422  Salicylic  Acid  and  Monad  Salts.  {AmsJeptr;Sarm" 
Three  molecules,  414  parts  of  salicylic  acid  requires  two  molecules, 
648  parts  of  the  citrate  for  perfect  and  permanent  solution.  This 
indicates  that  only  half  of  the  potassic  radicle  is  replaced  as  repre- 
sented by  the  following  equation  : 
2(K3Ci) + 3(  H  S1)=3(KS1) + K2H  Ci + KH2Ci. 
The  two  resulting  acid  citrates,  either  separately  or  conjointly,  form 
an  amorphous  mass  which  greatly  interferes  with  the  crystallization  of 
the  intermingled  salicylate.  It  is  however  readily  distinguishable 
under  the  micro-polariscope.  When  the  dry  residue  is  flooded  with 
sufficient  water  the  crystals  are  better  seen  along  the  margins  of  the 
liquid. 
POTASSIUM  TARTRATE. 
Salicylic  acid  and  normal  potassium  tartrate  react  upon  each  other 
molecule  for  molecule,  that  is,  in  the  proportion  of  138  parts  of  the 
first  and  235  parts  of  the  second,  according  to  the  following : 
K2T + HS1  =KS1 + K  HT. 
After  filtering  off  the  precipitated  acid  tartrate  the  salicylate  is  ob- 
tained in  a  practically  pure  solution.  Evaporated  on  a  slide,  the  salt 
crystallizes  mixed  with  an  occasional  rhomb  of  the  acid  tartrate. 
On  flooding  the  slide  with  water  the  tartrate  remains  and  becomes  very 
conspicuous.  It  also  polarizes,  but  incomparably  less  florid  than  the 
salicylate. 
ROCHELLE  SALT. 
One  molecule  or  282  parts  of  sodio-potassic  tartrate  reacts  with  one 
molecule  or  138  parts  of  salicylic  acid.    The  product  consists  practi- 
cally of  precipitated  acid  potassic  tartrate  and  a  solution  of  sodium 
salicylate.    The  result  is  expressed  by  the  equation : 
KNaT + HSl=NaSl + KHT. 
The  solution  dried  on  a  slide  gives  a  crystalline  residue  which, 
under  the  microscope,  is  shown  to  have  a  feathery  appearance.  In  the 
smaller  crystals  there  is  a  decided  tendency  to  radial  grouping.  When 
the  residue  is  flooded  with  water  a  due  proportion  of  rhombic  cream  of 
tartar  crystals  remain  and  an  occasional  short  prismatic  needle  of  acid 
sodium  tartrate  is  seen.  The  sodium  salicylate  soon  attaches  itself  to 
these  again,  and  whilst  completely  covering  them  wholly  confuses  it- 
self. The  salicylate  polarizes  finely  as  also  does  the  acid  sodium  tar- 
trate, but  in  much  smaller  degree.  A  solution  of  pure  sodium  salicy- 
late yields  chiefly  feathery  crystals  arranged  in  numerous  concentric 
rings.    In  each  ring  system  the  crystals  are  all  confined  to  rings,  but 
