62 
Exaynination  of  Citrates^  etc. 
( Am.  Jour.,  Pharm. 
t        Feb.,  1875. 
excess,  the  mixture  boiled  and  set  aside  for  twenty-four  hours.  The 
precipitate  is  then  washed,  on  a  tared  filter,  with  a  little  water  and  much 
dilute  alcohol,  dried  at  40°  to  50°  C,  and  weighed.  CaC^H^O(34HoO 
:  HAH,0„  :  :  I  :  0-577. 
Estimation  of  Tartaric  Acid  in  presence  of  Citric  Acid. — This  is  an 
especially  difficult  separation,  and  the  results  by  the  following  method 
are  only  approximate.  The  concentrated  solution  is  made  nearly  neu- 
tral, but  slightly  acid,  with  acetic  acid.  Alcohol  is  added,  short  of  pre- 
cipitation, and  then  concentrated  solution  of  potassium  acetate  in  slight 
excess.  The  precipitate  is  washed  with  alcohol,  on  a  tared  filter,  and 
dried  on  a  water-bath.  KHC^H^Og  :  Yif^^f^^  :  :  i  :  0797.  Sul- 
phates do  not  interfere  ;  but  if  they  preponderate,  the  first  washing  of 
the  precipitate  should  be  with  dilute  alcohol,  and,  after  weighing,  the 
precipitate  should  be  found  free  from  sulphates. 
Estimation  of  Citric  Acid  in  presence  of  Tartaric  Acid. — Obtain  the  cal- 
cium precipitate  by  the  directions  for  tartaric  acid  alone,  h  (drying  at 
about  50°  C).  With  another  portion  of  material  find  the  amount  of 
tartaric  acid  from  the  hydric  potassic  tartrate,  according  to  the  preced- 
ing paragraph.  Calculate  the  equivalent  calcium  tartrate  :  H.^C^H^Og 
:  CaC_(H^O,.4H20  :  :  i  :  1*733.  Subtract  this  from  the  weight  of  the 
calcium-tartrate  and  citrate-precipitate  obtained,  and  from  the  remainder, 
as  Q2i.^^f^~^.{l\{f^.^  calculate  the  citric  acid. 
The  foregoing  methods  have  been  gathered  from  various  authors,  in 
current  works,  and  the  writer  has  merely  succeeded  in  verifying  them, 
as  giving  (except  for  separation  of  citric  from  tartaric  acid)  close  results. 
I  have  also  tried  the  separation  of  citric  from  tartaric  acid,  as  calcium 
salts,  by  solubility  of  the  calcium  salt  in  potassa  solution,  with  the  fol- 
lowing (unsatisfactory)  results  : 
Took  0*450  grams  of  tartaric  acid  and  0*630  grams  of  (crystallized) 
citric  acid,  dissolved  in  water  ;  added  ammonia  to  a  very  slight  alkaline 
reaction,  and  then  calcium  chloride  in  excess,  boiling  the  precipitate 
for  a  long  time.  Washed  thoroughly,  on  a  filter,  with  hot  water  ;  the 
washings  continuing  to  contain  calcium.  Treated  thoroughly  with 
solution  of  potassa,  and  washed  the  residue  on  a  tared  filter,  and  dried 
below  100°  C.  The  weight  of  the  precipitate,  1-030  gram,  as  the 
hydrated  calcium  citrate,  Ca3  (CgH50,)2  2H2O,  corresponds  to  0*8 10 
gram  of  crystallized  citric  acid,  being  0"i8ogram  more  than  was  taken 
— an  increase  of  28  per  cent. 
2.  Analyses  of  a  few  Citrates  and   Tartrates  in  Market. — i.  H.  W. 
