256 
Citro-Phosphate  of  Sodium. 
\m.  .Jonr.  Pharm 
May,  1896. 
SOLUTION  OF  CITRO-PHOSPHATE  OF  SODIUM^ 
Sodium  phosphate  has  long  been  known  as  a  hepatic  stimulant 
and  purgative,  when  given  in  doses  of  1  or  2  drachms;  and 
within  a  year  or  so  there  have  been  placed  on  the  pharmaceutical 
market  of  the  United  States  several  preparations  which  are  stated 
to  be  solutions  of  sodium  phosphate.  One  of  these  solutions  is 
known  as  "  Melachol,"  and  its  advertisement  claims  every  fluid 
drachm  of  it  to  contain  85  grains  of  the  combined  sodium  phos- 
phate, citric  acid  and  sodium  nitrate.  The  other  solutions  are  said 
to  contain  from  60  to  85  grains  of  sodium  phosphate  in  each 
fluid  drachm.  The  United  States  Pharmacopoeia,  in  describing 
sodium  phosphate,  says :  "  when  heated  to  about  400  C.  the  salt 
fuses,  yielding  a  colorless  liquid ;"  and  it  is  well  known  that,  on 
cooling,  the  liquid  congeals  to  a  crystalline  mass.  The  official  state- 
ment of  solubility  reads :  "  soluble  in  5-8  parts  of  water  at  150  C.,. 
and  in  somewhat  less  than  1-5  parts  of  boiling  water;"  and  Mulder, 
in  1864,  gave  the  solubility  as  1  in  2-5  parts  of  water  at  300  C. 
Thus  we  see  that  these  solutions  are  said  to  contain  more  sodium 
phosphate  than  could  be  kept  in  solution  in  water  at  ordinary 
temperatures,  and  that  permanent  liquefaction  by  heat  is  impossible. 
Therefore,  if  the  sodium  phosphate  is  the  chief  medicament  and  the 
other  substances  are  of  minor  importance  as  medicinal  agents,  they 
must  be  used  either  to  help  make  it  possible  to  get  so  concentrated 
a  solution  of  sodium  phosphate,  or  to  mask  the  alkaline  taste  of  the 
latter,  and  thereby  render  it  more  acceptable.  In  order  to  ascertain 
whether  such  a  concentrated  solution  of  sodium  phosphate  could  be 
prepared,  the  writer  made  some  experiments  with  the  three  substances. 
He  has  found  that  100  parts  of  sodium  phosphate  and  10  parts  of 
citric  acid,  when  shaken  or  triturated  together,  liquefy;  that  100 
parts  of  sodium  phosphate  and  5  parts  of  sodium  nitrate  under  the 
foregoing  conditions  become  semi-solid ;  and  that  5  parts  of  sodium 
nitrate  can  be  added  to  the  liquid  resulting  from  the  mixing  of  the 
sodium  phosphate  and  citric  acid  without  causing  it  to  solidify. 
The  solution  that  was  found  to  correspond  in  specific  gravity, 
acidity  (titrated  as  citric  acid)  and  amount  of  phosphoric  anhydride 
to  "  Melachol,"  was  the  product  of  the  following  formula : 
By  Wiuiam  C.  Wescott,  Ph.G. 
Sodium  phosphate,  crystallized 
Sodium  nitrate  
Citric  acid   
Grammes. 
.  IOO 
2 
