1 1 6  Hydrobromic  Acid.  {^'i^l'Sjt0' 
again,  acetic  acid  and  water  make  their  appearance.  This  wonderful 
metamorphosis  of  these  carbon  compounds  occurs  in  the  cells  and 
tissues  of  plants  and  animals.  Acetic  acid  is  found  in  small  quantities 
in  juices  of  plants  and  animal  fluids. 
Formic  acid  exists  in  red  ants,  and  by  making  them  travel  over 
moistened  litmus  paper  it  will  redden  from  the  acid  secreted  by  them  ; 
hence  the  name  of  formic  acid  from  the  Latin  Formica.  For  preparing 
the  acid  the  process  known  as  Bertholet's  was  employed,  and  proved 
satisfactory.  Oxide  of  carbon  is  produced  from  oxalic  acid,  and  trans- 
formed into  formic  acid  under  the  influence  of  water. 
Place  into  a  retort  250  parts  of  syrupy  glycerin,  38  to  50  parts  of 
water,  and  250  parts  of  oxalic  acid  ;  heat  up  to  ioo°C.  The  oxalic 
acid  is  destroyed,  evolving  carbonic  acid,  while  all  of  the  oxide  of  car- 
bon combines  with  the  elements  of  water.  After  ten  hours  all  the 
oxalic  acid  is  decomposed,  and  a  small  quantity  of  water  charged  with 
formic  acid  has  distilled  over  ;  the  glycerin  and  the  largest  part  of 
formic  acid  remain  in  the  retort.  Add  8  parts  more  water,  and  distil 
at  the  temperature  of  I20°C,  adding  water  as  long  as  the  distillate  is 
acid.  The  glycerin  remains  intact,  and  can  be  used  over.  It  retains 
the  formic  acid  from  the  water,  and  can  be  heated  without  fear. 
This  acid  is  colorless,  sour  and  of  a  pungent  taste. 
NOTE  ON  HYDROBROMIC  ACID. 
By  Edward  R.  Squibb,  M.D.1 
The  potassium  salt  is,  of  all  the  bromides,  the  most  commonly  used, 
and  its  doses  to  obtain  given  effects  are  best  established.  Hence  if 
this  salt  be  used  as  a  standard  for  hydrobromic  acid  as  it  is  for  other 
bromides,  and  the  acid  be  adjusted  in  strength  so  as  to  bear  some  easily 
remembered  relation  of  its  bromine  constituent  to  the  potassium  salt, 
a  base  or  starting  point  would  be  established  for  its  general  and  accu- 
rate use,  whether  the  bromine,  when  combined  with  hydrogen,  should 
prove  more  active  than  when  combined  with  potassium  or  not.  Then 
as  the  potassium  salt  contains,  in  round  numbers,  say  68  per  cent,  of 
bromine,  a  solution  of  hydrobromic  acid  containing  also  68  per  cent, 
of  bromine  would  have  the  same  bromine  value,  though  not  necessarily 
1  From  a  paper  read  before  the  Medical  Society  of  the  State  of  New  York,  and 
communicated  by  the  anthoi. 
