Am.  Jour.  Pharm.  \ 
Jan.,  1877.  j 
Solvents  of  Salicylic  Acid. 
27 
that  of  either  borax  or  ammonium  citrate.  One  part  of  salicylic  acid 
requires 
2  parts  of  phosphate  to  form  a  solution  with  50  parts  water. 
z'25  «  «  25  " 
2-5!  tt  «  a  I2-5  « 
Solutions  1  and  2  are  colorless,  but  the  strongest  solution  has  a 
slight  pink  tint  (characteristic  of  salicylic  salts).  Diluted  with  water, 
ferric  chloride  added  in  excess  gives  a  purple  red  solution,  which  also 
indicates  the  existence  of  a  salicylic  salt,  since  whilst  free  salicylic  acid 
strikes  a  purple  color  with  ferric  chloride,  its  salts  give  a  deep-red  color- 
ation with  this  reagent.  No  phosphoric  acid,  however,  is  liberated,  for 
a  single  drop  of  the  dilute  acid  added  to  the  solution  causes  a  precipita- 
tion of  salicylic  acid. 
Ammonium  Citrate. — I  first  ascertained,  by  experiment,  that  this 
citrate,  whilst  increasing  the  solubility  of  salicylic  acid  in  water  to  a 
much  greater  extent  than  sodium  citrate,  yet  possesses  no  advantages 
over  potassium  citrate,  and  as  this  latter  was  more  convenient  for  my 
purpose,  I  have  employed  it  in  preference. 
Table  of  solubility  of  salicylic  acid  in  potassium  citrate  solution  : 
Salicylic  Acid  1  Citrate    '75  Water  100 
"  1  "  i-o 
"  1  "  115 
«  1  "  1-25 
it 
5° 
25 
20 
12-5 
7-5 
1  "  1*4 
«  I  "  1.5 
A  stronger  solution  than  the  last  solidfies  upon  cooling,  but  the 
nature  of  the  mass  I  have  not  yet  ascertained.  It  gives  reactions  indi- 
cative of  free  and  combined  salicylic  acid  and  of  combined  citric  acid, 
but  not  of  free  citric  acid.  An  alcoholic  solution  of  potassium  salicy- 
late, mixed  with  a  similar  solution  of  citric  acid,  gives  a  precipitate  of 
potassium  citrate,  which  readily  dissolves  on  the  addition  of  a  little 
water,  and  the  solution  thus  formed  is  miscible  with  water,  without 
precipitation  of  salicylic  acid.  1  dram  Acid.  Salicylic,  3J  drams.  Sp. 
Vin.  Rect.,  1  dram.  Pot.  Cit.  and  3J  drams.  Water,  form  a  solution 
miscible  with  water  in  all  proportions,  and  2  drams  of  which  contain 
15  grains  of  the  acid.  In  this  solution  diluted,  acetic  acid  gives  no 
precipitate,  citric  acid  causes  a  precipitate  to  form  slowly,  mineral  acids 
throw  down  the  salicylic  acid  instantly  ;  ferric  chloride  colors  the  fluid 
purple-red. 
1  Three  drams  would  contain  a  full  dose  (fifteen  grains  nearly)  of  salicylic  acid. 
