to  others,  and  from  time  to  time  I  will  take  opportunities 
to  give  more  general  information  of  these  methods,  which  may  possibly 
be  of  service  to  some,  especially  as,  while  seeking  first  for  purity,  I  have 
been  obliged  to  economize  time  by  the  least  amount  of  manipulation. 
Pure  Carbonate  of  Soda. — For  many  years  all  the  carbonate  of  soda 
used  by  me  in  mineral  analysis  has  been  prepared  in  the  following 
method,  viz.,  by  making  oxalate  of  soda  and  then  decomposing  it  by 
heat.  It  can  be  described  in  the  shortest  possible  manner  by  giving  the 
figures  and  method  employed  for  obtaining  a  given  result.  The  car- 
bonate of  soda  commonly  used  has  been  the  crystals  of  ordinary  sal 
soda,  washed  with  a  little  water  to  detach  the  adhering  dust,  or  if  one 
has  pure  soda  at  his  command,  it  can  be  used  to  advantage.  The  oxalic 
acid  used  is  the  ordinary  oxalic  acid  of  the  shops  once  recrystallized,  of 
which  crystallized  acid  I  always  have  a  supply  of  several  pounds  in  my 
laboratory. 
63  grammes  of  oxalic  acid  and  143  grammes  of  sal  soda  are  dissolved 
by  heat  in  200  c.c.m.  of  distilled  water — filter  the  solution  if  necessary 
— to  the  solution  of  soda,  when  cold,  add  the  solution  of  oxalic  acid, 
just  hot  enough  to  keep  from  crystallizing  ;  add  it  bv  degrees,  stirring 
well ;  after  the  mixture  is  completed,  it  is  expected  that  the  solution 
will  have  an  alkaline  reaction,  to  keep  any  trac^  of  soda  in  solution  ; 
the  oxalate  of  soda  will  be  precipitated  in  great  part  shortly  after  the 
operation  is  completed  ;  let  stand  for  a  short  while  to  cool  completely, 
decant  the  supernatant  liquid,  add  a  little  distilled  water,  break  up  with 
a  stirrer  the  lumps  of  crystals  that  may  have  formed,  throw  on  a  filter 
over  a  Bunsen  aspirator,  using  a  six-inch  filter,  wash  with  about  a  half 
litre  of  distilled  water,  and  let  dry.  This  may  be  placed  aside  in  a  glass 
bottle  if  not  needed  at  once  for  forming  carbonate  of  soda  ;  the  quan- 
