424  Salicylic  Acid  and  Monad  Salts.  {AmsiXimrm* 
two  molecules  of  the  citrate  reacted  with  one  molecule  of  the  salicylic 
acid,  according  to  the  following  equation  : 
2(Na2HCi)+HSl=NaSl+Na2HCi+NaH2Ci. 
It  will  be  seen  the  extra  molecule  of  disodic  citrate  is  apparently 
superfluous  as  it  reappears  intact  in  the  second  member  of  the  equa- 
tion. It  is  nevertheless  somehow  essential  to  the  result,  as  all  the 
salicylic  acid  can  only  be  dissolved  by  the  whole  amount.  The  solu- 
tion leaves  elegant  crystals  on  the  slide,  which  are  simply  magnificent 
under  the  microscope.  They  must  be  viewed  with  very  low  powers, 
owing  to  their  unusual  size.  They  now  closely  resemble  the  potassium 
salicylate,  as  formed  from  the  acetate.  They  also  lack  the  ringed  ar- 
rangement. 
SODIUM  PHOSPHATE. 
Salicylic  acid  reacts  on  disodic  phosphate  molecule  for  molecule 
according  to  the  following  equation : 
Na2HP04+HSl=NaSl+NaH2P04. 
The  solution  yields  a  dry  residue  in  which  the  salicylate  does  not 
appear  to  advantage.  It  does  not  possess  a  particularly  agreeable 
taste. 
SODIUM  PYROPHOSPHATE. 
One  molecule  or  446  parts  of  sodium  pyrophosphate  dissolves  two 
molecules  or  276  parts  of  salicylic  acid,  and  the  reaction  is  indicated 
as  follows  : 
Na4P207+2(HSl)=2(NaSl)+Na2H2P207. 
The  product  gives  rather  better  results  under  the  microscope  than 
the  phosphate  mixture.    It  also  has  a  more  pleasant  taste. 
SODIUM  BORATE. 
Two  molecules  or  276  parts  of  salicylic  acid  are  dissolved  by  one 
molecule  or  382  parts  of  sodium  pyroborate  as  shown  by  the  follow- 
ing equation ; 
Na2B407 + 2(HSl)=2(i\aSl)  +  H2B407. 
This  result  is  rather  remarkable.  It  differs  from  all  the  other  cases 
in  that  the  pyroboric  acid  is  wholly  replaced  and  thus  set  free.  On 
evaporation,  a  pasty,  transparent  residue  remains.  Under  the  micro- 
scope no  satisfactory  view  is  obtained,  as  the  salicylate  is  completely 
obscured  by  the  amorphous  and  extremely  soluble  pyroboric  acid. 
The  solution  has  a  very  nauseous  taste. 
