454 
GlycerHv  of  Birch  Tar, 
(  Am.  Jour.Pharni 
\      Sept.,  1882. 
here  an  addition  of  some  washed  animal  eliarcoal),  and  then  filtered^ 
The  filtrate,  which  must  still  he  distincitly  aeid,  is  broui^ht  uj)  to  the 
original  volume  of  the  wine  with  water,  and  0*5  to  1  va.  of  a  eold 
saturated  solution  of  neutral  acetate  of  lead  added  and  very  briskly 
agitated.  The  lead  precipitate  contains  a  portion  of  the  malic  ac^id 
(another  portion  remains  dissolved  as  an  acid  salt  in  the  dilute, 
acid  liquid),  phosphoric  acid,  a  trace  of  sulphuric  acid,  tartaric  acid 
and  citric  acid.  It  is  filtered  off',  washed  wntli  cold  water,  placed 
together  with  the  filter  in  a  closed  retort  containing  water  saturated 
with  sulphuretted  hydi'ogen  and  energetically  shaken  and  thus  decom- 
posed. After  standing  some  time  the  perfectly  colorless,  clear  liquid, 
which  contains  the  above-mentioned  acids,  is  filtered  olf,  washed  with 
water  containing  sulphuretted  hydrogen,  the  sulphuretted  hydrogen 
driven  oft'  by  evaporation,  and  the  liquid,  amounting  to  about  15  (;e... 
made  faintly  alkaline  with  thin  milk  of  lime,  so  as  to  separate  ])h()s- 
phoric  acid,  then  filtered,  the  filtrate  acidulated  with  the  smallest  pos- 
sible quantity  of  acetic  acid,  and  by  standing  from  half  to  one  hour 
the  tartaric  acid  present  sufficiently  removed  as  tartrate  of  lime.  The 
liquid  is  then  evaporated  to  dryness  to  separate  free  acetic  acid,  the 
residue  taken  up  with  hot  w^ater,  and  this  concentrated  until  the  sepa- 
ration  of  the  crystalline  citrate  of  lime.  After  being  once  separated  it 
is  no  longer  soluble  in  hot  water;  it  is  filtered  off,  washed  hot,  dried 
and  weighed.  The  salt  has  the  composition  (Q^fyj\Q'A.:^-{-^\i.^O.  In 
this  way,  in  a  case  where  20  mg.  of  citric  acid  had  been  added  to  ti; 
wine  a  precipitate  corresponding  to  18  mg.  of  citric  acid  was  obtained.. 
In  a  specimen  of  commercial  tamarinds  13'5  per  cent,  of  citric  acid 
was  found. 
Most  of  the  natural  wines  tested  were  found  to  be  free  from  citrie 
acid.  Some  of  them  contained  traces;  as,  for  instance,  a  white  Alsace- 
wine  of  1878,  and  a  white  Italian  wine  of  1880.  But  the  amounts  of" 
citric  acid  in  these  wines  only  amounted  to  between  O'OOo  and  O'OO^ 
per  cent.— Jour  and  Trans.,  July  15,  1882;  Zeitsch.  f.  AnaL 
Chem.,  xxi,  43. 
Glycerite  of  birch  tar  has  been  successfully  used  in  eczema  by  E.. 
Johanson;  it  was  prepared  by  mixing  one  part  of  birch  tar  witli  eight 
parts  of  glycerin,  the  latter  previously  diluted  with  one-fifth  water, — 
Fhar.  Zeit  RussL,  No.  21. 
