220 
ON  FORMIC  ACID. 
decomposed.  Oxalic  acid  subjected  to  the  action  of  heat,  is 
converted  into  water,  carbonic  acid,  and  oxide  of  carbon.  The 
water  and  oxide  of  carbon  contain  the  elements  of  formic  acid, 
and  are  made  to  combine  through  the  intervention  of  glycerin, 
while  the  carbonic  acid  is  given  off.  A  quart  of  water  was  now 
added,  and  the  whole  distilled ;  another  quart  was  added,  and 
again  distilled;  the  distilled  products,  containing  the  acid  in  a 
dilute  state,  were  saturated  with  milk  of  lime,  and  evaporated  to 
dryness,  yielding  six  and  a  half  ounces  of  formiate  of  lime.  This 
was  placed  in  a  retort,  five  and  a  quarter  ounces  of  pure  sulphuric 
acid,  and  two  and  a  quarter  ounces  of  water  added,  and  the  whole 
distilled,  until  the  distillate  measured  six  fluid  ounces.  The  acid 
as  thus  obtained  had  a  suffocating  odor,  like  that  of  sulphurous 
acid,  and  had  the  sp.  grav.  1.104.  The  glycerin  used  in  the 
operation  was  merely  discolored,  and  was  used  again  in  forming 
fresh  portions  of  the  acid. 
Formic  acid  was  obtained  at  the  highest  degree  of  concentra- 
tion by  passing  dry  sulphuretted  hydrogen  over  dry  formiate  of 
lead  contained  in  a  long  glass  tube,  until  the  lead  salt -was 
entirely  decomposed.  By  applying  a  very  gentle  heat  to  the  tube, 
the  formic  acid  was  driven  into  a  small  receiver.  This  acid  was 
so  caustic  as  to  raise  a  blister  when  dropped  on  the  skin,  and  had 
the  sp.  grav.  1.125. 
I  combined  several  of  the  alkaloids  with  formic  acid.  Formi- 
ate of  strychnia  was  obtained  in  fine  silky  crystals,  quite  soluble 
in  hot  and  cold  water,  sparingly  so  in  alcohol  and  ether,  and 
gave  the  characteristic  violet  color  with  chromic  acid.  Formiate 
of  brucia  was  obtained  in  crystals  slightly  soluble  in  hot  and 
cold  water  and  alcohol,  almost  insoluble  in  ether.  According  to 
Larocque  and  Thiebierge,  the  salts  of  brucia  give  first  a  milky, 
then  a  coffee  colored,  and  finally  a  chocolate  brown  precipitate  with 
chloride  of  gold.  This  reaction  was  manifested  with  the  sulphate  ; 
but  with  the  formiate  it  gave  first  a  yellow  precipitate,  gradually 
changing  to  a  dirty  green.  With  nitric  acid  this  salt  gave  a  fine 
crimson  color.  Formiate  of  cinchonia  was  obtained  in  crystals, 
soluble  in  hot  and  cold  water,  and  gave  with  the  tests  the  same 
reactions  as  the  other  salts  of  cinchonia.  Formiate  of  morphia 
was  not  crystallizable,  but  only  formed  in  white  crusts,  and  gave 
the  fine  blue  color  with  sesquichloride  and  salts  of  the  sesqui- 
