TARTARIC  ACID  FROM  SUGAR  OF  MILK,  ETC. 
345 
from  the  juice  itself  would  have  involved  an  unnecessary  waste  of 
material  London  Pharm.  Journ.  May,  1860. 
ON  THE  FORMATION  OF  TARTARIC  ACID  FROM  SUGAR  OF 
MILK  AND  GUM. 
By  J.   VON  LlEBIG. 
When  a  mixture  of  one  part  of  sugar  of  milk,  two  and  a  half 
parts  of  nitric  acid,  sp.  gr.  1-32,  and  two  and  a  half  parts  of 
water,  is  moderately  heated,  carbonic  acid  and  gaseous  products 
of  the  decomposition  of  nitric  acid  are  disengaged,  and  there 
separates,  after  continuing  the  heat  for  some  time,  a  thick  white 
magma  of  mucic  acid.    Diluted  with  an  equal  volume  of  water, 
and  filtered  from  the  mucic  acid,  the  liquid  obtained  yields  a 
fresh  portion  of  mucic  acid  on  being  again  heated  with  one  fourth 
of  the  nitric  acid  before  employed.    The  whole  of  the  mucic  acid 
obtained  amounts  to  about  33  per  cent,  of  the  sugar  of  milk.  It 
follows  that  the  greater  part  of  the  milk  sugar  must  have  escap- 
ed in  the  form  of  the  gaseous  products  of  oxidation,  or  be  con- 
tained in  the  acid  mother  liquor,  from  which  the  mucic  acid  has 
been  deposited.    This  liquid  has  a  yellowish  color,  and  when 
concentrated  by  evaporation  yields  a  thick  acid  syrup,  which 
frequently  under  X0Qc  becomes  at  first  brown  and  then  black. 
When  the  mother  liquor,  from  the  mucic  acid,  and  the  washings 
are  mixed  and  boiled,  carbonic  acid  and  nitric  oxide  are  disen- 
gaged, and  the  liquid  becomes  dark  brown  ;  but  this  last  effect 
may  be  prevented   by  the  addition  from  time  to  time  of  more 
nitric  acid.    After  continuing  the  boiling  for  18  or  24  hours, 
the  liquid  no  longer  turns  brown  on  neutralising  with  potash. 
At  this  time  it  contains  a  large  proportion  of  tartaric  acid.  It 
is  now  concentrated  by  a  gentle  heat,  and  divided  into  two  parts  : 
one  is  saturated  with  potash,  and  the  two  are  then  poured  to- 
gether and  allowed  to  stand,  when  crystals  of  bitartrate  of  pot- 
ash are  deposited.    These  are  sometimes  mixed  with  needle-like 
crystals  of  saccharate  of  potash,  which,  being  more  soluble  than 
the  bitartrate,  may  be  easily  separated  by  dissolving  the  two  in 
as  small  a  quantity  of  boiling  water  as  possible,  and  quickly 
cooling  the  solution.    In  this  way  the  bitartrate  is  separated  in 
the  form  of  shining  crystalline  granules.    By  standing  longer, 
